Rancho Cucamonga City Council
January 21, 2026

2026-01-21- Regular Meeting – Correspondence Received for Public Hearing Item G1

-----Original Message-----
From: John Spencer <[email protected]>
Sent: Tuesday, January 20, 2026 4:50 PM
To: City Clerk <[email protected]>
Subject: Etiwanda Heights Conservation Plan

Members of Rancho Cucamonga City Council, Stop the overbuilding of Rancho Cucamonga! 3000 homes in Etiwanda Heights is horrible to imagine…6000 is insane!! This will damage our beautiful community! Traffic is already terrible during rush hour. What about fire safety? Are you trying to destroy what is left of this wonderful area that we live in?
I beg you to vote NO ON ETIWANDA HEIGHTS CONSERVATION PLAN! Tax Payer and Voter,

Jackie Spencer
12982 Cherokee Rd.,
Rancho Cucamonga
Sent from my iPad

2026-01-21- Regular Meeting – Correspondence Received for Public Hearing Item G1

2026-01-21- Regular Meeting – Correspondence Received for Public Hearing Item G1 Hello Mayor, Council Members, and Planning Commission,
I am a Rancho Cucamonga citizen living in close proximity to the Etiwanda Heights Neighborhood. When the city asked for citizens to participate in the initial EHNCP workshops, forums, and surveys, I wholeheartedly participated, believing my input would make a difference. I recall when plans were presented for housing of up to 3,000 single family homes and no multi-family units, thinking one day we may want to move into a new home in this neighborhood. That dream is now looking like a nightmare given the proposed amendment to the Etiwanda Heights Neighborhood area density.

This area, surrounded by Banyan, Wilson, and Rochester's single lanes in each direction, a community college, 2 high schools, and three elementary schools, with high volume car and bus traffic feeding all of these schools, and parents, grandparents, and caregivers walking students to school, is absolutely not fit to accommodate the significantly increased traffic that would inevitably come by increasing the density of this neighborhood and allowing multi-family unit housing. Going from 3,000 single family homes to over 6,000 without a doubt increases the volume of cars flooding the streets. Communication put out by the city of RC in response to the Dec. 10, 2025 Planning Commission Public Comments states that "street layout was designed intentionally to avoid single-access patterns, such as cul-de-sacs or dead-end streets, which can concentrate traffic onto one road," however the opposite is true as was seen in the map shown by the Previti Group at the Planning Commission Public Hearing, in which they showed Planning Area 2 with essentially 35 cul-de-sacs and Planning Area 1 with at least 8, which is what motor court homes create-- cul-de-sacs of shared motor courts with everyone accessing their garage space through the same driveway. Furthermore, the communication from the city states, "the plan includes multiple connections within the neighborhood, allowing traffic to flow in different directions and helping reduce pressure on any single roadway." However, the concern is not merely the traffic within the Etiwanda Heights Neighborhood. The concern is the traffic flowing out of the neighborhood onto the surrounding streets of Banyan, Wilson, Rochester (again, all single lanes in each direction) as well as Milliken and Day Creek.

I am including a video that shows what current traffic is like coming out of John L. Golden Elementary School's drop-off line. The cars shown in the drop off lines and parking lot are cars that have already dropped off their students but simply cannot get out of the campus drop off line and parking lot due to the backed up traffic on Banyan that goes all the way down to Los Osos High School. I will also share two more videos in two separate emails from two other days that show more examples of this current traffic congestion that would only be made impossible by allowing more than double the number of originally proposed housing units in the EHNCP .

Beyond this, and even more importantly than the issue of traffic, which affects our daily quality of life, is the issue of emergency evacuation in the event of a wildfire, which is not a quality of life issue, but an issue of life itself, or perhaps death. According to Calmatters.org, "of all the structures destroyed by wildfire between 1985 and 2013, more than 80% were in [the] fire-prone zone" known as the wildland-urban interface--"the hillsides, ravines, and canyons where... residential development meets and merge[s] with the state's forests, scrublands, and grasses. " This is exactly what the Etiwanda Heights Neighborhood is- housing development abutting a preserve filled with natural grasses and shrubs. This neighborhood and its surrounding neighborhoods all the way to the 15 freeway and beyond, along the foothills, are in a CalFire designated Very High Fire Hazard Severity Zone. While the developer wants to convince us that fire hazards will not be an issue because new housing will meet the latest fire- safety standards, this amendment will do the very opposite of observing fire-safety standards by increasing density with multi-family units. According to research by the Insurance Institute for Business and Home Safety, "in high density neighborhoods during a severe wildfire, extreme burning conditions lead to a higher number of structures to burn. Once a few buildings ignite, a domino effect occurs, with fire spreading rapidly until the extreme burning conditions, usually driven by strong winds, diminish. Under extreme wildfire conditions, defending structures becomes harder due to safety concerns for both firefighters and the public. During these conditions, the main way fires spread is through wind-driven flames jumping from building to building." Furthermore, increasing the housing density increases population density, which increases the amount of fuel in that neighborhood to feed fires... more cars with both fuel and electric car batteries, more outdoor furniture, more umbrella shades in backyards, more sheds storing flammables, more propane tanks to fuel BBQs. People will plant gardens and add landscaping that can further fuel fires. And even with fire hard homes, every home can only withstand so much heat before it crumbles to the 2,200 degrees Fahrenheit that a wildfire can reach in extreme conditions. We know that wind is the primary driver of wildfire spread and that our area faces extreme winds every year. It is also well established that embers can be carried miles away due to extreme winds, and according to the USDA Forest Service, "homes are much more likely to burn due to small flying embers than by contact with large flames. " This neighborhood is well within the radius in which embers would spread from a wildfire breaking out in the preserve.

Combining the above discussed issues of traffic and high wildfire risk, evacuation becomes impossible, leaving residents unable to escape the rapidly burning flames and spreading wildfires that cannot be prevented by building homes according to fire-safety standards when they are up against flying embers carried by extreme winds. The number of cars that would flood the single lanes of Banyan, Wilson, and Rochester and two southbound lanes of Milliken and Day Creek, would overwhelm the streets leading to gridlock and the inability to escape. The communication from the city in response to the 12/10/25 Planning Commission Public Comments suggests a "likelihood that sheltering in place is the safest option under certain conditions and may reduce the need for large- scale evacuations. " You cannot bank on sheltering in place as the safest option given the above mentioned risks in our neighborhoods. You must have a realistic plan to carry out a large-scale evacuation if and when that call is made in order to save the lives of this city's residents.

Please do the right thing for the future citizens in the Etiwanda Heights Neighborhood and the current citizens in the surrounding neighborhoods. Please do the right thing for the firefighters protecting these neighborhoods.

Please do the right thing in keeping promises that were made and honoring the input that citizens provided from the beginning of this process back in 2018. Please vote no on this amendment.

Sincerely,
Alicia Mosley

VIDEO ATTACHMENT: This video shows morning backup from westbound Banyan traffic on 1/20/26

J
anuary 20, 2026
VI

A EMAIL
L. Dennis Michael, Mayor
Lynne Kennedy, Mayor Pro Tem
Ryan Hutchison, Council Member
Kristine Scott, Council Member
Ashley Stickler, Council Member
10500 Civic Center Drive
Rancho Cucamonga, CA 91730
[email protected]
[email protected]
[email protected]
R
e: Comment on Addendum to EIR for the Etiwanda Heights Neighborhood and Conservation Plan, January 21, 2026, City Council Meeting, Agenda Item No. G1
D
ear Mayor Michael, Mayor Pro Tem Kennedy, and Honorable Councilmembers:

T
his comment is submitted on behalf of Supporters Alliance for Environmental Responsibility (“SAFER”) regarding the amendment to the Etiwanda Heights Neighborhood and Conservation Plan and associated Addendum to the EIR (“Project”), to be heard at the City Council’s Meeting on January 21, 2026.

S
AFER objects to the City’s reliance on an Addendum to the 2019 Etiwanda Heights Neighborhood and Conservation Plan EIR. Under the California Environmental Quality Act (“CEQA”), an addendum is not appropriate because the there is new information available since the certification of the 2019 EIR indicating new significant impacts. SAFER requests that the City Council refrain from taking any action on the Project at this time and, instead, direct staff to prepare an initial study for the Project, followed by a project-specific EIR or negative declaration as required by CEQA.

P

ROJECT DESCRIPTION
T
he Project amends the Etiwanda Heights Neighborhood and Conservation Plan, including the 790-acre “Neighborhood Area” in the City of Rancho Cucamonga. The proposed amendment includes a maximum density and additional building designs and standards to meet such density. The Project also includes two tentative tract maps and 2026-01-21- Regular Meeting – Correspondence Received for Public Hearing Item G1 Comment on Addendum to Etiwanda Heights Neighborhood and Conservation Plan EIR January 20, 2026 City Council Meeting

modified site plants for Planning Areas 1 and 2 which are proposed for near-term development.

LEGAL STANDARD

CEQA contains a strong presumption in favor of requiring a lead agency to prepare an EIR. This presumption is reflected in the fair argument standard. Under that standard, a lead agency must prepare an EIR whenever substantial evidence in the whole record before the agency supports a fair argument that a project may have a significant effect on the environment. (Pub. Res. Code § 21082.2; Laurel Heights Improvement Ass’n v. Regents of the University of California (1993) (“Laurel Heights II”) 6 Cal.4th 1112, 1123; No Oil, Inc. v. City of Los Angeles (1974) 13 Cal.3d 68, 75, 82; Quail Botanical Gardens v. City of Encinitas (1994) 29 Cal.App.4th 1597, 1602.) The City has never prepared an EIR for this Project. Even the 2002 document that the City is purporting to rely upon was an MND, not an EIR.

Preparation of an Addendum Under CEQA

Here, the City has prepared an addendum to the previously certified 2019 EIR.

Pursuant to the CEQA Guidelines, an addendum to a previous EIR is proper only where “some changes or additions are necessary but none of the conditions described in Section 15162 calling for preparation of a subsequent EIR have occurred.” (14 CCR § 15164(a).) An addendum is not appropriate when:

(1) Substantial changes are proposed in the project which will require major revisions of the previous EIR or negative declaration due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects;
(2) Substantial changes occur with respect to the circumstances under which the project is undertaken which will require major revisions of the previous EIR or Negative Declaration due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects; or
(3) New information of substantial importance, which was not known and could not have been known with the exercise of reasonable diligence at the time the previous EIR was certified as complete or the negative declaration was adopted, shows any of the following:
(A) The project will have one or more significant effects not discussed in the previous EIR or negative declaration;
(B) Significant effects previously examined will be substantially more severe than shown in the previous EIR;
(C) Mitigation measures or alternatives previously found not to be feasible would, in fact, be feasible and would substantially reduce one or more significant effects of the project, but the project proponents decline to adopt the mitigation measure or alternative; or
Comment on Addendum to Etiwanda Heights Neighborhood and Conservation Plan EIR January 20, 2026 City Council Meeting

(D) Mitigation measures or alternatives which are considerably different from those analyzed in the previous EIR would substantially reduce one or more significant effects on the environment, but the project proponents decline to adopt the mitigation measure or alternative.

(14 CCR § 15162.)

DISCUSSION

I. New Information of Substantial Importance Demonstrates That the Project Will Have Significant Indoor Air Quality Impacts Not Analyzed in the 2019 EIR.

Since 2019, there is new information regarding the health risks associated with formaldehyde-emitting building materials that has been made available. This new information demonstrates that even if the Project complies with applicable building material regulations, a significant health risk remains that would affect residents of the Project through indoor formaldehyde emissions.

Formaldehyde is a known human carcinogen. Many composite wood products typically used in residential building construction contain formaldehyde-based glues which off-gas formaldehyde over a very long time period. The primary source of formaldehyde indoors is composite wood products manufactured with urea-formaldehyde resins, such as plywood, medium density fiberboard, and particle board. These materials are commonly used in residential and building construction for flooring, cabinetry, baseboards, window shades, interior doors, and window and door trims. Given the prominence of materials with formaldehyde-based resins that will be used in constructing the Project, there is a significant likelihood that the Project’s emissions of formaldehyde to air will result in very significant cancer risks to future residents and workers in the buildings. Even if the materials used within the buildings comply with the Airborne Toxic Control Measures (ATCM) of the California Air Resources Board (CARB), significant emissions of formaldehyde may still occur.

The residential homes will have significant impacts on air quality and health risks by emitting cancer-causing levels of formaldehyde into the air that will expose residents to cancer risks well in excess of SCAQMD’s threshold of significance. A 2020 study by Singer et al. (attached as Exhibit A) measured formaldehyde levels in new structures constructed after the 2009 CARB rules went into effect. Even though new buildings conforming to CARB’s ATCM had a 30% lower median indoor formaldehyde concentration and cancer risk than buildings built prior to the enactment of the ATCM, the levels of formaldehyde will still pose cancer risks greater than 100 in a million, well above the 10 in one million significance threshold established by the SCAQMD.

Based on expert comments submitted on other similar projects and assuming all the Project’s residential building materials are compliant with the California Air Resources Board’s formaldehyde airborne toxics control measure, future residents using the Project will Comment on Addendum to Etiwanda Heights Neighborhood and Conservation Plan EIR January 20, 2026 City Council Meeting

be exposed to a cancer risk from formaldehyde greater than the SCAQMD’s CEQA significance threshold for airborne cancer risk of 10 per million.

The City has a duty to investigate issues relating to a project’s potential environmental impacts. (See County Sanitation Dist. No. 2 v. County of Kern (2005) 127 Cal.App.4th 1544, 1597–98. [“[U]nder CEQA, the lead agency bears a burden to investigate potential environmental impacts.”].) This is especially true for toxic air contaminants such as formaldehyde. The proposed Project will have significant impacts on air quality and health risks by emitting cancer-causing levels of formaldehyde into the air that will expose future residents to cancer risks in excess of SCAQMD’s threshold of significance for cancer health risks of 10 per million.

Currently, the City does not have any idea what risk will be posed by formaldehyde emissions from the Project or the residences. As a result of this significant effect impact, which could not have been known when the 2019 EIR was published, the Project may not rely upon Section 15162 to forego the preparation of a supplemental EIR or at least a negative declaration for the Project.

This indoor air quality impact could not have been known until 2020 when the study was published showing that buildings using composite wood products that comply with the CARB formaldehyde standards vastly exceed CEQA significance thresholds for cancer risk. (Exhibit A.) Therefore, this impact was not known and could not have been known when the 2019 EIR was approved. When scientific information was not available at the time of prior CEQA review, more recent studies showing that a project may have more serious human health or environmental impacts constitute significant new information requiring a subsequent EIR. (Security Envt'l Sys. v South Coast Air Quality Mgmt. Dist. (1991) 229 Cal.App.3d 110, 124; Meridian Ocean Sys. v. State Lands Com. (1990) 222 Cal.App.3d 153, 169). As such, an addendum is improper and subsequent environmental review is required.

CONCLUSION

For the reasons set forth above, supplemental CEQA review is required for the Project because new information of substantial importance has become available demonstrating that that project will result in new significant impacts and require improved mitigation measures.

Sincerely,

Rebecca Davis
LOZEAU | DRURY LLP

EXHIBIT A
Lawrence Berkeley National Laboratory
LBL Publications
Title
Indoor air quality in California homes with code‐required mechanical ventilation Permalink
https://escholarship.org/uc/item/5284d4tk
Journal
Indoor Air, 30(5)
ISSN
0905-6947
Authors
Singer, Brett C
Chan, Wanyu R
Kim, Yang‐Seon
et al.

Publication Date
2020-05-12
DOI

10.1111/ina.12676

Peer reviewed
eScholarship.org Powered by the California Digital Library University of California
IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 1
Indoor Air Quality in California Homes with Code-Required Mechanical Ventilation 1 Brett C. Singer1, Wanyu R. Chan1, Yang-Seon Kim1,2, Francis J. Offermann3, Iain S. Walker1 2 1 Residential Buildings Systems Group and Indoor Environment Group, Lawrence Berkeley 3 National Laboratory, Berkeley, California, USA 4
2 Department of Mechanical Engineering, Wichita State University, Wichita, Kansas, USA 5 3 Indoor Environmental Engineering, San Francisco California, USA 6 Acknowledgements 7
This work was supported by the California Energy Commission through Contract PIR-14-007 8 and the U.S. Department of Energy Building America Program via Contract DE-AC02-9 05CH11231. The Southern California Gas Company (SoCalGas) provided direct funding to the 10 Gas Technology Institute (GTI) and staff resources to support an online survey and field data 11 collection. The Pacific Gas & Electric Company (PG&E) funded Misti Bruceri & Associates 12 (MBA) to provide a field technician. SoCalGas and PG&E deployed Gas Service Technicians to 13 conduct appliance safety inspections in study homes. Data collection in homes was conducted by 14 Luke Bingham, Erin Case, and Shawn Scott of GTI; Guy Lawrence of MBA; Eric Barba, Mary 15 Nones, Ara Arouthinounian, and Ricardo Torres of SoCalGas; and Woody Delp of LBNL. Rick 16 Chitwood assisted with data collection and guidance on measuring airflow in supply ventilation 17 systems. Max Sherman (retired from LBNL) helped develop the project and served as the initial 18 Principal Investigator. Genese Scott of SoCalGas helped with online survey recruitment. Marion 19 Russell of LBNL led the chemical analysis of air samples. Kelly Perce transferred survey and 20 activity log data from paper to the survey database. The CalCERTS and CHEERS organizations 21 provided Title 24 compliance records for many study homes. Neil Leslie, Larry Brand, and Rob 22 Kamisky of GTI provided management support. 23
24 25
IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 2
Abstract 1
Data were collected in 70 detached houses built in 2011-2017 in compliance with the mechanical 2 ventilation requirements of California’s building energy efficiency standards. Each home was 3 monitored for a one-week period with windows closed and the central mechanical ventilation 4 system operating. Pollutant measurements included time-resolved fine particulate matter (PM2.5) 5 indoors and outdoors and formaldehyde and carbon dioxide (CO2) indoors. Time-integrated 6 measurements were made for formaldehyde, NO2 and nitrogen oxides (NOX) indoors and 7 outdoors. Operation of the cooktop, range hood and other exhaust fans was continuously 8 recorded during the monitoring period. One-time diagnostic measurements included mechanical 9 airflows and envelope and duct system air leakage. All homes met or were very close to meeting 10 the ventilation requirements. On average the dwelling unit ventilation fan moved 50% more 11 airflow than the minimum requirement. Pollutant concentrations were similar or lower than those 12 reported in a 2006-2007 study of California new homes built in 2002-2005. Mean and median 13 indoor concentrations were lower by 44% and 38% for formaldehyde and 44% and 54% for 14 PM2.5. Ventilation fans were operating in only 26% of homes when first visited and the control 15 switches in many homes did not have informative labels as required by building standards. 16 Keywords: ASHRAE 62.2, Healthy Efficient New Gas Home Study, Carbon dioxide, Fine 17 particulate matter, Formaldehyde, Nitrogen dioxide 18
Practical Implications 19
High performance home standards and building codes and regulations require mechanical 20 ventilation equipment to help manage moisture and air pollutants emitted indoors. This paper 21 demonstrates the success of a new construction residential ventilation requirement instituted in 22 the state of California in 2008, with almost all studied homes having compliant ventilation 23 equipment. The study found that the combination of mechanical ventilation and implementation 24 of a standard that reduced the allowable formaldehyde emissions from manufactured wood 25 products resulted in formaldehyde concentrations that were lower by 44% and 38% at mean and 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 3
median levels than in homes built prior to the standards. This study affirms that new homes can 1 be built to stringent efficiency standards while maintaining indoor air quality. 2

1. Introduction 3
Since 2008, California’s statewide residential building code has included requirements for 4 mechanical ventilation to protect indoor air quality (IAQ). Ventilation requirements were 5 implemented to mitigate any negative impacts of reducing uncontrolled air infiltration by 6 envelope air-sealing to reduce energy use. Lower air infiltration reduces dilution of pollutants 7 emitted inside the home, leading to higher concentrations if no other actions are taken. Although 8 mechanical ventilation in new homes has become commonplace in many developed countries, it 9 is uncommon in the U.S., particularly in single-family dwellings. Many state and local building 10 codes in the U.S. have implicitly relied on natural ventilation through leaky envelopes or for 11 occupants to manage IAQ using natural ventilation. 12
The presumption that occupants effectively utilize natural ventilation to manage moisture and 13 chronic exposure to formaldehyde and other pollutants from indoor sources in homes was 14 examined in two large studies conducted in California in the mid-2000s. In 2003, a mail-based 15 survey was sent to a statewide representative sample of homes built in 2002-2003 to query IAQ 16 satisfaction, ventilation practices, activities, and equipment use that can impact IAQ1. Based on 17 self-reported window use, the researchers assessed that most homes were substantially under-18 ventilated relative to the target of 0.35 h-1, from the ASHRAE 62-1999 ventilation standard. 19 The California New Home Study (CNHS), conducted in 2006-2007, collected data in 108 homes 20 built in 2002–20052. The study included a thorough characterization of the building and thermal 21 and mechanical equipment; measurements of envelope and garage-to-house air leakage; an 22 occupant questionnaire that covered many of the same topics as the earlier mailed survey; 23 monitoring of window use over a week; and measurements of air exchange and various IAQ 24 parameters over a single 24-hour period. Sampling was roughly split between winter and summer 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 4
and between Northern and Southern California. Monitoring was repeated in 4 homes to 1 investigate day-to-day and seasonal variability. The study found that actual window use differed 2 from what participants reported generally for the season in which measurements were made (i.e., 3 52% under-reported and 8.3% over-reported), indicating that self-reported window use in the 4 mailout survey may have been biased low. The field study also found that air exchange rates 5 (AERs) in the majority of new homes were below the target of 0.35 h-1 and that formaldehyde 6 was substantially above state exposure guidelines in almost all homes. The results of these two 7 studies suggested that new homes were not being adequately ventilated and that relying on 8 occupants and natural ventilation is not an acceptable approach. 9 Starting with the 2008 statewide Title 24 Building Standards, California instituted mechanical 10 ventilation requirements that were a hybrid of the requirements in the 2007 and 2010 versions of 11 the ASHRAE Standard 62.2 for residential ventilation3. The California standard required exhaust 12 fans in the kitchen and every bathroom and general ventilation for the dwelling unit that could be 13 satisfied with a continuous or intermittent system, utilizing exhaust, supply or balanced airflows. 14 A severe slowdown in new home starts in 2008-2010 delayed implementation as most homes 15 built during these years had been approved under the prior building code. The ventilation 16 requirements were not fully incorporated until at least 2010. 17 The Healthy Efficient New Gas Home (HENGH) study, described herein, was performed to 18 evaluate IAQ in California homes built to meet the 2008 building standards for ventilation. The 19 study focused on homes with natural gas because the sponsoring research program is financed by 20 a surcharge on investor-owned, gas utility customers and because gas cooking burners are an 21 important source of air pollutants4, 5. The study included a web-based survey of homes built since 22 2002, a simulation-based study of the energy impacts of ventilation, and the field study described 23 in this paper. A report summarizing results of all three component studies is available6. 24 This paper presents the methods and results of the HENGH field study and compares findings 25 from homes built with mechanical ventilation in 2011-2017 to the CNHS homes built in 2002-26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 5
2005 mostly without mechanical ventilation. Homes studied in HENGH also were built with 1 materials that complied with an air toxic control measure (ATCM) for composite wood products7 2 that was implemented to reduce formaldehyde emissions. 3 The study goal was to provide empirical evidence of the impacts of ventilation and emission 4 standards in the most populous U.S. state. Findings may inform other states and nations 5 considering standards for residential mechanical ventilation. 6

2. Methods 7

2.1. Field Study Overview 8
Overview of Data Collection in Homes. The study was designed to assess how homes were 9 meeting the mechanical ventilation requirements and how the installed ventilation equipment 10 impacts indoor air quality. The study sought to characterize performance of installed equipment; 11 quantify the use of mechanical ventilation, gas cooking appliances and equipment that can 12 impact IAQ; measure key IAQ parameters over a weeklong monitoring period; and obtain data 13 from building occupants on IAQ and comfort satisfaction and IAQ-relevant activities. A core 14 goal was to evaluate IAQ in homes employing general (dwelling unit) mechanical ventilation but 15 not natural ventilation because the previous studies showed that many California homes do not 16 routinely open windows or doors for natural ventilation during one or more seasons of the year. 17 The study protocol was approved by the LBNL institutional review board. Methods are 18 summarized in ensuing subsections and detailed protocols are available 8. 19 Each study home was visited three times. On the first visit, the field team obtained written 20 consent, confirmed that code-required ventilation equipment was present and operable, and 21 started to record house, appliance, and mechanical equipment characteristics. A utility service 22 technician conducted a safety inspection of the gas appliances. In a few homes, the inspection 23 identified a minor issue that the technician resolved on the spot or during a follow-up visit, and 24 field measurements proceeded. During the second visit, the team completed equipment and 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 6
house characterization, conducted ventilation diagnostics, installed air quality measurement 1 equipment indoors and outdoors, and installed devices to track ventilation and gas cooking 2 appliance use. The participant was provided with an activity log for each day of the study and 3 asked to partake in normal household activities with the exception that windows and doors 4 should not be used for routine ventilation. Most homes were monitored for seven days, five were 5 sampled for 8 days and one for 6 days. On the third visit, all IAQ and mechanical equipment 6 monitoring devices were removed, the survey and activity logs were collected and a $350 gift 7 card to a home improvement store was provided to the participant. 8 Eligibility and Recruitment. The study was limited to owner-occupied, detached California 9 houses, built 2011 or later, with gas appliances, mechanical ventilation, and no smoking allowed. 10 Homes had to be customers of SoCalGas or PG&E. Homes with unusual filtration or ventilation 11 systems were excluded. Code compliance records obtained for 23 homes verified they were 12 certified to meet 2008 or more recent standards. The presence of compliant or close to compliant 13 mechanical ventilation equipment was verified in all homes ultimately included in the study. 14 Most participants were recruited through postcards (see SI) mailed to addresses identified on a 15 real estate website (Zillow.com), targeting single-family, detached homes built 2011 or later. 16 Some participants learned of the study via referrals. Details about the number of respondents, 17 early withdraws and non-qualifying homes is provided in the SI. 18

2.2. Field Data Collection Procedures 19
House and Equipment Characterization. The information collected about each home and its 20 mechanical equipment is summarized in the SI. 21
Air Leakage. Air leakage of the building envelope and the forced air heating/cooling system 22 were measured with the DeltaQ test (ASTM-E1554-2013, Method A) using a TEC Minneapolis 23 Blower Door System with DG-700 digital manometer (energyconservatory.com). The test 24 quantifies air leakage of the forced air system to outside of the living space under normal 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 7
operating conditions. Testing was conducted with software that automatically operated the 1 blower door fan through pressurization and depressurization, recorded airflow and pressure 2 differences, calculated envelope and duct leakage, and assessed if the measured parameters were 3 stable enough to provide both parameters. Air leakage was converted to air changes per hour at 4 50 Pa indoor-outdoor pressure difference (ACH50) using the estimated home volume. 5 Ventilation Airflows. Airflows of bath and laundry exhaust fans were measured using a TEC 6 Exhaust Fan Flow Meter (energyconservatory.com). Range hood airflows were measured using a 7 balanced-pressure flow hood method described by Walker and Wray9. A TEC Minneapolis Duct 8 Blaster, which is a calibrated, pressure-controlled, variable-speed fan, was connected to either 9 the exhaust inlet (preferred) or outlet. If connected at the inlet, a transition piece was adapted 10 onsite to cover the entire underside of the range hood or over-the-range microwave exhaust fan 11 (OTR). The flow through the Duct Blaster was adjusted to achieve neutral pressure between the 12 surrounding environment and the range hood inlet (or outlet) and airflow was determined from 13 the pre-calibrated fan speed versus airflow relationship. The measurement was repeated for the 14 lowest and highest settings and at least one medium setting if available. OTRs were tested in a 15 modified configuration: the top air inlet was covered with tape and the rate of air flowing into the 16 OTR was measured only at the bottom inlet. Subsequent testing at LBNL revealed that this 17 approach produces a biased measurement of total airflow occurring under the normal operating 18 configuration. Correction factors for most of the OTRs seen in the field were determined by 19 comparing the airflow into the bottom inlet when the top was taped to the total flow measured at 20 the exhaust duct outlet in laboratory experiments. The correction factors were applied to the field 21 measured airflows at each OTR setting. 22
Supply fan flow rates were not measured because the air inlets – usually on roofs or at the eave 23 level – could not be quickly and safely accessed by the field teams. It was also not feasible to 24 measure flows using in-duct velocity probes because the supply ducts were encased in spray 25 foam insulation in the attics. Supply airflows were inferred for two devices based on ratings. 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 8
Equipment Usage Monitoring. Operation of exhaust fans, range hoods, and clothes dryers were 1 determined using one of the following: motor on/off sensor (Onset HOBO UX90-004), vane 2 anemometer (Digisense WD-20250-22), or plug load logger (Onset HOBO UX120-018). The 3 field team chose an appropriate sensor for each fan configuration. Range hoods or OTRs were 4 monitored with anemometers and the velocity at each setting was determined at installation to 5 enable tracking of airflows for AER calculations. State sensors (Onset HOBO UX90-001) were 6 used to monitor the most often used exterior doors. Although participants were asked to keep 7 doors and windows closed during monitoring, it was deemed valuable to check for any extended 8 natural ventilation that could affect pollutant measurements and patio doors were assessed as 9 most likely to be left open. Cooktop and oven use were monitored using Maxim iButton 10 DS1922T temperature sensors. Burner use was inferred from analysis of the temperature signals. 11 Air Quality Measurements. Air quality parameters were measured outdoors on the premises 12 and at several locations indoors, as summarized in Table 1. The central indoor site was generally 13 in a large open room on the first floor that included the kitchen and/or living room, but monitors 14 were not placed directly in the kitchen. Performance specifications of air quality measurement 15 devices are provided in Table 1 with additional information in Table S1 of the SI. Table S2 16 provides a summary comparison of the methods used to collect air quality data in HENGH and 17 the CNHS. At the HENGH central indoor site, equipment was mounted on a stacked crate 18 system that allowed free airflow. The outdoor monitoring station was mounted on a tripod with 19 air sampling at roughly 2 m height and the station placed at least 3 m from any exterior wall or 20 pollutant source such as a grill. Outdoor formaldehyde and NOX passive samplers were placed 21 inside a 10 cm diameter PVC cap for rain protection. The ES-642 photometer is housed in a 22 weatherproof enclosure that incorporates a sharp-cut cyclone to exclude particles larger than 2.5 23 m aerodynamic diameter and an inlet heater to maintain a minimum relative humidity in the 24 incoming sample stream; it also auto-zeroes each hour. Monitors used to collect time-resolved air 25 quality data were purchased new at the start of the study and thus expected to perform according 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 9
to manufacturer specifications. Performance checks during the study are summarized below and 1 additional details are provided in the SI. 2
For the CO2 monitors, an initial visual check was conducted by operating all units together in the 3 warehouse used to prepare equipment for Northern California homes; but no formal calibration 4 was conducted at that time. In most homes, CO2 monitors were collocated during setup and 5 confirmed to read within 100 ppm of each other before deployment. Extech CO2 monitors were 6 checked against a calibrated PP Systems EGM-4 monitor during two collocation events at 7 LBNL, as described in the SI. Averaged over full spike-decay intervals, differences between 8 individual Extech units and the EGM-4 ranged from -20 ppm to 84 ppm. No corrections were 9 made to CO2 data and the possibility of larger deviations in some homes cannot be ruled out. 10 The ES-642 and BT-645 are aerosol photometers that translate light scattering measurements to 11 an estimated PM2.5 concentration based on a device-specific laboratory calibration using a 12 traceable reference of 0.6 m diameter polystyrene latex spheres. Since photometer response 13 varies with aerosol size distribution and optical properties, their accuracy for ambient (outdoor) 14 or indoor PM2.5 can vary substantially as the qualities of the aerosol vary10-14. The recommended 15 practice is to conduct a collocated gravimetric PM2.5 measurement and determine an environment 16 specific adjustment factor. In this study, we sought to check both the calibration factor and the 17 time-response of the Met One photometers by deploying Thermo pDR-1500 photometers with 18 onboard filter sampling indoors and outdoors at 8 homes. Due to power interruptions, valid 19 outdoor co-location data were obtained at only 5 homes and the results were too varied to 20 provide study-wide adjustment factors. To fill this gap, we obtained data from up to three 21 regulatory air quality monitoring stations closest to each house (Figure S1 of the SI) and 22 calculated outdoor PM2.5 for the study period at the house. As a second check on performance, at 23 most homes the indoor and outdoor photometers were operated side by side (typically outdoors) 24 for roughly an hour (Figure S2). Details about quality assurance for the air quality monitors are 25 provided in the SI. 26
IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 10
The standard software for the formaldehyde FM-801 monitor reports readings below 10 ppb as 1 “<LOD”. By special arrangement, GrayWolf provided modified software to enable us to access 2 device readings below this nominal detection limit, which we used in 25 homes. Prior research 3 indicates that the device may provide quantitative if more uncertain measurements below 10 4 ppb15. Some FM-801 formaldehyde was removed because of interference by high NO216 from 5 gas cooking burner use. Details about both adjustments are provided in the SI. 6 Duplicates and field blanks were collected to evaluate reliability for the passive samplers, and all 7 available duplicate samples were averaged to improve precision. Four Ogawa samplers prepared 8 according to manufacturer protocols were deployed at each home to measure NO2 and NOX: one 9 outdoors, two at the central indoor station (duplicates), and one field blank. The field blank was 10 opened either at the indoor or outdoor station, then packaged and stored in a refrigerator for the 11 monitoring week. At least four UMEx 100 formaldehyde samplers were deployed at each home: 12 one outdoors, two in the central indoor station (duplicates) and one in the bedroom. In most of 13 the sampled homes, a fifth sampler was opened indoors as a field blank, then immediately 14 packed and stored in a refrigerator during the monitoring week. The procedures used to analyze 15 passive samplers are summarized in the SI. The sampling rates for NO2 and NOX samples were 16 calculated based on measured average temperature and humidity according to Ogawa protocols. 17 For UMEx samplers we used the sampling rate of 20.4 mL/min recommended by the 18 manufacturer for air velocities <300 cm/min and 1 to 7 days of sampling. Offermann and 19 Hodgson have shown that sampling rates for the UMEx and other passive monitors start to drop 20 sharply when air velocity falls below about 75 cm/min17. Presenting measurements from six 21 occupied houses and one unoccupied research house, Matthews et al.18 reported that such low air 22 velocities were infrequent. Since we did not measure velocities around the passive samplers and 23 did not verify measured concentrations with pumped samples, it is possible that sampling rates 24 could have been lower than the assumed standard values at some times in some homes. 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 11
Survey and Activity Log. Participants were asked to complete a survey about the household 1 occupants and their general activities that impact ventilation and IAQ and also to complete an 2 activity log for each day of monitoring. The survey was a condensed version of the online survey 3 used to collect data about California detached homes built since 2002. Recruitment for the online 4 survey was conducted primarily through emails sent by SoCalGas to customers who lived in 5 homes that use natural gas and were thought to meet the requirement of being constructed in 6 2002 or later. A summary of findings from the survey is provided in the HENGH final project 7 report6. The abridged survey tool used for the field study and the daily activity log are included 8 in the SI to this paper. 9
Calculated Outdoor Air Exchange Rate (AER). The rate of outdoor air exchange – including 10 both mechanical ventilation and air infiltration – was calculated minute-by-minute in each home 11 following the Enhanced Model described in the 2017 ASHRAE Handbook– Fundamentals, as 12 summarized in the SI. The calculation assumed that windows and doors were closed throughout 13 the monitoring week (as required), so natural ventilation was negligible. The AER over the full 14 monitoring period in each home was calculated as the harmonic mean of the minute-by-minute 15 estimates. Measured AERs in CNHS houses2 that did not have mechanical ventilation and did 16 not open windows were analyzed to assess the accuracy of the infiltration portion of the AER 17 calculation, as described in the SI. 18

3. Results and Discussion 19

3.1. Locations and Seasons of Home Visits 20
The field study collected data from 48 homes in the San Francisco Bay Area and Central Valley 21 regions and 22 homes in Southern California, as shown in Figure 1. The breakdown by gas utility 22 service territory, California climate zone, and city is provided in Table S3. Sampling occurred 23 throughout the year, with slightly more homes visited in the months corresponding to summer 24 seasonal conditions (June–September, n=27 homes) than each of the other seasons, in which 13 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 12
to 16 homes were studied (Table S4). None of the homes were within 300 m of a freeway, 1 highway, or high-volume arterial road. 2

3.2. House and Household Characteristics 3
Characteristics of HENGH homes with selected comparisons to the CNHS and California data 4 from the 2017 American Housing Study (AHS) are reported in SI Tables S5–S15 and Table 2. 5 HENGH and CNHS samples had similar distributions of home size and occupant density; but 6 HENGH homes were newer when tested and more commonly had gas cooking appliances (Table 7 2). HENGH included one 2.5-story, 42 two-story, and 27 one-story houses (Table S8) and all but 8 one had an attached garage. HENGH homes mostly had three (n=20), four (n=28) or five (n=17) 9 bedrooms and almost all had multiple bathrooms (Tables S9–S10). Thirty-two HENGH homes 10 had vented gas fireplaces (Table S11). 11
HENGH households were similar in size to the AHS, with slightly more having 1-2 occupants 12 (46% vs. 41%), fewer with 3-4 occupants (34% vs. 42%) and similar 5+ occupants (17% vs. 13 15%) (Table S12). HENGH households had similar age demographics as the AHS, with 40% of 14 each having at least one resident under age 18 and 26-28% with at least one resident aged 65 or 15 older (Table S13). Relative to the AHS, the HENGH sample was skewed in terms of income and 16 education. In HENGH, 88% of the 66 participants who provided the information had a household 17 income of $100,000 or greater; in the AHS sample, only 60% reported such income (Table S14). 18 Of the 67 HENGH heads of household that reported education level, 88% had a college degree 19 and 54% had a graduate or professional degree; in the AHS, 56% had someone with a college 20 degree and 26% had someone with a graduate or professional degree (Table S15). 21 With the important caveat that the CNHS asked about medically diagnosed conditions and 22 HENGH asked simply about the conditions, HENGH households more commonly reported 23 someone with allergies (56% vs. 36%) or asthma (26% vs. 16%); CNHS also reported chemical 24 sensitivity in 3.7% of homes (HENGH survey did not ask about this condition). 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 13

3.3. Envelope Air Tightness 1
The distribution of measured envelope air tightness, expressed as the air changes per hour at a 50 2 Pascal indoor-outdoor pressure difference (ACH50), are shown in Figure S3. The mean, median, 3 and 10th–90th range of envelope air tightness from depressurization tests were 4.6, 4.4, and 3.4–4

6.0 ACH50. Measured air leakage under pressurization was higher than depressurization by 20% 5 on average due to “valving” of some air leakage pathways, e.g., from exhaust fan backdraft 6 dampers being pushed open during pressurization. Only four homes had envelope leakage less 7 than 3 ACH50, the level required for compliance with the 2018 International Energy 8 Conservation Code. Overall, HENGH homes had air leakage values similar to California homes 9 built in the early 2000s, as reported in the online residential diagnostics database 10 (resdb.lbl.gov)19 and in the CNHS, which had a mean ACH50 of 4.8. 11

3.4. Ventilation and Filtration Equipment 12
All 70 HENGH homes had ventilation equipment that was mostly or completely compliant with 13 the statewide standards. As summarized in Table S16, dwelling unit ventilation was provided by 14 an exhaust system in 64 homes and by a supply system in 6 homes. Fifty-five of the exhaust 15 systems used a continuous fan and 43 of those exhausted air from the laundry room; the others 16 exhausted from a bathroom. Three of the exhaust systems had remote fans located in the attic 17 and the others were upgraded laundry or bath exhaust fans. All supply systems were integrated 18 into the central forced air heating and cooling system; four had inline fans and two relied on the 19 central system fan operating on a timer to pull in outdoor air through a duct connecting the return 20 to the outdoors. In all but two of the homes with measured airflow, the flow exceeded the code 21 minimum requirement. The mean minimum requirement was 107 m3 h-1 and the mean installed 22 flow was 163 m3 h-1, about 50% higher. In many homes, the “extra” airflow could be explained 23 by use of a common fan size set to maximum capacity, i.e., not adjusted down to meet minimum 24 requirements. Very importantly, the general ventilation equipment was running in only 26% of 25 homes (18/70) when the field researcher(s) arrived for the initial visit. Systems with easily 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 14
understandable signage at the power switch for the system were much more likely to be 1 operating (see Table S17). 2
All of the homes had exhaust fans in the kitchen and in each bathroom, as required by the 3 standards. Kitchen ventilation was provided by a range hood in 32 homes and an over the range 4 (OTR) microwave in 38 homes. Twenty-two (69%) of the range hoods moved the required 50 L 5 s-1 or 100 cfm on the lowest speed setting, seven met the standard on a medium setting, and three 6 did so only at the highest setting. Of the 38 OTRs for which airflows were measured in homes, 7 method correction factors were obtained and applied to 22 devices. For this group, the estimated 8 airflow met the code requirement for 8 installed units (36%) on the lowest setting, 14 (64%) on a 9 medium or higher setting, and 20 (91%) on high or boost setting. The setting needed to produce 10 the required airflow is important because the code also requires that the fan operate at a sound 11 level of 3 sone or less, with the rationale that kitchen exhaust may not be used as needed if it is 12 too loud. Over 85% of the full bathrooms had exhaust fans that met the requirement of 25 L s-1 13 or 50 cfm, as shown in Figure S4. Exhaust fans in the toilet room or shower of the master 14 bathroom suite are not required to meet the airflow standard if the main exhaust fan in the 15 bathroom suite does so. These fans had lower measured airflows and only 60% met the 25 L s-1 16 benchmark. The median exhaust flows were 41, 37 and 31 L s-1 (87, 78 and 65 cfm) for master 17 bath, other bathroom and toilet/shower compartments. 18 Of the 69 homes with a forced air thermal conditioning system, 22 had only one filter, 34 had 19 two filters, 10 had three filters and 3 had four or more filters (with one filter per return duct). As 20 shown in Table S18, 96% (107/111) of the filters for which a performance rating could be 21 determined were MERV8 or better and 30% (33/111) were MERV11 or better. In the CNHS, 22 filter ratings were determined in 97 of the 108 homes: 49% (48) had MERV8 or better and 32% 23 (31) had MERV11 or better. In HENGH homes, we were able to determine the last date of 24 change for 85 filters: 58% (49) had been changed within the last 6 months, 22% (19) had not 25 been changed in the past year and 11 of those had never been changed (Table S19). Table S20 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 15
shows that 20 homes had filters that were clean or like new, 29 homes had filters that appeared 1 used or somewhat loaded, and 18 homes had at least one very dirty filter. There were a few 2 homes in which, at the owner’s request, the research team replaced (n=2) or installed (n=1) air 3 filters in the forced air systems during the first or second field visit, prior to monitoring. 4

3.5. Ventilation During the Week of Monitoring 5
Field teams set dwelling unit mechanical ventilation systems to operate during the monitoring 6 period in each home. The two homes with supply ventilation powered by their central thermal 7 conditioning system fans were ventilated during the study by running their laundry exhaust fans 8 continuously. The average air exchange rate (AER) resulting from infiltration and mechanical 9 equipment operating during the monitoring week was estimated for 63 homes, with results 10 provided in Figure S5. AER was not estimated for four homes with supply ventilation fans 11 because the system airflow could not be measured and for three homes that did not have a valid 12 envelope air leakage measurement, which is needed to calculate infiltration. Five homes that had 13 their dwelling unit exhaust fans stopped (presumably turned off by occupants) during the week 14 had low calculated AERs: 0.07–0.15 h-1. A sixth home, which had an intermittent exhaust fan 15 that was not programmed to provide sufficient ventilation (by error of the field team), also had a 16 low AER, of 0.06 h-1. For the 57 homes that had measured airtightness and mechanical 17 ventilation system airflows and their systems operated throughout the week of monitoring, the 18 mean, median and 10th–90th percentiles of the estimated infiltration + mechanical AERs were 19

0.33, 0.30, and 0.20–0.46 h-1. Mechanical ventilation provided substantially higher outdoor air 20 exchange rates than would have occurred by infiltration only, as shown in Figure S6. 21 The AERs estimated for HENGH homes operating with code-compliant systems and windows 22 presumed closed were marginally higher than in the CNHS (before ventilation was required), 23 which reported sample median AERs of 0.26 h-1 for 107 homes measured during a single 24 monitoring day and 0.24 h-1 for 21 homes measured over a 2-week period that included window 25 use. Twenty-two CNHS homes had mechanical equipment to provide dwelling unit ventilation; 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 16
these included 8 with heat recovery ventilators (HRV) and 14 with ducts connecting the forced 1 air heating/cooling system return duct to the outdoors. Of the 14 with outdoor air ducts, only 4 2 had controllers to operate the FAU for mechanical ventilation when no heating or cooling was 3 needed. During the day of CNHS monitoring, all of the HRVs but only 34% of the outdoor-4 connected FAU systems met the ASHRAE 62.2-2004 standard applicable at the time. 5 In several of the HENGH study homes, the actual outdoor air exchange over the week was likely 6 higher than the calculated values owing to use of natural ventilation. In six homes, the occupants 7 reported opening the house-to-patio and/or garage door(s) for more than 3 h per day on average. 8 The calculated AERs also could be roughly 20% higher based on the potential bias in infiltration 9 calculation indicated by the analysis of CNHS data from homes without mechanical ventilation. 10

3.6. Sources of Air Pollutants Reported in the General Survey 11 Almost all HENGH homes reported being completely smoke free; one reported that smoking 12 occurred a few times per year and one acknowledged informally that a family member smoked 13 daily in a bedroom, with the window open. Occasional candle burning was fairly common, with 14 16 HENGH participants reporting candle use a few times per month, 11 using a few times per 15 week, and 5 every day (Table S21). Thirty-four households had at least one furry pet and twelve 16 reported two or more; 20 reported no pets and 16 did not respond to the pet question (Table S22). 17

3.7. Occupancy and Activities During the Week of Monitoring 18 Data from the HENGH daily activity logs are provided for occupancy (Tables S23–S24) and 19 cooking (Tables S25–S27). Most of the homes had one to three occupants at home at any given 20 time when occupied and 88% of those reporting were occupied during time intervals totaling 16 21 or more hours per day on average. Thirty-four of 68 homes with daily log data reported using the 22 cooktop at least 7–14 times per week; oven use was less common. Cooktop use events were <30 23 min on average in most homes. Oven use was typically longer. Cooking and other activities 24 reported in the CNHS homes are provided in Table S28. 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 17

3.8. Air Pollutant Concentrations: Formaldehyde 1
Multiple measurements of formaldehyde in each HENGH home indicated very good sampling 2 precision and mostly similar concentrations in the master bedroom and central indoor sampling 3 location. The average mass on field blanks corresponded to 0.6 ppb for a 7-day collection period 4 and the 66 paired indoor samples agreed to within 1.0 ppb on average (median = 0.7 ppb). 5 Sample-period averaged concentrations calculated from half-hourly resolved GrayWolf (Shinyei) 6 multimode monitor data agreed well with the time-integrated sampler results as summarized in 7 Table S29 of the SI. Figure 2 presents the formaldehyde concentrations measured in the master 8 bedrooms and central indoor locations of each home by UMEx passive sampler. Among the 66 9 homes with valid samples in both locations, formaldehyde in the bedroom was >10% higher than 10 in the living room in 20 homes and less than 90% in 7 homes. The median and 10th–90th ratios of 11 bedroom to living room concentrations were 1.02 and 0.90–1.27. Period-averaged formaldehyde 12 determined by the multimode monitor indicated a similar trend of the master bedroom having 13 higher concentrations than the central area more frequently than the opposite. And the overnight 14 concentration in the bedroom was even higher than the period-average at that location. (See SI 15 for details). These findings suggest that for many people exposure to formaldehyde at home may 16 be higher than indicated by average concentrations at a central indoor site. 17 Figure 3 shows that homes built in 2011–2017 and mostly operating with mechanical ventilation 18 (HENGH) had formaldehyde concentrations substantially lower than those built in 2002-2005 19 and mostly not using mechanical ventilation (CNHS). Mean and median formaldehyde levels in 20 HENGH homes were 44% and 38% lower than in CNHS (Table 3). Differences between the 21 HENGH and CNHS indoor formaldehyde concentrations were found to be significant based on a 22 two-tailed Student’s t-test with equal variance comparing log-transformed concentrations (p-23 value = 3.4e-8) and the nonparametric Mann-Whitney test (p-value = 1.5e-7). The highest 24 formaldehyde measured in any home in the current study was 44 ppb while 28% of the CNHS 25 homes had a formaldehyde concentration over 44 ppb. Indoor emissions were the primary source 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 18
in both studies; but based on median indoor and outdoor values, the fraction contributed by 1 outdoor air increased from 6% in the mid-2000s to 15% more recently. 2 Formaldehyde levels in HENGH homes were all well below the World Health Organization 3 (WHO) indoor air guideline of 80 ppb and also below non-U.S. national guideline levels as 4 summarized by Salthammer 20. However, all homes were still above the 7 ppb (9 g/m3) Chronic 5 Reference Exposure Level set by the California Office of Environmental Health Hazard 6 Assessment, which is the applicable target in California. 7 The substantial reduction in formaldehyde compared to the CNHS a decade earlier appears to 8 result both from fewer homes being severely under-ventilated and from lower emissions. For 32 9 CNHS homes with measured air exchange rates below 0.2 h-1, mean and median formaldehyde 10 concentrations were 57 and 45 ppb. By contrast, in the HENGH dataset, only eight of the 63 11 homes for which overall AER was estimated had outdoor AERs below 0.2 h-1; and the mean and 12 median formaldehyde concentrations for these homes were 25 and 23 ppb. 13 Formaldehyde emission rates were calculated for 61 HENGH homes using the measured 14 concentrations and estimated AERs. The median and mean emission rates were 5.8 and 6.1 15 g/m3-h compared to median and mean values of 11 and 13 g/m3-h calculated from 99 homes 16 with the required component data in CNHS (Table 45 of Offermann et al., 2009). CNHS homes 17 had more varied formaldehyde emission rates, with a 10th to 90th percentile range of 4.0 to 23 18 g/m3-h whereas the range for HENGH homes was 2.8 to 8.3 g/m3-h. For this comparison, it is 19 important to note that the CNHS measured AERs with a PFT tracer gas whereas the HENGH 20 AERs were estimated by combining the measured mechanical ventilation airflows and calculated 21 air infiltration assuming no contributions from open windows or door. To the extent that actual 22 AERs in HENGH homes were higher than calculated – e.g. from a possible ~20% bias in the 23 calculated air exchange rates as discussed in the SI, or from use of windows and doors – the 24 formaldehyde emission rates in HENGH homes would have been higher than stated above. 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 19

3.9. Air Pollutant Concentrations: Fine Particulate Matter (PM2.5) 1 Time-resolved PM2.5 concentrations reported by indoor photometers were adjusted based on 2 comparison to gravimetric analysis of filter samples collected in 8 homes (Table S30). Indoor 3 photometer measurements were adjusted by a multiplier of 1.23 for the BT-645, and 0.90 for the 4 pDR-1500. Aside from the gravimetric adjustment, pDR-1500 also measured time-resolved 5 PM2.5 for comparison with BT-645. Hourly indoor readings from the 8 homes collected by the 6 two photometers were highly correlated (R2 = 0.96-0.99) and, after applying the respective 7 multipliers, agreed to within 1 g/m3 for 84% of the hourly readings, and 2 g/m3 for 96% of 8 the hourly readings. 9
Distributions of indoor PM2.5 in HENGH and CNHS are shown in Figure 4. Mean and median 10 indoor PM2.5 concentrations in HENGH were 44% and 54% lower than in CNHS homes (Table 11 3). Even with uncertainty in the photometer adjustment factors, these data indicate substantially 12 lower indoor PM2.5 in the more recently constructed homes. The difference in log-transformed 13 indoor PM2.5 concentrations measured by the two studies are statistically significant using 14 Student’s t-test (p-value = 2e-6) and nonparametric Mann-Whitney test (p-value = 2e-5). 15 Since outdoor air is a major source of PM2.5 inside U.S. homes21-25, it is important to consider if 16 the observed difference could be entirely attributed to lower PM2.5 outdoors during HENGH. The 17 CNHS reported 11 samples of outdoor PM2.5; based on the clustering sampling approach used in 18 that study, those measurements represent 28 homes. For the HENGH study, the 5 weeks of 19 collocated outdoor photometer and gravimetric samples had such varied ratios (see Table S30 of 20 SI) that they could not be used to adjust all of the outdoor photometer data. Data from regulatory 21 ambient air monitoring stations nearby to HENGH homes provide a second set of estimates of 22 areawide outdoor PM2.5 during the study. Table S31 and Figure S7 of the SI show that outdoor 23 PM2.5 estimates from the air monitoring stations are higher than those from unadjusted outdoor 24 photometer data. This is directionally consistent with outdoor photometer reading lower than the 25 indoor photometer in side-by-side monitoring and suggests that the outdoor photometer may be 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 20
understating the outdoor PM2.5. Summary statistics of outdoor PM2.5 from both data sets applied 1 for the HENGH study are compared to CNHS data in Table 3. While limitations of both data sets 2 make the comparison uncertain, the results in Table 3 do not indicate substantially lower PM2.5 3 outside of HENGH versus CNHS homes. The lower PM2.5 inside HENGH homes can therefore 4 not be attributed to lower outdoor PM2.5. 5
The lower indoor PM2.5 in HENGH homes could result from reduced penetration of particles 6 during air infiltration, lower indoor emissions (from cooking, candles, cleaning, etc.), more 7 effective kitchen ventilation, and/or improved filtration. Reduced particle entry during air 8 infiltration is not likely a major factor as the envelope air tightness was very similar in the two 9 samples and the higher median outdoor air exchange rates in the HENGH study would tend to 10 slightly increase indoor concentrations of outdoor particles as higher AERs bring in outdoor air 11 more quickly and leave less time for particles to deposit onto indoor surfaces. 12 Assessing the impact of filtration overall requires consideration of filter quality, airflow and 13 operating cycles of the central forced air system, and use of portable air filtration units. While the 14 full analysis is beyond the scope of this paper, it was reported above that HENGH homes more 15 commonly had at least a medium performance (MERV8) filter compared to CNHS homes. There 16 also may have been more portable air cleaner use in HENGH homes. Of the 64 HENGH 17 participants who answered the question, 14 (22%) reported using a standalone air cleaner. Air 18 cleaner use was self-reported in 17% of CNHS homes and 15% of respondents to the statewide 19 survey in 2002-41. 20
While it is difficult to compare the impact of all particle emitting activities – since emissions 21 vary so widely even for a defined activity – we can at least compare the frequency of cooking 22 and range hood use. In the CNHS study, during the day of IAQ monitoring, 87 homes (81%) 23 reported at least one use of the cooktop or oven and 81 (75%) reported at least one cooking event 24 involving frying, sautéing, baking or broiling. Despite this relatively high frequency of cooking 25 that can emit substantial quantities of PM2.5, only 22% of the CNHS occupant activity logs 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 21
reported any range hood use during the day of IAQ measurements and 44% reported some range 1 hood use during the prior week. Over the roughly one-week monitoring in HENGH homes, 34 of 2 the 68 submitted activity logs (50%) reported cooking with the cooktop or oven at least 7 or 3 more times during the week, i.e. once per day on average. The HENGH activity log did not ask 4 about the type of cooking. In the general survey responses, 50% of HENGH participants reported 5 using their range hood “most of the time” (4 of 5 times) or more and another 23% reported using 6 the range hood “sometimes” (2–3 out of 5 times). Initial analysis of cooktop temperature and 7 range hood/OTR use data indicate that kitchen ventilation was employed in some capacity during 8 roughly 29% of cooktop uses and 22% of oven uses and actual use during the monitored week 9 was much less than usage reported by survey. The range hood was operated for most or all of the 10 duration of cooktop use during 8% of cooktop use events and 3% of oven use events. 11

3.10. Air Pollutant Concentrations: Nitrogen Dioxide and Nitric Oxide 12 Distributions of NO2 concentrations inside HENGH and CNHS homes are presented in Figure 5 13 and summary statistics are provided in Table 3. The distributions were not significantly different 14 based on the nonparametric Mann-Whitney test (p-value = 0.08) and the means of the log-15 transformed data were not statistically different using the Student’s t-test (p-value = 0.15). This 16 occurred despite all HENGH homes having natural gas cooktops (compared to just 2% of CNHS 17 homes) and outdoor NO2 being higher in HENGH. The higher median indoor NO2 in HENGH 18 may be misleading as the CNHS median was in the group of data set as half of the quantitation 19 limit and the outdoor median for CNHS was lower (though uncertain for the sample as NO2 was 20 sampled outside of only a subset of homes). Differences in NO2 between HENGH and CNHS 21 homes were much smaller than those reported for homes with gas versus electric cooking in a 22 recent study of mostly older and smaller California homes 5. The highest weekly averaged NO2 23 measured in a HENGH home was below the California annual average standard of 30 ppb and 24 less than half of the U.S. annual air quality standard of 53 ppb. Figure S8 shows that for NO, 25 indoor concentrations were almost always higher than outdoors, as indoor emissions added to the 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 22
NO coming from outdoors. For NO2, deposition indoors resulted in indoor concentrations being 1 lower than outdoors in many homes. 2

3.11. Air Pollutant Concentrations: Carbon Dioxide as Indicator of Adequate Ventilation 3 Overall, time-averaged CO2 levels measured in HENGH and CNHS homes were similar, as 4 presented in Table 3. The one substantive difference – at the 90th percentile – aligns with 5 mechanical ventilation systems in HENGH homes more consistently providing outdoor air to 6 dilute occupant emissions of CO2. 7
Within HENGH homes, CO2 concentrations varied spatially (Figure 6). The highest time-8 averaged concentrations were in the master bedroom and concentrations in other bedrooms were 9 higher than in the main indoor living space. 10
CO2 concentrations also varied in time, with the highest concentrations occurring overnight in 11 bedrooms. Figure 7 shows the distributions of average CO2 concentrations in each room, looking 12 only at data from midnight to 5 am, and SI Figure S9 presents overnight CO2 concentrations 13 measured in the main indoor location and master bedrooms of the same houses. These results 14 indicate that CO2 in HENGH bedrooms did not reach the levels that have been reported to affect 15 sleep or next day alertness26, 27. 16

3.12. Satisfaction and Discomfort with Indoor Environmental Conditions 17 Sixty-eight of the 70 HENGH study participants provided responses to survey questions about 18 their satisfaction with environmental conditions in the home. Responding to the question “To 19 what extent are you satisfied or dissatisfied with the indoor air quality in your home?”, 68% 20 (n=46) selected one of four levels indicating positive satisfaction, 24% (n=16) selected neutral, 21 and 9% (n=6) marked one of four levels indicating dissatisfaction. These results are very similar 22 to those obtained from 2765 respondents to the online survey of people living in California 23 homes built before ventilation standards were in place. That survey, conducted in 2014, was 24 open to occupants of California homes built since 2002; yet almost all respondents lived in 25 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 23
homes built before 2011 and located in the SoCalGas service territory of Southern California6. In 1 the online survey, 69% indicated positive satisfaction, 21% were neutral, and 10% indicated 2 dissatisfaction with their IAQ. Among 68 field study respondents, 51% were satisfied with the 3 air quality outside of their homes, 17% were neutral and 32% were dissatisfied. These totals are 4 also similar to the online survey, for which 47% were satisfied, 27% were neutral and 26% were 5 dissatisfied with their outdoor air. When asked “How would rate you rate your home in 6 protecting you from outdoor air pollution?” 62% of responding field study participants were 7 satisfied, 31% were neutral and 7% were dissatisfied. The CNHS did not report results for IAQ 8 satisfaction and the survey reported by Piazza asked about “acceptability” of indoor air quality, 9 rather than “satisfaction”, which is not directly translatable. 10 The survey of HENGH participants – both field study and online – also asked about the 11 frequency of specific environmental discomforts, offering options of “never”, “few times a 12 year”, “few times a month”, “few times a week”, and “every day”. The CNHS study asked 13 participants if they experienced discomfort during the preceding week. Table 4 shows that 14 specific discomfort conditions were generally similar in the two studies, with the exception that 15 21% of HENGH participants reported not enough air movement compared to 12% of CNHS 16 participants experiencing the air as “too stagnant” in the week prior. The robustness of that 17 difference is unclear as 18% of the survey respondents from homes built around the same time as 18 those in the CNHS also expressed frequent dissatisfaction with air movement. 19 Survey responses from the field study were analyzed to evaluate if environmental satisfaction 20 differed in homes that had MV systems operating or not operating when the research team first 21 arrived to study homes. Results provided in Tables S32 to S34 indicate no statistically significant 22 associations with satisfaction for air quality, seasonal temperature, or other environmental 23 conditions (air movement, dryness or dampness, musty odors). 24 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 24

3.13. Comparison to Other Studies of Ventilation and IAQ in Recent Construction Homes 1 There have been few large field studies examining the impact of mechanical ventilation on IAQ 2 in recently constructed homes. The study that most directly addressed this topic examined 62 3 homes built in 2010-2012 to an Austrian efficiency standard that included general mechanical 4 ventilation with heat recovery (MVHR) and 61 homes constructed during the same years using 5 normal building standards without mechanical ventilation28. The study measured IAQ parameters 6 roughly 3 months and 1 year after occupancy and used interviews to collect data about health 7 symptoms and perceptions of IAQ and comfort29. The efficient homes with MVHR had lower 8 concentrations of total volatile organic compounds (TVOC), formaldehyde, saturated acyclic 9 aliphatic aldehydes, CO2, and radon28. While there were not significant differences in self-10 reported overall health status or for most symptoms, occupants of the efficient, ventilated homes 11 rated their environmental quality higher by more frequently noting positive attributes (pleasant, 12 clean, fresh and fragrant) and less frequently perceiving negative attributes (stale, stuffy, 13 stagnant, bad smelling or smoky)29. 14
The effects of improving ventilation in existing airtight homes was reported by Lajoie et al.30 in a 15 study that added mechanical ventilation with heat or enthalpy recovery to 43 of 83 Quebec area 16 homes of asthmatic children that were verified to be under-ventilated. IAQ parameters and the 17 children’s respiratory health were monitored over two years. The homes with added mechanical 18 ventilation had several statistically significant and substantial (>25%) improvements including 19 higher outdoor air exchange and lower CO2, formaldehyde, styrene, limonene and mold spores; 20 but also had higher indoor NO2 and di(2-ethylhexyl) phthalate. 21 Several studies have reported on the installed performance of mechanical ventilation systems in 22 modern homes. A study of mechanical ventilation systems in 299 Dutch homes completed in 23 2006-2009 conducted visual inspections, measured ventilation rates per room and equipment 24 noise, and asked occupants their perceptions of their indoor air quality31. Issues identified in 25 many homes included ventilation rates below and noise levels above building code requirements, 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 25
blocked supply vents, and absence of required controls. Problems occurred during installations, 1 maintenance and operations. A study in Belgium32 conducted mechanical ventilation system 2 diagnostics and measured carbon dioxide, temperature and humidity levels in 39 standard 3 construction homes built in 2007-2008 with wet room exhaust ventilation and trickle vent 4 supplies (and mean air leakage of 3 ACH50), 23 similarly tight (2 ACH50) low-energy homes 5 with MVHR, and 16 passive houses (0.5 ACH50) with MVHR. Installed equipment in many of 6 the homes did not achieve the required airflows at any setting and occupants generally operated 7 the systems at lower settings, leading to large differences between actual and design airflows. 8 Humidity and CO2 measurements showed some differences between groups of homes but none 9 indicated substantial problems. In a study of 29 homes in the U.S. state of Washington, which 10 has required mechanical ventilation for many years, researchers reported that most had systems 11 that were set, or that could be set to comply with the standard33. In many of the homes the MV 12 systems were not operating according to design standards when researchers first arrived. A study 13 of mechanical ventilation systems installed in 21 homes in the U.S. state of Florida34, which did 14 not require such systems at the time, found that only 12 were capable of operating and actual 15 airflows generally were well below design targets. These two U.S. studies reported problems 16 with installation (disconnected duct, blocked vent, poorly hung ducts, inoperable outdoor air 17 exhaust duct damper, ERV/HRV system installed backward) and operations and maintenance 18 (fan turned off, dirty filters, controller set to inadequate runtime fraction). 19 Among the air pollutants measured in HENGH, the most direct comparisons to prior U.S. studies 20 can be made for formaldehyde. HENGH homes had substantially lower formaldehyde than a 21 sample of homes constructed in the late 2000s with low-VOC flooring and paints along with 22 mechanical ventilation; those homes had mean formaldehyde of 27 ppb (33 g m-3) at adjusted 23 conditions of 23ºC, 43% RH, and 2.25 years old35. In a study in the U.S. state of Arizona, 24 apartments that were renovated in 2011 with low-VOC materials and mechanical ventilation had 25 reported mean(SD) and median formaldehyde levels of 27(7) ppb and 26 ppb roughly 1 year 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 26
after renovations36. These levels represented a decrease from pre-retrofit formaldehyde of 39(11) 1 ppb and 38 ppb (ibid). The higher concentrations measured in these studies relative to HENGH 2 could result from sampling occurring only during daytime hours in the summer season, a time at 3 which emissions are expected to be higher than concentrations measured over full diurnal cycles 4 and varied seasons37. The lower concentrations in HENGH homes could also result in part from 5 lower emissions resulting from the California air toxic control measure. 6

3.14. Limitations 7
The samples of homes included in the HENGH and CNHS studies may not accurately represent 8 the population of recently constructed homes in the state now or in the mid-2000s. Relative to 9 the general population of new home owners, HENGH households were biased toward higher 10 income and higher education and potentially also toward higher interest in IAQ (since they 11 volunteered to participate in the study). The impact of these biases is not known. 12 Even within the homes studied, the air quality measured in both HENGH and CNHS may not 13 accurately reflect average conditions. In the HENGH study, IAQ was measured while homes 14 were operated without natural ventilation (i.e., with occupants agreeing to keep windows and 15 doors closed) and with mechanical ventilation systems set to operate. This mode likely does not 16 represent conditions in newer California homes throughout the year, especially since we found 17 that general ventilation systems were not operating in 74% of the homes studied. This was not an 18 issue for CNHS because occupants were asked to use natural ventilation as normal. For both 19 studies, the act of participating could have changed occupant activities that impact indoor air 20 quality. Since CNHS sampling occurred over a single 24 h period, occupant routines may have 21 been impacted by modified schedules to accommodate sampling equipment installation, removal 22 and diagnostics on subsequent days. The processes of completing surveys and activity logs and 23 having monitoring equipment in the homes could have impacted behaviors in both studies. 24 Between study differences in recruitment, sample design and measurement methods also may 25 have impacted the relative results in HENGH and CNHS. 26 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 27
For the HENGH study, ventilation rates were not directly measured as they were in the CNHS. 1 The ventilation estimated by combining calculated infiltration rates and measured mechanical 2 airflows in the HENGH study would be biased low in any homes with sustained opening of 3 doors and/or windows for natural ventilation. 4

4. Conclusions 5
Measurements were conducted in 70 single-family, detached homes constructed in 2011–2017 6 under California building standards that require mechanical ventilation and a separate regulation 7 that limits formaldehyde emissions from composite wood products. All homes had mechanical 8 ventilation equipment that was mostly or completely compliant with the requirements. With the 9 general mechanical systems operating and most homes not using any natural ventilation, indoor 10 air pollutant levels were generally lower than those measured in a prior study of otherwise 11 similar California homes built before the ventilation and material emission standards took effect. 12 The recently constructed homes had somewhat lower PM2.5, much lower formaldehyde, and 13 slightly higher NO2 despite having gas cooking burners whereas homes in the prior study had 14 electric cooking. IAQ satisfaction was also similar in the newer homes as compared to homes 15 built in years prior. These results indicate the success of standards that limit formaldehyde 16 emissions and require ventilation systems to maintain acceptable IAQ. 17 18 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 28
Table 1. Measured Air Quality Parameters1 1
Measurement
Device
Para-
meters
Accuracy1 Res. Sampling
Locations
Met One ES-642
Photometer
PM2.5 ± 5% traceable standard with

0.6 um PSL
1-min Outdoor
Met One BT-645
Photometer
1-min Indoor: central
Extech SD-800
Infrared
CO2,
T,
RH
±40 ppm <1000; ±5%
>1000ppm; 2
±0.8°C
±4% below 70%; 4% of reading
+ 1% for 70–90% range
1-min Indoor: central,
master BR, other BR
Ogawa Passive
Samplers
NO2 and
NOX
Field validation3: 7 d rel. dev.:
3±2% NO2 at 11-37 ppb; 4±3%
NOX at 16-85 ppb; 10±9%
(NOX-NO2) at 4-56 ppb
1-week Outdoor;
Indoor: central
Aeroqual 500 Series
Electrochemical
NO2 ± 0.02 ppm within 0 to 0.2 ppm
range
1-min Indoor: central
GrayWolf FM-801
(Shinyei Multimode)
HCHO ± 4 ppb <40 ppb,
± 10% of reading ≥40 ppb
30-min Indoor: central,
master BR
SKC UMEx-100
Passive
HCHO

± 25%, exceeds OSHA
requirements
1-week Outdoor; Indoor:
central, master BR
Onset HOBO
UX100-011
Onset HOBO U23
Pro v2
T, RH ±0.21°C from 0° to 50°C
±2.5% from 10% to 90%; up to
±3.5% at 25°C including
hysteresis
1-min Indoor: central
(UX100-011);
Outdoor (U23);

1 Based on manufacturer specifications unless noted otherwise. Table S1 in Supporting Information provides some 2 additional information. 2 Manufacturer indicates ± 40 ppm for CO2<1000 ppm; the cited value of ±50 ppm reflects 3 our group’s experience (unpublished) with the monitors. 3 Field validation in California reported by Singer et al.38 4 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 29
Table 2. Selected House and Occupancy Characteristics1 1 Parameter HENGH CNHS
Year Built2 2011-2017 2002-2005
Monitoring 07/2016–04/2018 08/2006–03/2007
Age at Testing3 91% 3 years 90% 4.3 years
Floor Area (m2)4
Mean
Median (10th–90th)

244
243 (146–339)

248
251 (160–339)
Density (m2/person)
Mean
Median (10th-90th)

88 77 (45–143)

90 80 (48–142)
Gas Cooking Burners
Cooktop / Oven

100% / 43%

2% / 27%
1Additional information in SI Tables S5-S15. 2Table S5. 3Table S6. 4Table S7. 5Others had electric cooking. 2 Table 3. Time-averaged pollutant concentrations in California homes built 2011-2017 (HENGH, 3 current study) and 2002-2005 (CNHS, Offermann, 2009). 4 Location HCHO (ppb) PM2.5 g/m3) NO2 (ppb) CO2 (ppm)
Statistic HENGH CNHS1 HENGH CNHS1 HENGH CNHS1 HENGH CNHS2 Indoor N=68 N=105 N=67 N=28 N=66 N=29 N=69 N=107
Mean 19.8 35.0 7.5 13.4 5.8 5.2 620 610
Median 18.2 29.3 4.8 10.5 4.5 1.6 608 564
10th–90th 13–28 11–70 1.6–16 6.0–31 1.1–12 1.4–12 481–770 405–890 Outdoor N=66 N=394 N=673 N=114 N=65 N=114 No data No data Mean 2.2 1.8 9.3, 10.5 7.9 5.4 2.1
Median 2.3 1.7 6.8, 9.7 8.7 3.6 1.5
10th–90th 1.4–3.1 0.6–2.8

2.7–18.1,

5.3–16.7

5.0–10 0.1–11 1.4–1.7
1 From CNHS “all-home” sample frame dataset. 2 From Table 39 of Offermann (2009). 3 The first set of outdoor 5 values are from unadjusted, on-site photometer measurements over the full monitoring period at each home; the 6 second set are from air quality monitoring stations nearby to the homes and use only the 24-h data from complete 7 days during each monitoring period. 4 The CNHS collected one outdoor sample per cluster of 2-3 homes in close 8 proximity. Outdoor formaldehyde collected at clusters for all 108 homes. Outdoor samples for PM2.5 and NO2 9 collected for clusters that included 28 homes total. 10 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 30
Table 4. Discomfort rates reported by participants in California homes built with code-required 1 mechanical ventilation (HENGH), recent online survey of homes mostly built before dwelling unit 2 ventilation was required, and field study of homes built before ventilation was required (CNHS). 3 Parameter HENGH field
study (n=68)1
HENGH online
survey (n=2271)1
CNHS2
Too hot Winter: 14%
Summer: 31%
Winter: 10%
Summer: 41%
19%
Too cold Winter: 29%
Summer: 4%
Winter: 20%
Summer: 9%
15%
Too dry 9% 11% 8%
Too damp (HENGH) / too humid
(CNHS)
1% 2% 2%
Too much air movement
(HENGH) / too drafty (CNHS)
1% 5% 0%
Too stagnant / not enough air
movement
21% 18% 12%
Too dusty Not asked Not asked 11%
Musty odor 1% 3% 13% in bathroom
1-3% other locations
1 When asked how often does the discomfort occurs, respondent selected “few times per week” or “daily”. 2 From 4 Table 44 of Offermann (2009), respondents reporting that the discomfort occurred during 3 weeks prior. For musty 5 odor, the CNHS asked if participants had “observed, seen or smelled mold” in the past week in various locations. 6 7 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 31
1 Figure 1. Locations of study homes. 2
3 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 32
1 Figure 2: One-week integrated formaldehyde measured with passive samples: Comparison of 2 concentrations in master bedroom and large, open common room (main) indoor locations 3 4 Figure 3: Time-Integrated formaldehyde concentrations measured in California homes built before 5 (CNHS) and after (HENGH) mechanical ventilation was required. 6

IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 33
1 Figure 4: Time-averaged PM2.5 concentrations measured in California homes built before (CNHS) 2 and after (HENGH) mechanical ventilation was required. 3 4 Figure 5: Time-integrated NO2 concentrations measured in California homes built before (CNHS) 5 and after (HENGH) mechanical ventilation was required. Most CNHS homes had electric cooking 6 and all HENGH homes had gas cooking burners. 7

IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 34
1 Figure 6: Time-average CO2 concentrations in indoor main living space and bedrooms. 2 3 Figure 7: Nighttime (midnight-5am) CO2 in indoor main living space and bedrooms 4 5 IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 35

5. References 1

1. Piazza T, Lee R, Sherman M, Price P. Study of Ventilation Practices and Household 2 Characteristics in New California Homes. Final Report for Energy Commission Contract 3 500-02-023 and ARB Contract 03-026. CEC-500-2007-033; Sacramento, CA: California 4 Energy Commission and California Air Resources Board; June 2007, 2007. 5

2. Offermann FJ. Ventilation and Indoor Air Quality in New Homes. CEC-500-2009-085; 6 Sacramento, CA: California Energy Commission and California Air Resources Board; 2009. 7

3. Lawrence Berkeley National Lab. LBNL. Ventilate Right: Ventilation Guide for New and 8 Existing California Homes. https://homes.lbl.gov/ventilate-right/ashrae-standard-622 Last 9 Accessed:05-Oct-2019- 10

4. Logue JM, Klepeis NE, Lobscheid AB, Singer BC. Pollutant Exposures from Natural Gas 11 Cooking Burners: A Simulation-Based Assessment for Southern California. Environ Health 12 Perspect. 2014;122:43-50. 13

5. Mullen NA, Li J, Russell ML, Spears M, Less BD, Singer BC. Results of the California 14 Healthy Homes Indoor Air Quality Study of 2011-2013: impact of natural gas appliances on 15 air pollutant concentrations. Indoor Air. 2016;26:231-45. 16

6. Chan WR, Kim Y-S, Less BD, Singer BC, Walker IS. Ventilation and Indoor Air Quality in 17 New California Homes with Gas Appliances and Mechanical Ventilation. LBNL-2001200; 18 Berkeley CA: Lawrence Berkeley National Laboratory; 2019. 19

7. California Air Resources Board. CARB. Composite Wood Products Airborne Toxic Control 20 Measure. www.arb.ca.gov/toxics/compwood/compwood.htm Last Accessed:05-Oct-2019- 21

8. Chan WR, Kim Y-S, Singer BC, Walker IS, Sherman MH. Healthy Efficient New Gas 22 Homes (HENGH) Field Study Protocol. LBNL-1005819; Berkeley, CA: Lawrence Berkeley 23 National Lab; 2016. 24

9. Walker IS, Wray CP, Dickerhoff DJ, Sherman MH. Evaluation of flow hood measurements 25 for residential register flows. LBNL-47382; Berkeley CA: Lawrence Berkeley National 26 Laboratory; 2001. 27

10. Dacunto PJ, Cheng KC, Acevedo-Bolton V, Jiang RT, Klepeis NE, Repace JL, Ott WR, 28 Hildemann LM. Real-time particle monitor calibration factors and PM2.5 emission factors 29 for multiple indoor sources. Environmental Science-Processes & Impacts. 2013;15:1511-30 1519. 31

11. Tryner J, Good N, Wilson A, Clark ML, Peel JL, Volckens J. Variation in gravimetric 32 correction factors for nephelometer-derived estimates of personal exposure to PM2.5. 33 Environ Pollut. 2019;250:251-261. 34

12. Singer BC, Delp WW. Response of consumer and research grade indoor air quality monitors 35 to residential sources of fine particles. Indoor Air. 2018;28:624-639. 36

13. Zhang J, Marto JP, Schwab JJ. Exploring the applicability and limitations of selected optical 37 scattering instruments for PM mass measurement. Atmos. Meas. Tech. 2018;11:2995-3005. 38

14. Wang XL, Chancellor G, Evenstad J, Farnsworth JE, Hase A, Olson GM, Sreenath A, 39 Agarwal JK. A Novel Optical Instrument for Estimating Size Segregated Aerosol Mass 40 Concentration in Real Time. Aerosol Sci Technol. 2009;43:939-950. 41

15. Carter EM, Jackson MC, Katz LE, Speitel GE. A coupled sensor-spectrophotometric device 42 for continuous measurement of formaldehyde in indoor environments. J Exposure Sci 43 Environ Epidemiol. 2014;24:305-310. 44
IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 36

16. Maruo YY, Yamada T, Nakamura J, Izumi K, Uchiyama M. Formaldehyde measurements in 1 residential indoor air using a developed sensor element in the Kanto area of Japan. Indoor 2 Air. 2010;20:486-493. 3

17. Offermann FJ, Hodgson AT. In Accurancy of Three Types of Formaldehyde Passive 4 Samplers, Indoor Air 2018, Philadelphia PA, 2018; International Society of Indoor Air 5 Quality Sciences: Philadelphia PA, 2018. 6

18. Matthews TG, Thompson CV, Wilson DL, Hawthorne AR, Mage D. Air velocities inside 7 domestic environments: An important parameter in the study of indoor air quality and 8 climate. Environ Int. 1989;15:545-550. 9

19. Chan WYR, Joh J, Sherman MH. Analysis of air leakage measurements of US houses. 10 Energ Buildings. 2013;66:616-625. 11

20. Salthammer T, Mentese S, Marutzky R. Formaldehyde in the Indoor Environment. Chem 12 Rev. 2010;110:2536-2572. 13

21. Allen RW, Adar SD, Avol E, Cohen M, Curl CL, Larson T, Liu LJS, Sheppard L, Kaufman 14 JD. Modeling the Residential Infiltration of Outdoor PM2.5 in the Multi-Ethnic Study of 15 Atherosclerosis and Air Pollution (MESA Air). Environ Health Perspect. 2012;120:824-16 830. 17

22. Wallace LA, Mitchell H, O'Connor GT, Neas L, Lippmann M, Kattan M, Koenig J, Stout 18 JW, Vaughn BJ, Wallace D, Walter M, Adams K, Liu LJS. Particle concentrations in inner-19 city homes of children with asthma: The effect of smoking, cooking, and outdoor pollution. 20 Environ Health Perspect. 2003;111:1265-1272. 21

23. Allen R, Larson T, Sheppard L, Wallace L, Liu LJS. Use of real-time light scattering data to 22 estimate the contribution of infiltrated and indoor-generated particles to indoor air. Environ 23 Sci Technol. 2003;37:3484-3492. 24

24. Meng QY, Spector D, Colome S, Turpin B. Determinants of indoor and personal exposure 25 to PM2.5 of indoor and outdoor origin during the RIOPA study. Atmos Environ. 26 2009;43:5750-5758. 27

25. Rodes CE, Lawless PA, Thornburg JW, Williams RW, Croghan CW. DEARS particulate 28 matter relationships for personal, indoor, outdoor, and central site settings for a general 29 population. Atmos Environ. 2010;44:1386-1399. 30

26. Mishra AK, van Ruitenbeek AM, Loomans M, Kort HSM. Window/door opening-mediated 31 bedroom ventilation and its impact on sleep quality of healthy, young adults. Indoor Air. 32 2018;28:339-351. 33

27. Strom-Tejsen P, Zukowska D, Wargocki P, Wyon DP. The effects of bedroom air quality on 34 sleep and next-day performance. Indoor Air. 2016;26:679-686. 35

28. Wallner P, Munoz U, Tappler P, Wanka A, Kundi M, Shelton JF, Hutter HP. Indoor 36 Environmental Quality in Mechanically Ventilated, Energy-Efficient Buildings vs. 37 Conventional Buildings. Int J Environ Res Public Health. 2015;12:14132-14147. 38

29. Wallner P, Tappler P, Munoz U, Damberger B, Wanka A, Kundi M, Hutter HP. Health and 39 Wellbeing of Occupants in Highly Energy Efficient Buildings: A Field Study. Int J Environ 40 Res Public Health. 2017;14. 41

30. Lajoie P, Aubin D, Gingras V, Daigneault P, Ducharme F, Gauvin D, Fugler D, Leclerc JM, 42 Won D, Courteau M, Gingras S, Heroux ME, Yang W, Schleibinger H. The IVAIRE project 43 - a randomized controlled study of the impact of ventilation on indoor air quality and the 44 respiratory symptoms of asthmatic children in single family homes. Indoor Air. 45 2015;25:582-597. 46
IAQ in Mechanically Ventilated U.S. Homes INA-190-10-297-R2 04-April-2020 37

31. Balvers J, Bogers R, Jongeneel R, van Kamp I, Boerstra A, van Dijken F. Mechanical 1 ventilation in recently built Dutch homes: technical shortcomings, possibilities for 2 improvement, perceived indoor environment and health effects. Architectural Science 3 Review. 2012;55:4-14. 4

32. Laverge J, Delghust M, Janssens A. Carbon Dioxide Concentrations and Humidity Levels 5 Measured in Belgian Standard and Low Energy Dwellings with Common Ventilation 6 Strategies. International Journal of Ventilation. 2015;14:165-180. 7

33. Eklund K, Kunkle R, Banks A, Hales D. Pacific Northwest Residential Effectiveness Study - 8 FINAL REPORT NEEA Report #E15-015; Portland, OR: Prepared by Washington State 9 University Energy Program; 2015. 10

34. Sonne JK, Withers C, Vieira RK. Investigation of the effectiveness and failure rates of 11 whole-house mechanical ventilation systems in Florida. FSEC-CR-2002-15; Cocoa, FL: 12 June 1, 2015, 2015. 13

35. Hult EL, Willem H, Price PN, Hotchi T, Russell ML, Singer BC. Formaldehyde and 14 acetaldehyde exposure mitigation in US residences: in-home measurements of ventilation 15 control and source control. Indoor Air. 2015;25:523-535. 16

36. Frey SE, Destaillats H, Cohn S, Ahrentzen S, Fraser MP. The effects of an energy efficiency 17 retrofit on indoor air quality. Indoor Air. 2015;25:210-219. 18

37. Huangfu YB, Lima NM, O'Keeffe PT, Kirk WM, Lamb BK, Pressley SN, Lin BY, Cook 19 DJ, Walden V, Jobson BT. Diel variation of formaldehyde levels and other VOCs in homes 20 driven by temperature dependent infiltration and emission rates. Build Environ. 2019;159. 21

38. Singer BC, Hodgson AT, Hotchi T, Kim JJ. Passive measurement of nitrogen oxides to 22 assess traffic-related pollutant exposure for the East Bay Children's Respiratory Health 23 Study. Atmos Environ. 2004;38:393-403. 24
25 IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-1

SUPPORTING INFORMA TION
Indoor Air Quality in California Homes with Code-Required Mechanical Ventilation Brett C. Singer1, Wanyu R. Chan1, Yang-Seon Kim1,2, Francis J. Offermann3, Iain S. Walker1 1 Residential Buildings Systems Group and Indoor Environment Group, Lawrence Berkeley National Laboratory, Berkeley, California, USA
2 Wichita State University, Wichita, Kansas, USA
3 Indoor Environmental Engineering, San Francisco California, USA

Contents
CONTENTS ......................................................................................................................................................... 1 LIST OF FIGURES ................................................................................................................................................. 2 LIST OF TABLES ................................................................................................................................................... 2 METHODS .......................................................................................................................................................... 4 RECRUITMENT AND SCREENING ........................................................................................................................................ 4 INFORMATION COLLECTED FOR HOUSE AND EQUIPMENT CHARACTERIZATION ............................................................................ 4 SPECIFICATION OF AIR QUALITY MONITORING EQUIPMENT .................................................................................................... 5 LOCATIONS OF AMBIENT AIR QUALITY MONITORING STATIONS USED TO ESTIMATE OUTDOOR PM2.5 ........................................... 8 QUALITY ASSURANCE PROCEDURES FOR AIR QUALITY MONITORS ........................................................................................... 9 WEIGHING OF FILTERS FOR GRAVIMETRIC PM2.5 DETERMINATION ........................................................................................ 10 PASSIVE SAMPLER PROCEDURES AND QUALITY ASSURANCE ................................................................................................. 10 POTENTIAL IMPACT OF LOW AIR SPEEDS ON PASSIVE SAMPLER DATA .................................................................................... 12 ADJUSTMENTS TO FORMALDEHYDE DATA FROM FM-801 MONITOR ..................................................................................... 13 CALCULATION OF OUTDOOR AIR EXCHANGE RATE .............................................................................................................. 13 ESTIMATE OF POTENTIAL BIAS IN CALCULATED AIR INFILTRATION .......................................................................................... 14 RESULTS ............................................................................................................................................................ 16 HOUSE CHARACTERISTICS .............................................................................................................................................. 16 HOUSEHOLD DEMOGRAPHICS ......................................................................................................................................... 19 AIR TIGHTNESS ............................................................................................................................................................ 21 VENTILATION AND FILTRATION EQUIPMENT ...................................................................................................................... 22 GENERAL OCCUPANCY AND SOURCES – FROM SURVEY ....................................................................................................... 27 OCCUPANCY AND SOURCES DURING WEEK OF MONITORING ............................................................................................... 27 AIR POLLUTANT CONCENTRATIONS: FORMALDEHYDE .......................................................................................................... 30 AIR POLLUTANT CONCENTRATIONS: PM2.5 ....................................................................................................................... 31 ANALYSIS OF REGULATORY AIR MONITORING DATA TO ESTIMATE PM2.5 OUTSIDE OF HENGH HOMES ....................................... 31 AIR POLLUTANT CONCENTRATIONS: NITROGEN DIOXIDE AND NITRIC OXIDE ............................................................................ 34 AIR POLLUTANT CONCENTRATIONS: CO2 .......................................................................................................................... 35 IEQ SATISFACTION BY VENTILATION SYSTEM OPERATION .................................................................................................... 36 RECRUITMENT POSTCARD ................................................................................................................................. 38 DAILY ACTIVITY LOG .......................................................................................................................................... 39 OCCUPANT SURVEY........................................................................................................................................... 40 IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-2

List of Figures
Figure S1: Locations of PM2.5 air monitoring stations (blue) in relation to study homes (red). ... 8 Figure S2. Results of side-by-side deployment of indoor and outdoor MetOne photometers at each house, typically outdoors. ....................................................................................................... 9 Figure S3: Distribution of ACH50 from Envelope Leakage Measurements ................................ 21 Figure S4: Bathroom Exhaust Fan Measured Flow Rates ............................................................ 23 Figure S5: Total Estimated Air Exchange Rate ............................................................................ 25 Figure S6: Infiltration and Total Airflow (Mechanical + Infiltration) .......................................... 26 Figure S7. Comparison between mean outdoor PM2.5 measured using MetOne photometer and inverse distance weighted ambient monitoring data (N=67). ....................................................... 33 Figure S8: One-Week Integrated NO2, NO, and NOx Concentrations ........................................ 34 Figure S9: Overnight (midnight-5am) CO2 measurements in indoor main living space and master bedroom. ....................................................................................................................................... 35

List of Tables
Table S1. Specifications of air pollutant monitoring equipment .................................................... 5 Table S2. Comparison of study design and measurement methods HENGH and CNHS studies of indoor air quality and ventilation in single family detached homes ............................................... 6 Table S3. Sampled Homes by Cities and Climate Zones (N=70) ................................................ 16 Table S4. Sampled Homes by Seasons ......................................................................................... 16 Table S5. Sampled Homes by Year Built ..................................................................................... 17 Table S6. Age of Homes When Sampled1 .................................................................................... 17 Table S7: Sampled Homes by Floor Area .................................................................................... 17 Table S8: Sampled Homes by Number of Stories ........................................................................ 18 Table S9: Sampled Homes by Number of Bedrooms ................................................................... 18 Table S10: Sampled Homes by Number of Bathrooms ................................................................ 18 Table S11: Locations of Gas Fireplaces ....................................................................................... 19 Table S12: Number of Occupants in Sampled Homes ................................................................. 19 Table S13: Number of Occupants in Sampled Homes by Age Group ......................................... 20 Table S14: Total Household Income in Sampled Homes ............................................................. 20 Table S15: Education Level of Head of Household in Sampled Homes ...................................... 21 Table S16: Whole House Ventilation System Type ..................................................................... 22 Table S17: Whole House Ventilation System Control ................................................................. 22 Table S18: Air Filter MERV Ratings ........................................................................................... 23 Table S19: Time Since Last Air Filter Change ............................................................................. 24 Table S20: Condition of Air Filters Observed by Field Team ...................................................... 24 Table S21: How Frequently Are Candles Used in the Home ....................................................... 27 Table S22: Number of Furry Pets in Homes ................................................................................. 27 Table S23: Self-Reported Average Occupancy (Number of People) When Home Was Occupied ....................................................................................................................................................... 27 Table S24: Self-Reported Average Occupied Hours per Day During Monitoring Week ............ 28 IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-3
Table S25: Self-Reported Cooktop Use (Number of Times) During Monitoring Week .............. 28 Table S26: Self-Reported Oven and Outdoor Grill Use During Monitoring Week ..................... 28 Table S27: Average Cooking Activity Duration During One-Week Monitoring, Self-Reported 29 Table S28. CNHS Activities (Table 42 and 43 of Offermann et al. 2009): .................................. 29 Table S29: Comparison of Time-Integrated Formaldehyde Measured with Two Methods ......... 30 Table S30. Time-integrated PM2.5 concentrations measured by MetOne and Thermo pDR-1500 photometers compared with gravimetric analysis of co-located filter samples. ........................... 31 Table S31. Summary statistics (N=67) of the mean outdoor PM2.5 measured using MetOne photometer and inverse distance weighted ambient monitoring data. .......................................... 32 Table 32. Air quality satisfaction reported by participants. .......................................................... 36 Table 33. Satisfaction with seasonal temperature conditions by ventilation system status on first visit to home. ................................................................................................................................. 36 Table 34. Satisfaction with environmental parameters by ventilation system status on first visit to home. ............................................................................................................................................. 37

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-4
Methods
Recruitment and Screening
Most participants were recruited through postcards mailed to addresses identified on a real estate website (Zillow.com), targeting single-family, detached homes built 2011 or later. Some participants learned of the study via referrals. LBNL attempted to contact all who expressed interest through the study website or by telephone. On contact, participant eligibility was confirmed and participant responsibilities, including keeping windows closed, were described.

This process identified 103 eligible and interested candidates and led to monitoring in 72 homes.

Most of the other 31 candidates did not respond to three attempts to schedule visits or withdrew before the first scheduled visit. One consented participant withdrew between the first and second visits. Another was excluded when the field team found during the first visit that the home was built before 2011. These participants received a $75 gift card. Two monitored homes did not have compliant ventilation systems and are not included in the data reported herein.

Information Collected for House and Equipment Characterization  House information: floor area and ceiling heights; number of stories, bedrooms, full and half baths, and other rooms on each floor; attached garage, number of parking spots, etc.  Whole-house mechanical ventilation system. Noted basic design (exhaust, supply, or balanced); type of control; make, model and rated flow; and fan settings.  Other ventilation equipment: bath and toilet room exhaust fans, kitchen range hood, and any laundry exhaust fans. Noted make, model and rated flow, type of control for each fan; and for kitchen note if range hood is microwave or simple range hood.  Heating and cooling system(s). Noted type of system (all were forced air), make and model, capacity (in tons and Btuh) and whether system was zoned. Noted dimensions and location of each return and locations of filter(s) if not at the return air grille. Noted location(s) and types of thermostats. For each filter in a forced air heating or cooling system, recorded make, model and performance rating and visually assessed condition of filter; also took photo.

Identified and characterized thermostat and marked location on floor plan.  Attic. Noted whether it was vented or unvented and the type of insulation. Photographed ductwork, gas furnace, exhaust fans, and vents.
 Gas-burning appliances. Noted make, model and firing rates of all burners or photographed nameplate. Noted locations on floor plans.

Floor plans were generally obtained from builders’ websites; otherwise they were sketched on site. Photos were taken of the home exterior, garage, gas appliances, mechanical ventilation equipment, air filters, and any special features.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-5
Specification of Air Quality Monitoring Equipment
Table S1. Specifications of air pollutant monitoring equipment Parameter Device make and
model
Range and
Resolution
Accuracy in
Product Literature
Other
Temperature Onset HOBO
UX100-011
Range: -20° to 70°C.

Resolution: 0.024°C at
25°C
±0.21°C from 0° to
50°C

Response time: 4 min in
air moving 1 m/s
Drift: <0.1°C per year
Temperature Extech SD800 0 to 50°C ±0.8°C
Relative
humidity
Onset HOBO
UX100-011
Range: 1% to 95%
(non-condensing);
Resolution: 0.05%

±2.5% from 10% to
90%; up to ±3.5% at
25°C including
hysteresis
Response time: 11 sec to
90% in airflow of 1 m/s
Drift: <1% per year
typical
Relative
humidity
Extech SD800 Range: 10-90% ±4%RH below
70%; 4% of reading
+ 1% for 70–90%
range

Particulate
matter, PM2.5
MetOne ES-642
MetOne BT-645
Range: 0-100 mg/m3.

Resolution: 0.001
mg/m3.
± 5% traceable
standard with 0.6um
PSL

Carbon dioxide,
CO2
Extech SD800 Range: 0-4000 ppm;
Resolution: 1 ppm
±40 ppm under
1000 ppm; ±5%
>1000 ppma

Nitrogen
Dioxide
Aeroqual 500
Series
Range: 0 to 1 ppm ± 0.02 ppm within 0
to 0.2 ppm range

Formaldehyde GrayWolf
(Shinyei)
Multimode
Monitor
20 to 1000 ppb ± 4ppb for <40ppb,
± 10% of reading
for ≥40ppb
30 min resolution; 20
ppb is lowest reliable
value with stated
accuracy
a Extech monitors did not achieve this performance when compared to a calibrated PPSystems EGM-4 in an injection-decay experiment in a small, room-sized chamber during monitoring as described in the text.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-6
Table S2. Comparison of study design and measurement methods HENGH and CNHS studies of indoor air quality and ventilation in single family detached homes Parameter HENGH CNHS
Number of Homes 70 108
Year Built
(Monitoring)
2011-2017
(Jul 2016 – Apr 2018)
2002-2005
(Aug 2006 – March 2007)
Dwelling Unit
Mechanical
Ventilation
(Operational
Systems)
All 70 homes had systems that met
2008 or later California code:
64 exhaust; 6 supply.

13 homes had systems that met
ASHRAE 62.2-2004:
8 balanced (HRV); 5 with duct
connecting FAU to outdoors and
controller for ventilation.
9 homes had duct connecting FAU
to outdoors but no controller for
ventilation.

Gas Cooking
Appliances
Cooktops: 100%
Ovens 43%
Cooktops: 2%
Ovens: 27%
Natural
Ventilation
Occupants agreed to not use
windows for ventilation.

Occupants asked to use windows
as they do normally.

Duration ~7 days ~24 hour
Locations for IAQ
parameter
measurements
• Living, dining or family room:

PM2.5, CO2, NOX, NO2,
formaldehyde.
• Master bedroom: CO2 and
formaldehyde.
• Other bedroom(s): CO2
• Outside: PM2.5, NOX, NO2,
formaldehyde.
• Living, dining or family room:

VOCs, CO2, CO, formaldehyde in
all homes; PM2.5 in 28 homes; NO2
in 29 homes.
• Outside: formaldehyde at each
cluster of 2-3 homes (n=39); PM2.5
and NO2 at 11 clusters.

Air Contaminant
Measurement
Methods
• Formaldehyde, NO2, NOX: time-
integrated passive samplers.
• Formaldehyde: colorimetric
sensor/photometer, 30-min logs
• PM2.5: Estimated by photometry
with indoor adjusted using time-
integrated filter samples.
• CO2: Passive, NDIR, 1-min
• Formaldehyde, NO2, 10 VOCs:
time-integrated, pumped samples
• PM2.5: time-integrated pumped
filter samples with size selective
inlets and gravimetric analyses.
• CO2: Passive, NDIR, 1-min
• CO: Passive, Electrochemical, 1-
min
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-7
Parameter HENGH CNHS
• T: thermistor sensor
• RH: Thin film capacitive sensor
• T: thermistor sensor
• RH: Thin film capacitive sensor
Air Contaminant
Measurement
QA/QC
• Formaldehyde, NOX, NO2:
duplicates, field blanks,
manufacturer’s recommended
sampling rate.
• PM2.5: zero at sample start, span
adjustment calculated from
simultaneous gravimetric samples
at 8 indoor locations.
• CO2: baseline and span checks at
middle of study. No adjustment of
field data.
• NO2: baseline and span checks
prior to sampling in most homes.
• T and RH sensors used factory
calibration with no field
calibrations.
• Formaldehyde, PM2.5, NO2, 10
VOCs: duplicates, field blanks,
sampling rate measurements at
start and stop.
• CO2 and CO: zero and span
calibration at start and stop of
sampling at each home and
corresponding adjustment of field
data.
• T and RH sensor calibration prior
to field session and corresponding
adjustment of field data.

Record of natural
ventilation use.

Participant affirmed that windows
would not be used for ventilation,
per study requirements. Loggers on
two most-used doors. No loggers
or signage on windows. Daily log
asked for hours that any windows
were opened but not the amount
opened.

Occupants instructed to operate
windows normally. Loggers on
windows that occupants reported to
use most frequently, and signage
with logs on all windows for
occupants to record hours and
amount opened.

Method to
measure or
estimate outdoor
air ventilation rate
Estimated from measured
mechanical airflows and modeled
infiltration with unbalanced
ventilation.

Measured with perfluorocarbon
tracer (PFT) gas.

Abbreviations: HRV = Heat recovery ventilator; FAU = forced air unit; NDIR = non-disperse infrared.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-8

Locations of Ambient Air Quality Monitoring Stations Used to Estimate Outdoor PM2.5  San Francisco Bay Area

 Sacramento and Central Valley
Southern California 

Figure S1: Locations of PM2.5 air monitoring stations (blue) in relation to study homes (red).

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-9
Quality Assurance Procedures for Air Quality Monitors
The indoor and outdoor PM2.5 monitors were co-located for roughly one hour during the instrument deployment visit at each home. In most cases the co-location was outdoors at the location of the outdoor monitor. Co-located comparisons were available from 45 homes. In two of the homes, the two monitors measured very different concentrations likely because the outdoor monitor had a heated inlet that was set to activate when relative humidity reached above 60%, and the indoor monitor did not. The heated inlet prevents condensation that could damage the instrument. The indoor monitor did not have a heated inlet because high humidity is generally not a concern when sampling indoors. At the two homes during the one-hour co- location test, the outdoor monitor measured high concentration of PM2.5 (51 and 60 g/m3 at Home 063 and 068, respectively). Without the heated inlet, the co-located indoor monitor measured 111 and 78 g/m3, respectively. The two homes were sampled in winter (January 2018) in Tracy and Manteca CA, where high humidity condition in the morning likely explained this difference between the co-located indoor and outdoor PM2.5 monitors. Excluding these two cases, the co-located indoor and outdoor PM2.5 monitors agreed to within 1.9 g/m3 on average (median = 0.9 g/m3), with the outdoor monitor reporting lower concentrations than the indoor monitor in 79% of the indoor side-by-side deployments. This is likely because the heated inlet intended to prevent condensation resulted in some volatilization of organics in the outdoor particles. The results of the brief side-by-side deployment of indoor and outdoor MetOne photometers at each home are provided in Figure S2.

Figure S2. Results of side-by-side deployment of indoor and outdoor MetOne photometers at each house, typically outdoors.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-10
The Extech CO2 monitors were co-located for 1 hour at each home or at a warehouse where the field team prepared equipment before a visit. The field team confirmed that CO2 monitors agreed with one another to within a range of 100 ppm. Extech monitors were also calibrated at LBNL during two breaks in sampling, with 5 units checked during Feb 2017 and 7 units (including two from first round) checked during Dec 2017. On each occasion, the monitors were set up in a well-mixed room along with an EGM-4 gas analyzer (PP systems, Amesbury, MA, USA). The EGM-4 was separately calibrated using standard gas of known CO2 concentrations between 0 and 2500 ppm. During each event, CO2 concentrations in the chamber were raised by injection of pure CO2 then left to decay with air exchange. Hourly concentrations were calculated for each monitor. The first-hour means were 1056 and 1537 ppm for the two events. Decay periods were 26 and 7 hours to final-hour concentrations of 420 and 529 ppm. Hourly average concentrations reported by the Extech units differed (high to low range) by 71–86 ppm during the first spike- decay and 111–168 ppm during the second. Averaged over the full spike-decay intervals, differences between Extech units and the EGM-4 ranged from -20 ppm to 84 ppm.

The Aeroqual 500 NO2 monitor was calibrated before each visit with zero gas and a 1 ppm NO2 standard gas. Monitor response was adjusted to match those values following manufacturer instructions. Despite this calibration step, there was generally a substantial, positive offset in the time-integrated NO2 concentration measured by the Aeroqual when compared with the concentrations measured using the passive sampler. Further processing of the Aeroqual NO2 data is required, which is beyond the scope of this paper.

Weighing of Filters for Gravimetric PM2.5 Determination Gravimetric samples were collected on 37 mm diameter, 2.0 micron pore size, Pall Teflo filters with ring. Prior to deployment, filters were preconditioned for 24 hours at controlled temperature and humidity conditions (47.5 +/- 1.5 % RH and 19.5±0.5 ºC), passed over a deionizing source to remove static charge and weighed twice using a Sartorius SE2-F balance. Pre-weighed filters were loaded into the pDR-1500 photometers and were shipped to GTI for deployment. After a week of monitoring, GTI shipped the pDR monitors back to LBNL. LBNL removed the filters, and repeated the preconditioning and weighing procedures. The collected mass was determined as the post-sampling versus pre-sampling mass difference. The field blank was subtracted from the sample mass. Sampled air volume was taken from the pDR. Mass concentration was calculated as collected PM mass / sample air volume. The sample flow rate of the pDR was checked in the lab before and after each field use.

Passive Sampler Procedures and Quality Assurance
Ogawa samplers were prepared according to manufacturer protocols. Prior to assembly for field deployment, all parts of the samplers were washed thoroughly with deionized water and allowed to dry thoroughly in a laboratory at LBNL. Sample pads were stored in the refrigerator in their original packaging until they were inserted into samplers. After samplers were assembled with new sample pads, they were placed in sealed amber plastic bags (Ziploc) and shipped to the field team in an insulated box with ice packs to keep them cool.

All passive samplers were shipped to LBNL for analysis. To avoid damage to the chemical samplers from extreme temperatures, samplers were mailed in an insulated shipping container IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-11
with ice packs to keep them cool. The samples were extracted and analyzed following the protocols provided by each company (Ogawa & Company 2017; SKC, Inc. 2017). All Ogawa samples were extracted for analysis within 30 days from when the samplers were assembled.

For each NOX and NO2 sample we subtracted the mass determined from the field blank at the same home before calculating the sample period concentrations of NOX, NO2 and NO as the difference between the adjusted NOX and NO2 concentrations. For two homes that did not have a field blank, we subtracted 0.15 micrograms for NO2 and 0.22 micrograms for NOx, which are the mean mass determined from all available field blanks; these masses correspond to 0.9 ppb of NO2 and 1.3 ppb of NOx for a 7-day collection period. Following blank subtraction, 4 indoor and 5 outdoor NO2 samples and 1 indoor and 6 outdoor NOx samples had negative concentrations; the occurrence of negative values results from variability in the blank correction and low sample masses. These negative NO2 and NOx concentrations were retained when calculating summary statistics. Analysis of 64-paired duplicates of indoor samples found that agreement in NO2 concentrations was within 0.6 ppb on average (median = 0.3 ppb). When available, duplicates were averaged to provide a better estimate of the indoor concentrations of NO, NO2, and NOx.

Sampling rates were calculated using co-located temperature and relative humidity measurements following manufacturer instructions.

The formaldehyde concentration determined by passive sampler at each home also was adjusted by the effective sample period concentration determined from the field blank at the same home.

For the eleven homes that did not have a formaldehyde passive sample field blank, we subtracted

0.15 micrograms, which is the mean mass determined from all available field blanks (and corresponds to 0.6 ppb for a 7-day collection period). Sixty-six paired indoor formaldehyde samples agreed to within 1.0 ppb on average (median = 0.7 ppb). When available, duplicates were averaged to provide a better estimate of the indoor concentrations. A sampling rate of 20.4 ml/min were used following manufacturer instructions.

The UMEx contains an internal blank within each sampler that can potentially be used for convenience instead of deploying a separate field blank sampler. However, analysis of the internal blank suggested that even though it was not directly exposed to the sampling air, some formaldehyde was collected, possibly because the compartment isolating the internal blank was not completely airtight. The average analyte mass determined from internal blanks of indoor samples was 0.6 micrograms; this is 4 times the field blank value noted above.

Formaldehyde indoor emission rates E (g/m3-h) were calculated using a simple mass-balance equation assuming well-mixed, steady state condition. The same method was applied by Offermann (2009) to estimate indoor emission rates of formaldehyde and other VOCs.

E = (Ci – Co)AER (1)
Outdoor formaldehyde concentration (Co, g/m3) was subtracted from the indoor concentration (Ci, g/m3) measured at the central location, assuming that there is no loss in formaldehyde as the outdoor air enters through the building envelope. Air exchange rate (AER, 1/h) is assumed to be the only mechanism that removals formaldehyde from the indoor air. Air exchange rate was estimated from natural infiltration airflow and mechanical airflow using sub-additivity, as described later in the Methods.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-12
Potential Impact of Low Air Speeds on Passive Sampler Data The sampling rates of passive samplers may be impacted by low air speeds at the sampler inlet, as discussed by Offermann and Hodgson (2018)1 and papers cited therein. At very low air speeds, diffusive uptake to the passive sampler causes a reduction in analyte concentration at the face of the air sampler relative to the surrounding indoor air, resulting in an effective increase in the diffusive path length and lower sampling rate.

Since air speeds were not measured in HENGH homes, we rely on the data of Mathews et.al. (1989)2 to assess the potential for low air speeds to bias the passive sampler measurements in residences. Matthews et al. used a TSI Model 1620 omnidirectional anemometer to measure air speeds during daytime hours in various rooms of six occupied homes and in an unoccupied research house. The overall median air speed measured in the six occupied homes was 318 cm/min. HVAC operation was found to substantially impact air speeds, by a factor of 5 in one house and by roughly a factor of 2 in two other occupied houses. The median measured air speeds with HVAC off in three occupied homes and the research house were 90, 198, 342, and 246 cm/min. Among the rooms studied, air speeds were lowest in the master bedroom, with median values during no HVAC use of 108 cm/min across the three occupied houses. The condition with the lowest measured air speeds was in a bedroom that was completely unoccupied; during HVAC off times median air speeds were 66 cm/min. HVAC operation was not tracked in HENGH; but the median HVAC run time was 1.1 h per 24 h in the CNHS.

Using a TSI Model 8475 omnidirectional anemometer, Offermann and Hodson reported an air speed of 27 cm/min in an unoccupied office overnight with no HVAC operation.

Using the data above as reference points, Offermann provided the following correction factors for the geometries of the UMEx and Ogawa samplers at selected air speeds.

Air Speed (cm/min) UMEx CF Ogawa CF
27 1.21 1.16
66 1.09 1.07
100 1.06 1.04
300 1.02 1.01
Using the daytime airspeeds measured with no HVAC operation and assuming that condition applied roughly half the time in HENGH master bedrooms, and also assuming higher airspeeds with occupancy during nighttime hours, the bias from low air speeds would be on the order of 3% for formaldehyde and 2% for NOX and NO2. A bedroom that is completely unoccupied during the daytime and similar to the one reported in Matthews could have a bias of 4-5% for formaldehyde and 3-4% for NOX and NO2. If any rooms commonly experienced conditions similar to those observed overnight in the Offermann office, the bias would be 8-10%.

1 Offermann, F. J. and A. T. Hodgson (2018). Accurancy of Three Types of Formaldehyde Passive Samplers. Indoor Air 2018, Philadelphia PA, International Society of Indoor Air Quality Sciences. 2 Matthews, T. G., C. V. Thompson, D. L. Wilson, A. R. Hawthorne and D. Mage (1989). "Air velocities inside domestic environments: An important parameter in the study of indoor air quality and climate." Environment International 15: 545-550.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-13

Adjustments to Formaldehyde Data from FM-801 Monitor
Output of the FM-801 formaldehyde monitor dropped precipitously during events of substantial gas cooking burner use, presumably owing to an NO2 interference as described by Maruo et al.3 FM-801data that were clearly affected by cooking were identified by visual review, considering data from the time-resolved NO2 monitor and the cooktop and oven temperature sensors, and removed. Data marked as “<LOD” because they were below the 10 ppb quantitation limit were assigned a value of 7.3 ppb based on analysis of data from homes with the modified FM- 801software that provided numerical results below 10 ppb.

Calculation of Outdoor Air Exchange Rate
First, mechanical fan flows were calculated by summing exhaust fan flows (whole house exhaust fan, and other fans in bathroom, range hood, clothes dryer) weighted by their average usage time.

Since it was not practical to directly measure the airflow of the clothes dryers in most homes, we assumed dryer airflow of 125 cfm based on a recent report4.

Airflows from mechanical fans were added to calculate balanced (Qbalance_mech) and unbalanced (Q unbalance_mech) airflows by comparing minute by minute the amount of exhaust and supply air from usage data collected from each home. Next, air infiltration (Qinfiltration) was calculated using the flow coefficients and pressure exponents from average of pressurization and depressurization tests of building envelope leakage, determined as part of the DeltaQ Test, and using stack and wind coefficients following the ASHRAE Fundamentals Enhanced Model. Wind data were obtained from the nearest weather station5. Indoor and outdoor temperatures were monitored onsite. Photos of the house and surroundings were reviewed to determine the appropriate shelter class: either 4 (urban building on larger lots where sheltering obstacles are more than one building height away) or 5 (shelter produced by buildings or other structures that are closer than one house height away). The total ventilation rate was calculated following Equation 2, which uses a superposition adjustment (∅) to account for the sub-additivity of unbalanced mechanical airflows with air infiltration.

𝑄𝑡𝑜𝑡𝑎𝑙 = 𝑄𝑏𝑎𝑙𝑎𝑛𝑐𝑒_𝑚𝑒𝑐ℎ + 𝑄𝑢𝑛𝑏𝑎𝑙𝑎𝑛𝑐𝑒_𝑚𝑒𝑐ℎ + ∅𝑄𝑖𝑛𝑓𝑖𝑙𝑡𝑟𝑎𝑖𝑡𝑜𝑛 (1) ∅=
Qinfiltration
Qunbalance_mech+Qinfiltration
(2)
Field teams measured ceiling heights in the great room, kitchen, living room, dining room, bedrooms, and other parts of the house. Air exchange rate was computed using an approximate house-averaged ceiling height and floor area recorded by the field team.

3 Maruo, Y. Y., T. Yamada, J. Nakamura, K. Izumi and M. Uchiyama (2010). "Formaldehyde measurements in residential indoor air using a developed sensor element in the Kanto area of Japan." Indoor Air 20(6): 486-493. 1 ENERGY STAR reports rated fan flow of clothes dryer typically range between 100 and 150 cfm. https://www.energystar.gov/sites/default/files/asset/document/ENERGY_STAR_Scoping_Report_Residential_Clot hes_Dryers.pdf
5 Data obtained from www.wunderground.com. During periods when wind was reported as “calm”, 1 mph (mile per hour) was assumed for calculating air infiltration rate.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-14
Estimate of Potential Bias in Calculated Air Infiltration While the ASHRAE Enhanced Model was developed from an extensive set of measured data and has been evaluated in several previous studies6,7,8, it is nevertheless valuable to consider that it could have varied performance in specific applications.

For this study, we used data from the CNHS – which measured time-integrated outdoor air ventilation rates using perfluorocarbon tracer gases (PFTs) – to evaluate the method used to calculate the infiltration portion of air exchange in HENGH, which measured mechanical airflows but calculated infiltration and overall AER.

The analysis looked at 13 CNHS homes that that had no window opening and no continuous mechanical ventilation (just occasional bathroom, kitchen, and clothes dryer exhausts); the overall AERs in these homes were thus dominated by infiltration. For these 13 homes, we calculated infiltration/air exchange in the same manner as was done for the HENGH study. (The only difference was that the calculation was done with 1-minute indoor temperature and intermittent exhaust fan data for HENGH and 15-minute data for CNHS. The calculations used the following parameters:
 default stack and wind coefficients for n=0.67;
 on-site data for indoor air temperature and local Meteorological Station data for outdoor air temperatures and wind speeds;
 setting all 0 mph wind speeds to 1 mph;
 using the interpolated ASHRAE Fundamentals Shelter Factors;  combining any intermittent mechanical airflow with infiltration using sub-additivity;  calculating the weekly integrated AER as the harmonic mean of 15-min estimates.

For each of the 13 CNHS homes, we compared the AER measured by PFT to the calculated AER to determine a correction factor, which we consider to be applicable to the calculated infiltration portion of AER. The median correction factor for the 13 homes was 1.81 with a range of 1.04 –

2.11. While this is high compared to published comparisons of measurements to infiltration model calculations, our hypothesis is that it is mostly due to the difficulty in selecting appropriate wind shelter factors.

Since most of the HENGH homes had continuous mechanical exhaust systems, infiltration accounted for only a fraction of the total outdoor air exchange. To assess the potential impact of infiltration bias calculated for the CNHS homes on the AERs calculated for HENGH homes, we

6 Walker, I.S. and Wilson, D.J., (1998), “Field Validation of Equations for Stack and Wind Driven Air Infiltration Calculations”, ASHRAE HVAC&R Research Journal, Vol. 4, No. 2, pp. 119-140. April 1998. ASHRAE, Atlanta, GA. LBNL 42361.
7 Francisco, P. and Palmiter, L. (1996). “Modeled and Measured Infiltration in Ten Single-Family Homes. Proc.

ACEEE 1996.
8 Wang, W., Beausoleil-Morrison, I. and Readon, J. 2008. Evaluation of the Alberta Air Infiltration Model Using Measurements and Inter-Model Comparisons. Building and Environment, 44. 309-318. doi:10.1016/j.buildenv.2008.03.005c

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-15
adjusted the calculated infiltration rates for all HENGH homes by a factor of 1.81, then used sub- additivity to combine the adjusted infiltration rates with the measured mechanical ventilation rates on a home-by-home basis. The median calculated adjustment factor for the total ventilation rates for HENGH homes is 1.18.

In addition to the potential bias from infiltration calculations, the calculated AERs for HENGH homes are also biased in some cases because the calculation assumed no window or door opening; any substantial use of windows or doors for ventilation would further raise AERs relative to calculated values.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-16
Results
House Characteristics
Table S3. Sampled Homes by Cities and Climate Zones (N=70) Gas
Utility
Service
Cal.

Climate
Zone
Cities (Number of Homes) Homes Total
PG&E 3 Discovery Bay (2), Hayward (2), Oakland (1) 5 48 11 Marysville (1) 1
12 Brentwood (12), El Dorado Hills (10), Elk Grove (6), Manteca (4), Mountain House (2), Pittsburg (2), Davis (1), Dublin (1), Sacramento (1)
39 13 Clovis (3) 3
SoCalGas
8 Irvine (2), Downey (1), Lake Forest (1), Yorba Linda (1) 5 22 9 Van Nuys (5), Alhambra (1) 6
10 Jurupa Valley (5), Chino (4), Corona (1), Eastvale (1) 11

Table S4. Sampled Homes by Seasons
Season Months Number of Homes
Winter Dec-Feb 16
Spring Mar-May 13
Summer Jun-Sep 27
Fall Oct-Nov 14
Total 70
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-17
Table S5. Sampled Homes by Year Built
Year Built Number of Homes
2011 1
2012 7
2013 13
2014 17
2015 15
2016 14
2017 3
Total 70

Table S6. Age of Homes When Sampled1
HENGH Age When
Sampled (years)
HENGH Number of
Homes at Age
CNHS Percentile CNHS Age When
Sampled (years)
<1 2 Min 1.7
1 14 10th 2.4
2 32 25th 3.0
3 14 50th 3.4
4 4 75th 4.0
5 2 90th 4.3
No Response 2 Max 5.5
Total N=70 N=108
1 CNHS data from Table 15 of Offermann et al. (2009)

Table S7: Sampled Homes by Floor Area
Floor Area (ft2) Homes Floor Area (m2) Homes
<1500 5 <150 9
1500–1999 11 150–199 12
2000–2499 16 20–-249 15
2500–2999 16 250–299 22
3000–3499 14 300–349 6
3500 8 3500 6
Total 70 Total 70
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-18

Table S8: Sampled Homes by Number of Stories
Stories Number of Homes
1 27
2 42

2.5 1
Total 70

Table S9: Sampled Homes by Number of Bedrooms
Bedrooms Number of Homes
1 1
2 3
3 20
4 28
5 17
6 1
Total 70

Table S10: Sampled Homes by Number of Bathrooms
Bathrooms Number of Homes
1–1.5 1
2–2.5 24
3–3.5 35
4–4.5 9
5–5.5 1
Total 70

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-19
Table S11: Locations of Gas Fireplaces
Location Homes
Great room or living room 26
California room 3
Courtyard 1
Patio 2
No gas fireplace 38
Total 70

Household Demographics
HENGH homes are compared with data from American Housing Survey (2017 AHS). Data from the Public Use File (PUF)9 were used to compare with demographic data of HENGH homes. The PUF provided data for four California metropolitan areas that were surveyed in 2017: Los Angeles-Long Beach-Anaheim, San Francisco-Oakland-Hayward, Riverside-San Bernardino- Ontario, and San Jose-Sunnyvale-Santa Clara. The first three of the four metropolitan areas were included in the national survey, and the last one was included in the metropolitan survey. Data from owner-occupied, single-family detached homes built after 2010 were selected from the 2017 AHS data for comparison with HENGH homes in the tables below.

Table S12: Number of Occupants in Sampled Homes
Number of Occupants Number of Homes
in HENGH
% Homes in
HENGH
% Homes in 2017
AHS
1 3 4% 13%
2 29 43% 28%
3 10 15% 18%
4 13 19% 24%
5 6 9% 9%
6 3 4% 5%
7 or more 3 4% 2%
No response 3 -- --
Total 70 100% 100%

9 https://www.census.gov/programs-surveys/ahs/data/2017/ahs-2017-public-use-file--puf-.html

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-20

Table S13: Number of Occupants in Sampled Homes by Age Group Number of
Occupants
Within Age
Group
Homes with Designated Number of Occupants in Designated Age Group Number of HENGH % HENGH Homes % Homes in 2017 AHS
Age
0–17
Age
18–65
Age
65+
Age
0–17
Age
18–65
Age
65+
Age
0–17
Age
18–65
Age
65+
0 41 8 49 60% 12% 72% 59% 12% 74%
1 7 7 10 10% 10% 15% 19% 17% 14%
2 14 41 9 21% 60% 13% 18% 42% 11%
3 3 8 0 4% 12% 0% 4% 15% 0%
4 2 2 0 3% 3% 0% 0% 9% 0%
5 or more 1 2 0 1% 3% 0% 0% 5% 0%
No response 2 2 2 -- -- -- -- -- --
Total 70 70 70 100% 100% 100% 100% 100% 100%

Table S14: Total Household Income in Sampled Homes
Income Range Number of Homes
in HENGH
% Homes in
HENGH
% Homes in 2017
AHS
$35,000–$49,999 1 2% 18%
$50,000–$74,999 2 3% 12%
$75,000–$99,999 5 8% 10%
$100,000–$150,000 29 44% 20%
Greater than $150,000 29 44% 40%
No response 4 -- --
Total 70 100% 100%

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-21
Table S15: Education Level of Head of Household in Sampled Homes Education Level Number of Homes
in HENGH
% Homes in
HENGH
% Homes in 2017
AHS
No diploma 0 0% 6%
Completed high school 1 1% 16%
Some college 5 7% 15%
Associate’s degree 2 3% 7%
College degree 23 34% 30%
Graduate or professional degree 36 54% 26%
No response 3 -- --
Total 70 100% 100%

Air Tightness

Figure S3: Distribution of ACH50 from Envelope Leakage Measurements

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-22

Ventilation and Filtration Equipment
Table S16: Whole House Ventilation System Type
System Type Operation Mode Fan Location(s) Number of Homes Exhaust Continuous Laundry Room 43
Bathroom 9
Attic 3
Intermittent Laundry Room 5
Bathrooms (multiple) 4
Supply Continuous Attic 4
Intermittent None* 2
Total 70
*These central fan integrated supply (CFIS) systems had a duct with motorized damper that connected the outdoors to the return side of the forced air system, but no supply fan.

Table S17: Whole House Ventilation System Control
Whole-House Ventilation Control Controller Labelled? % On As-Found On/Off Switch No (N=42) 5%
Yes (N=12) 58%
Programmable Controller No (N=10) 50%
Thermostat No (N=2) 0%
Breaker Panel No (N=1) 100%
No Controller No (N=3) 100%

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-23

Figure S4: Bathroom Exhaust Fan Measured Flow Rates

Table S18: Air Filter MERV Ratings
MERV Number of Air Filters
6 2
7 2
8 57
10 17
11 22
12 1
13 9
14 1
Total 111

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-24
Table S19: Time Since Last Air Filter Change
Marked or Estimated Time Number of Air Filters
0 to 2 Months 33
3 to 5 Months 16
6 to 8 Months 17
12 to 15 Months 8
Never Changed 11
Total 85

Table S20: Condition of Air Filters Observed by Field Team Air Filter Condition Number of Homes Number of Air Filters Clean or Like New 20 39
Used or Dirty 29 65
Very Dirty 18 24
Total 67* 128
* Total excludes one home (113) without a central forced air system (this home had a minisplit heat pump with no filter for air quality), one home (127) without any air filters installed in the return air registers, and one home (117) for which field observations were missing.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-25

Figure S5: Total Estimated Air Exchange Rate
This plot includes estimates for 63 homes. It excludes four homes that used supply ventilation because the mechanical airflow could not be determined. The plot also excludes three homes with missing DeltaQ test result because building envelope airtightness is required to calculate air infiltration (part of total ventilation). There are six homes (*) where opening of the house-to-patio and/or garage door(s) for more than 3 hours per day on average may have increased the overall AER substantially.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-26

Figure S6: Infiltration and Total Airflow (Mechanical + Infiltration) Mechanical airflow rates were calculated by summing all exhaust fans in a home. The estimated total outdoor airflow rates include both mechanical airflow and air infiltration. Data are plotted for 63 homes same as in Figure S5.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-27
General Occupancy and Sources – From Survey
Table S21: How Frequently Are Candles Used in the Home
Number of Homes
Never 13
A few times a year 23
A few times a month 16
A few times a week 11
Every day 5
No response 2
Total 70

Table S22: Number of Furry Pets in Homes

Occupancy and Sources During Week of Monitoring
Table S23: Self-Reported Average Occupancy (Number of People) When Home Was Occupied Average Occupancy Number of Homes Average Occupancy Number of Homes 1 to <2 People 23 5 to <6 People 4
2 to <3 People 20 6 to <7 People 3
3 to <4 People 14 No Response 2
4 to <5 People 4 Total 70

Number of Pets Number of Homes
0 20
1 17
2 12
3 3
4 or more 2
No response 16
Total 70
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-28
Table S24: Self-Reported Average Occupied Hours per Day During Monitoring Week Number of Occupied Hours Number of Homes
> 23 Hours 16
20 to <23 Hours 27
16 to <20 Hours 17
12 to <16 Hours 3
6 to <12 Hours 3
< 6 Hours 2
No Response 2
Total 70

Table S25: Self-Reported Cooktop Use (Number of Times) During Monitoring Week Number of Cooktop Use Number of Homes
None 2
1–3 Times 16
4–6 Times 16
7–14 Times 26
15–21 Times 6
More than 21 Times 2
No Response 2
Total 70

Table S26: Self-Reported Oven and Outdoor Grill Use During Monitoring Week Number of Homes
Number of Uses Oven Outdoor Grill
None 16 52
1 Time 14 9
2–3 Times 21 7
4–5 Times 11 0
6–8 Times 6 0
No Response 2 2
Total 70 70
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-29

Table S27: Average Cooking Activity Duration During One-Week Monitoring, Self-Reported Number of Homes
Use Duration Cooktop Oven Outdoor Grill
Less than 10 Minutes 3 3 0
10–30 Minutes 40 20 5
30–60 Minutes 20 24 8
>60 Minutes 3 5 3
No Usage Reported 2 16 52
No Response 2 2 2
Total 70 70 70

Table S28. CNHS Activities (Table 42 and 43 of Offermann et al. 2009):
- Toasting: n=50, median of 5 min
- Frying or sautéing: n=36, median of 17 min
- Baking: n=33, median of 45 min
- Broiling: n=11, median of 19 min
- Other cooktop: warming/boiling, n=47, median of 20 min - Vacuuming: n=16, median of 25 min
- Sweeping or dusting: n=16, median of 12 min
- Candle burning, n=4 events, median of 165 min.
- Aerosol air fresheners or personal care products: n=30 - Large party or dinner gathering: n=3
- Other activities: dust, smoke or fumes: n=3, median 30 min

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-30
Air Pollutant Concentrations: Formaldehyde
Table S29 presents a comparison of formaldehyde measurements made at the main indoor site with the UMEx-100 time-integrated sampler and the weeklong average of the half-hourly resolved data obtained with the FM-801 monitor. Statistical significance tests suggest no difference in formaldehyde concentrations measured using the two methods: p-value = 0.09 (Student’s paired t-test).

Table S29: Comparison of Time-Integrated Formaldehyde Measured with Two Methods SKC UMEx-100
Passive Sampler
GrayWolf FM-801
Monitor
Indoor Main (ppb) N = 68 N = 69
Mean 19.8 18.9
Median 18.2 18.8
10th–90th Percentile 13–28 10–27

Similar to the finding (reported in the main paper) that formaldehyde measured by the UMEx was higher in the bedroom than at the main indoor site, FM-801 data collected in the bedroom also indicated higher period-averaged formaldehyde compared to data collected in the main indoor site (p-value = 4.5e-5 using Student’s paired t-test). Among the 65 homes with valid FM- 801 data in both locations, formaldehyde in the bedroom was >10% higher than in the living room in 35 homes and less than 90% in 4 homes. The median and 10th–90th ratios of bedroom to living room concentrations were 1.13 and 0.97–1.44. Using data from the FM-801, overnight concentrations in the bedroom were higher than the period-average at that location (p-value =

5.4e-6 using Student’s paired t-test). Formaldehyde in the bedroom overnight was >10% higher than the period-average living room in 38 homes and less than 90% in 3 homes. The median and 10th–90th ratios of bedroom overnight to period-average living room concentrations were 1.19 and 0.97–1.52.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-31
Air Pollutant Concentrations: PM2.5
A comparison of time-integrated PM2.5 measured with the MetOne and Thermo pDR photometers and co-located gravimetric samples are provided in Table S30. Table S30 Table S30. Time-integrated PM2.5 concentrations measured by MetOne and Thermo pDR-1500 photometers compared with gravimetric analysis of co-located filter samples.

House City Dates MetOne pDR Filter Filter/
MetOne
Filter/
pDR
Indoor PM2.5 (ug/m3)
025 Hayward 2017-03-23 to 03-30 3.7 4.5 4.7 1.3 1.1
026 Davis 2017-04-18 to 04-25 2.8 4.3 4.2 1.5 1.0
040 Discovery Bay 2017-05-23 to 05-30 2.1 3.2 2.8 1.3 0.9 029 Brentwood 2017-06-09 to 06-16 3.1 3.8 3.7 1.2 1.0
047 Clovis 2017-10-12 to 10-19 31.9 30.1 23.5 0.7 0.8
046 Clovis 2017-11-08 to 11-15 5.1 6.9 5.0 1.0 0.7
068 Manteca 2018-01-24 to 01-31 2.6 4.2 3.6 1.4 0.9
066 Manteca 2018-02-05 to 02-12 2.7 4.3 4.0 1.4 0.9
Outdoor PM2.5 (ug/m3)
025 Hayward 2017-03-23 to 03-30 NA 5.6 4.1 NA 0.7
026 Davis 2017-04-18 to 04-25 NA 3.4 4.4 NA 1.3
040 Discovery Bay 2017-05-23 to 05-30 4.5 5.1 4.8 1.1 0.9 029 Brentwood 2017-06-09 to 06-16 3.0 3.9 3.4 1.1 0.9
047 Clovis 2017-10-12 to 10-19 25.5 30.3 19.6 0.8 0.6
046 Clovis 2017-11-08 to 11-15 6.0 NA NA NA NA
068 Manteca 2018-01-24 to 01-31 20.2 18.2 10.6 0.5 0.6
066 Manteca 2018-02-05 to 02-12 14.0 12.4 5.6 0.4 0.4

Analysis of Regulatory Air Monitoring Data to Estimate PM2.5 Outside of HENGH Homes We investigated the possibility of using regulatory ambient air monitoring station data to develop correction factors for photometers outside of the homes. We identified up to three regulatory air monitoring stations near each of the study home. Figure S1 show locations of the air quality monitoring stations in relationship to the study home. The air monitoring stations were all located within 30 km of the study home, selected to broadly represent the air quality at that location. Air monitoring stations sited to monitor near-road concentrations (located within 100 m of a major roadway) were excluded to avoid biases from traffic emissions. The daily mean PM2.5 were obtained from AQMIS.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-32
We applied inverse distance weighting to calculate the daily mean PM2.5 at the study home, and calculated the mean PM2.5 for the monitoring period (~6 days). Results of the inverse distance weighted ambient monitoring data are compared with the outdoor PM2.5 measured using MetOne photometer in Error! Reference source not found..

Table S31 shows the differences in mean PM2.5 measured using the MetOne photometer and inverse distance weighted ambient monitoring data. Because the ambient monitoring data obtained from AQMIS are daily means, the results presented in Table S31Table S31 considered only days with full 24-h data as monitored by the MetOne photometer (i.e., partial days on first and last day of monitoring were excluded). The mean, median, and 10th percentile estimates of PM2.5 measured by the MetOne photometer were less than what was measured at the corresponding ambient monitoring station. This suggests that the MetOne photometer may have underestimated the outdoor PM2.5 relative to the ambient monitoring data at some of the homes.

However, the reverse is true for other homes such that the MetOne photometer measurements were higher than the ambient monitoring data when compared at 90th percentile. No correction factor is applied to outdoor MetOne because of a lack of consistency when compared with the ambient monitoring data.

Table S31. Summary statistics (N=67) of the mean outdoor PM2.5 measured using MetOne photometer and inverse distance weighted ambient monitoring data.

MetOne photometer
(ug/m3)
Nearby ambient air quality
monitoring stations (ug/m3)
Mean 9.3 10.5
Median 6.8 9.7
10th–90th 2.7–18.1 5.3–16.7

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-33

Figure S7. Comparison between mean outdoor PM2.5 measured using MetOne photometer and inverse distance weighted ambient monitoring data (N=67).

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-34
Air Pollutant Concentrations: Nitrogen Dioxide and Nitric Oxide

Figure S8: One-Week Integrated NO2, NO, and NOx Concentrations Ranked ordered by indoor concentrations (blue circles), with corresponding outdoor concentrations plotted as black crosses.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-35
Air Pollutant Concentrations: CO2

Figure S9: Overnight (midnight-5am) CO2 measurements in indoor main living space and master bedroom.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-36
IEQ Satisfaction by Ventilation System Operation
Tables S33 to S35 present air quality and comfort satisfaction reported by participants, divided by whether the dwelling unit ventilation system was operating when the research team arrived to the home. The Fisher’s exact test for count data was performed to determine if there is an association between the ventilation system operating at that time and satisfaction. Survey responses for satisfaction were scored using a scale between 1 and 9. For the Fisher’s test, satisfaction responses were classified into four groups: dissatisfied (1–4), neutral (5), satisfied (6–7), and very satisfied (8–9). Survey responses for frequency of a discomfort were provided using a 5-level scale: (i) never, (ii) a few times a year, (iii) a few times a month, (iv) a few times a week, and (v) every day. For the Fisher’s test, frequency responses were classified into two groups: infrequent (i, ii, or iii) and frequent (iv or v).

Table 32. Air quality satisfaction reported by participants.

To what extent are you
satisfied or dissatisfied with
indoor air quality in your
home?
How would you rate the
outdoor air quality where
you live?
How would you rate your
home in protecting you
from outdoor air pollution?
Ventilation
As-Found
Off On Off On Off On
Dissatisfied 3 3 11 8 3 2
Neutral 13 3 9 2 18 3
Satisfied 17 4 17 6 15 6
V. Satisfied 17 8 10 2 14 7
p-value 0.375 0.413 0.444

Table 33. Satisfaction with seasonal temperature conditions by ventilation system status on first visit to home.

Winter / Some
rooms are too hot1
Winter / Some
rooms are too cold1
Summer / Some
rooms are too hot1
Summer / Some
rooms are too cold1
Ventilation
As-Found
Off On Off On Off On Off On
Infrequent 41 13 36 10 37 9 45 15
Frequent 6 4 12 8 13 9 2 1
p-value 0.435 0.144 0.081 1
1 Survey question: In [season], how often is the temperature in your home uncomfortable to any occupants because [condition]?

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-37
Table 34. Satisfaction with environmental parameters by ventilation system status on first visit to home.

Too much air
movement
Not enough air
movement
Indoor air is
too dry
Indoor air is
too damp
Indoor air has
musty odor
Ventilation
As-Found
Off On Off On Off On Off On Off On
Infrequent 48 18 41 11 43 17 49 18 48 17
Frequent 1 0 8 7 5 1 1 0 1 0
p-value 1 0.094 1 1 1
1 Survey question: How often do the following conditions affect the comfort of occupants in your home? Frequent is on weekly or daily basis.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-38
Recruitment Postcard

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-39
Daily Activity Log
Provided below is the top page of the activity log. Participants were asked to complete a log table for each calendar day during which measurements were being made in the home. Participants were provided with paper sheets containing a log for each day.

Healthy Efficient New California Homes Study
Occupancy and Indoor Activities Data Log

Instructions: Please fill out this data log each day, or on the following day.

Please enter your best estimates. If you are unsure, please provide your best guess.

Do not list the names of any people.

Code number for home _________

Day 1: Date __________________ Date completed _______________ Midnight
to 7am
7am to
11am
11am to
1pm
1pm to
5 pm
5pm to
9pm
9pm to
Midnight
Number of people
in home

Cooktop use
Number of minutes

Oven use
Number of minutes

BBQ/outdoor grill
Number of minutes

Vacuuming
Number of minutes

Window Use
Number of minutes

Other notable*
indoor/outdoor events

* For example, use of fireplace, candle, air freshener, air cleaner, humidifier, unusual outdoor air quality (wood smoke, wildfire), and so on.

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-40
Occupant Survey

Welcome to the 2015 California New Homes Survey!
This survey is part of a research study on new homes in California. This research will help inform how new homes can provide adequate ventilation and good indoor air quality, while reducing air infiltration and energy use.

This survey takes about 15 minutes to complete. It asks questions about your home, household activities, and demographics. You can skip questions that you do not want to answer.

This research is being conducted by Lawrence Berkeley National Laboratory (LBNL) with funding from the California Energy Commission. Results will be used only for research on how to provide adequate ventilation and improve indoor air quality. In order to protect your privacy, the data will be encrypted and password protected.

Please return your completed survey in the envelope provided.

If you have questions about the research study, please contact:

Max Sherman, Ph.D.

Principal Investigator, Residential Building Systems Group Lawrence Berkeley National Laboratory
[email protected] (510) 486 4022

Code number for home _________ Date completed _______________

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-41
Please answer to the best of your knowledge. You can skip any questions that you do not want answer.

A. Home and Household Characteristics

1. What year was your house built?
Year Built: ………………

2. What is the size (floor area) of your home?
Square Feet: ………………

3. What year did you move into this home?
Year Moved In: ……………….

4. Do you own or rent your home?
……. Own (If yes  5, skip otherwise)
……. Rent
……. Other

5. Are you the first owner of the property? Yes / No

6. How many people currently live in your home?
Number of People: ……………..

B. Air Quality In and Around Your Home

7. To what extent are you satisfied or dissatisfied with the indoor air quality in your home? Very
Dissatisfied
Neutral Very
Satisfied
☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐

8. How would you rate the outdoor air quality near where you live? Very
Poor
Neutral Excellent
☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐

9. How would you rate your home in protecting you from outdoor air pollution? Very
Ineffective
Neutral Very
Effective
☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-42

C. Comfort Level in Your Home

10. In winter, how often is the temperature in your home uncomfortable to any occupants because some room(s) are too hot or too cold?

Never Few times
a year
Few times
in a month
Few times
a week
Every
day
Too hot in some room(s). ☐ ☐ ☐ ☐ ☐
Too cold in some room(s). ☐ ☐ ☐ ☐ ☐

11. In summer, how often is the temperature in your home uncomfortable to any occupants because some room(s) are too hot or too cold?

Never Few times
a year
Few times
a month
Few times
a week
Every
day
Too hot in some room(s). ☐ ☐ ☐ ☐ ☐
Too cold in some room(s). ☐ ☐ ☐ ☐ ☐

12. How often do the following conditions affect the comfort of occupants in your home?

Never Few times
a year
Few times
a month
Few times
a week
Every
day
Too much air movement. ☐ ☐ ☐ ☐ ☐
Not enough air movement. ☐ ☐ ☐ ☐ ☐
Indoor air is too dry. ☐ ☐ ☐ ☐ ☐
Indoor air is too damp. ☐ ☐ ☐ ☐ ☐
Indoor air has musty odor. ☐ ☐ ☐ ☐ ☐

IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-43
D. Natural Gas Appliances and Mechanical Ventilation

13. Which of the following heating appliances are used in your home? Select all that apply. ..….. Central gas furnace
……. Gas fireplace/ log set
….... Gas wall furnace
……. Freestanding gas heater
……. Central electric heating or heat-pump
……. Baseboard electric wall heater
……. Freestanding electric heater
……. Wood fireplace
……. Freestanding propane heater
……. Freestanding kerosene heater
……. Other. Please describe: ...………………………….
……. Don’t know

14. How often is the kitchen range hood or kitchen exhaust fan used when cooking with a cooktop?
……. Always (5 out of 5 times)
……. Most of the Time (4 out of 5 times)
……. Sometimes (2 to 3 out of 5 times)
……. Rarely (1 out of 5 times)
……. Never (0 out of 5 times)
……. Don’t know

15. If the kitchen range hood or kitchen exhaust fan is NOT always used, what are the reasons for not using it? Select all that apply.
……. Forget to turn it on
……. Not needed for what is being cooked
……. Too noisy
……. Doesn’t seem to remove cooking fumes or odors
……. Open window instead
……. Uses too much energy
……. Other. Please describe: ……………........................................

16. Was the operation of the mechanical ventilation system explained to you when you bought or moved into the home?
……. Yes
……. No
……. Don’t know

17. Do you feel you understand how to operate your mechanical ventilation system properly? ……. Yes
……. No
……. Not Sure
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-44

18. To what extent are you satisfied or dissatisfied with your mechanical ventilation system? Very
Dissatisfied
Neutral Very
Satisfied
☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐

19. If you are NOT very satisfied with your mechanical ventilation system, what are the reason(s) for dissatisfaction? Select all that apply.
……. Too noisy
……. Too drafty
……. Difficult to operate
……. Difficult to maintain
……. Uses too much energy
……. Brings in dust, odor, or air pollutants from outdoor ……. Not effective
……. Other. Please describe: ………………………………….

E. Occupancy and Indoor Activities

20. On average, how many hours per day is your home occupied by at least one person, including day and night hours?

Fewer than 8
hours per
day
8 to 12 hours
per day
12 to 16
hours per
day
16 to 20
hours per
day
More than 20
hours per
day
Weekday ☐ ☐ ☐ ☐ ☐
Weekend ☐ ☐ ☐ ☐ ☐

21. On average, how many times per week is your cooktop and/or oven used for cooking, including boiling water?

0 time
per week
1 to 2 times
per week
3 to 4 times
per week
5 to 6 times
per week
7 times
per week
Breakfast ☐ ☐ ☐ ☐ ☐
Lunch ☐ ☐ ☐ ☐ ☐
Dinner ☐ ☐ ☐ ☐ ☐
Other cooking ☐ ☐ ☐ ☐ ☐
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-45

22. On average, how many times per week do the following activities occur inside your home? Enter “0” if occurrence is less frequent than once a week.

Use shower (Times per week) …………………
Use bath or indoor Jacuzzi (Times per week) …………………
Use dishwasher (Times per week) …………………
Use washing machine (Loads per week) ………………..

Hang clothes to dry indoors (Loads per week) ………………..

F. Window Opening

23. On average, how many hours per day are your windows open?

0 hour per
day
1 to 2 hour
per day
2 to 8 hours
per day
8 to 16
hours per
day
More than 16
hours per day
Summer ☐ ☐ ☐ ☐ ☐
Fall ☐ ☐ ☐ ☐ ☐
Winter ☐ ☐ ☐ ☐ ☐
Spring ☐ ☐ ☐ ☐ ☐

G. Indoor Activities

24. On average, how often do the following activities occur inside your home?

Never Few times
a year
Few times
a month
Few times
a week
Every
day
Smoking ☐ ☐ ☐ ☐ ☐
Burn candle or incense ☐ ☐ ☐ ☐ ☐
Vacuuming ☐ ☐ ☐ ☐ ☐
Use cleaning agent for floor
cleaning
☐ ☐ ☐ ☐ ☐
Use spray air freshener ☐ ☐ ☐ ☐ ☐
Use pesticide spray ☐ ☐ ☐ ☐ ☐
Use paints, glue, solvents (e.g.,
hobbies, home repairs)
☐ ☐ ☐ ☐ ☐
Use humidifier ☐ ☐ ☐ ☐ ☐
Use dehumidifier ☐ ☐ ☐ ☐ ☐
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-46

H. Other Indoor Sources

25. Are plug-in or stick air fresheners, or other scented decorations, used in your home? ……. Yes
……. No
……. Don’t know

26. Do occupants wear shoes in your home?
……. Yes
……. No
……. Don’t know

40. How many dogs, cats, or other furry pets are in the home? Number of Pets: ………………

I. Use of Air Cleaners

27. Do you use a stand-alone (portable) air filter, air purifier, or air cleaner in the home? ……. Yes
……. No
……. Don’t know

28. Where is your stand-alone (portable) air filter, air purifier, or air cleaner located in your home? Select all that apply.
……. Master bedroom
……. Other bedroom(s)
……. Living room
……. Home office
……. Other. Please describe: ……………........................................

29. Has anyone in the household been diagnosed with asthma? ……. Yes
……. No
……. Don’t know

30. Has anyone in the household been diagnosed with allergies? ……. Yes
……. No
……. Don’t know
IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-47

J. Demographic Information

The next questions will help us interpret the results of the survey. All responses will be kept confidential.

31. Please indicate the number of household member(s) in the following age categories.

Number of household member(s)
0 to 17 Years Old ……………………
18 to 65 Years old ……………………
Over 65 Years old ……………………

32. What is the highest education level of head of household? …….. No schooling completed
…….. 1 to 8th grade
…….. 9th to 12th grade
…….. Completed high school (high school diploma, GED credential) …….. Some college
…….. Associate’s degree
…….. College degree (Bachelor’s degree)
…….. Graduate degree (Master’s, Professional school, Doctorate degree)

33. Please indicate all races and/or ethnicities of people living in your household. …….. American Indian, Alaska Native
…….. Asian or Pacific Islander
…….. Black, African American
…….. Hispanic/ Latino
…….. White, Caucasian
…….. Other, specify: ………………….
…….. Mixed race, specify: ………………….

34. What is the total income of all member(s) of your household combined? …….. Less than $35,000
…….. $35,000 to $ 49,999
…….. $50,000 to $ 74,999
…….. $75,000 to $ 99,999
…….. $100,000 to $150,000
…….. Greater than $150,000

K. End of Survey
Thank you for filling out this survey! Your data is very valuable to our understanding of indoor air quality and mechanical ventilation in new California homes.

Please return your completed survey in the envelope provided.

If you have any questions about the survey, please contact: [LBNL contact provided] IAQ in Mechanically Ventilated U.S. Homes INA-19-10-297-R2

04-April-2020 SI-48

2026-01-21 – REGULAR MEETING – REVISED ORDINANCE
REVISED LANGUAGE ADDED TO THE ORDINANCE IN RED TEXT.

ORDINANCE NO. 1055

AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF

RANCHO CUCAMONGA, CALIFORNIA, ADOPTING AN

AMENDMENT TO THE ETIWANDA HEIGHTS NEIGHBORHOOD

AND CONSERVATION PLAN IN ORDER TO ALIGN THE
SPECIFIC PLAN’S RESIDENTIAL DENSITY WITH THE GENERAL
PLAN, INCORPORATE SITE PLANS FOR PLANNING AREAS 1
AND 2 , MAKE OTHER REVISIONS TO FACILITATE

DEVELOPMENT IN ACCORDANCE WITH THE GENERAL PLAN,

AND ADD NEW BUILDING TYPES AND DEVELOPMENT

STANDARDS CONSISTENT WITH THE NEW DENSITY (DRC
2025-00022), AND MAKE OTHER CONFORMING REVISIONS,
AND ADOPTING AN ADDENDUM TO THE SPECIFIC PLAN’S

PREVIOUSLY CERTIFIED EIR

A. Recitals.

1. On November 6, 2019, the Rancho Cucamonga City Council approved Ordinance 957 to adopt the Etiwanda Heights Neighborhood and Conservation Plan (EHNCP), DRC2015-00751, as a specific plan (the “Specific Plan”), and to regulate development in the area comprising approximately 4,393 acres extending roughly from Haven Avenue easterly to the City’s boundary with Fontana, and from the northerly City limits to the San Bern ardino National Forest boundary.

2. Subsequently, on December 15, 2021, the Rancho Cucamonga City Council adopted Resolution 2021-133 to adopt a comprehensive update to the Rancho Cucamonga General Plan.

The Land Use Element of the General Plan designated the land encompassing the Specific Plan’s Neighborhood Area as “Traditional Neighborhood,” which permits a gross maximum residential development density of up to 8 dwelling units per acre.

3. The property designated as the Specific Plan’s Neighborhood Area has or will be sold by the San Bernardino County Flood Control District to a developer for future development in accordance with the Specific Plan and the General Plan.

4. The developer, The Previti Group, has applied to the City for a Specific Plan Amendment (DRC 2025-00022) for the following amendments to the Specific Plan: (1) establish the site plans for planning areas 1 and 2 of the Specific Plan , as de picted in Exhibit “A ,” attached hereto and incorporated into this Ordinance as if fully stated herein; (2) add new building types, revise building widths/heights and other measurements, revise map keys, and make other revisions to Chapter 5 of the Specific Plan, as described and depicted in Exhibit “B,” attached hereto and incorporated into this Ordinance as if fully stated herein ; and (3) make other conforming revisions to facilitate development at the proposed density to Chapters 1, 2, 3, 4, 6, and 7 of the Specific Plan, as described in Exhibit “ C,” attached hereto and incorporated into this Ordinance as if fully stated herein. The amendments to the Specific Plan shown in Exhibits “A”, “B”, and “C” are collectively referred to herein as the Specific Plan Amendment. The primary purpose of these amendments is to align the Neighborhood Area’s density with the General Plan’s designation of eight units per acre and permit development in accordance with such density.

5. The City has prepared an Addendum to the previously certified Etiwanda Heights Neighborhood and Conservation Plan (EHNCP) Draft Environmental Impact Report (EIR) (SCH# 2017111002) and the Addendum evaluated the proposed Specific Plan Amendment under the ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

EHNCP EIR. The Addendum is attached hereto in Exhibit “E,” incorporated into this Ordinance as if fully stated herein.

6. On December 10, 2025, the Planning Commission opened a duly noticed public hearing on the Specific Plan Amendment and the Addendum, and concluded the hearing on that date, and thereafter, among other actions, adopted Resolution No. 2025-045, recommending that the City Council approve the Specific Plan Amendment and the Addendum.

7. On January 21, 2026, the City Council conducted a duly noticed public hearing on the Specific Plan Amendment and Addendum and concluded the hearing on that date.

8. All legal prerequisites prior to the adoption of this Ordinance have occurred.

B. Findings.

1. Recitals. The City Council hereby specifically finds that all of the facts set forth in the Recitals, Part A, of this Ordinance are true and correct.

2. CEQA. Pursuant to the California Environmental Quality Act (“CEQA”) (Pub.

Resources Code, § 21000 et seq. ) and CEQA Guidelines, the City Council considered the Addendum, attached as Exhibit “ E”, and the previously certified EHNCP Environmental Impact Report (EIR) (SCH# 2017111002) adopted by the City Council in 2019. Consistent with CEQA Guidelines Section 15164, the City Council finds and determines that an Addendum to the EIR is the appropriate environmental document to analyze the Project because:
a. Some changes or additions to the EIR are necessary, but none of the conditions described in State CEQA Guidelines Section 15162 calling for the preparation of a subsequent EIR have occurred.
b. There are no substantial changes proposed by the Project that will require major revisions of the previously adopted EIR due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects;
c. No substantial changes have occurred with respect to the circumstances under which the Project is undertaken that will require major revisions of the previously adopted EIR due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects; and d. There is no new information of substantial importance, which was not known and could not have been known with the exercise of reasonable diligence at the time the IS/EIR was adopted showing that: (a) the changes proposed with the Project will have one or more significant effects not discussed in the EIR; (b) there are significant effects previously examined that will be substantially more severe than shown in the EIR; (c) there are mitigation measures or alternatives previously found not to feasible would in fact be feasible and would substantially reduce one or more significant effects of the project, but the City declines to adopt the mitigation measures or alternative; or (d) mitigation measures or alternatives which are considerably different from those analyzed in the EIR would substantially reduce one or more significant effects on the environment, but the City declines to adopt the mitigation measure or alternative.

ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

e. Based upon all evidence in the record, included the evidence and findings contained in the Addendum, the City Council hereby finds that the Specific Plan Amendment will not cause any new significant effects on the environment not previously analyzed in the EIR and an addendum is the appropriate level of environmental review under CEQA .

3. Findings. Based upon all available evidence presented to the City Council during the above-referenced public hearing on January 21, 2026, including written and oral staff reports, together with public testimony, the City Council hereby specifically finds as follows:
a. The Specific Plan Amendment includes (1) establishing the site plans for planning areas 1 and 2; (2) adding new building types, revising building widths/heights and other measurements, revising map keys, and other revisions; and (3) revising Chapters 1, 2, 3, 4, 6, and

7. b. The proposed Specific Plan Amendment is consistent with the General Plan goals, policies, and implementation programs. Specifically, the Specific Plan Amendment’s purpose is to align the Specific Plan’s density for the Neighborhood Area with the General Plan Land Use Element’s “Traditional Neighborhood” land use designation, which permits a gross maximum residential development density of up to 8 dwelling units per acre. The Specific Plan Amendment is intended to facilitate the development of housing in accordance with such density.

Further, the new building types outlined in Chapter 5 of the Specific Plan implement General Plan Policy LC 4.5, which promotes a range of choices on the types of housing available within the City at a variety of price points.
c. The land use and development regulations within the Specific Plan Amendment are comparable in breadth and depth to similar zoning regulations contained in Title

17. Specifically, the Specific Plan Amendment is consistent in breadth and depth with the zoning regulations developed for the Traditional Neighborhood land use designation. d. The administration and permit processes within the Specific Plan Amendment are consistent with the administration and permit processes of the zoning code. The Specific Plan Amendment does not alter the administration and permit processes of the zoning code, except that the new Neighborhood Area Transfer of Development Rights Program builds on the zoning code’s existing transfer of development rights program at Chapter 17.77 of the Municipal Code. e. Approval of the Specific Plan Amendment would not be materially injurious or detrimental to adjacent properties. The Addendum and EIR support this finding. f. The findings set forth in this Ordinance reflect the independent judgment of the City Council.

C. Ordinance.

The City Council of the City of Rancho Cucamonga does ordain as follows:

1. Adoption of Specific Plan Amendment. On the basis of the foregoing and all of the evidence in the administrative record before it, the City Council hereby adopts the Specific Plan Amendment as follows:

ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

a. Planning Areas 1 and 2 depicted in Exhibit “A” are hereby incorporated into the Specific Plan for all purposes and shall be treated as the regulating plan for phases 1 and 2 of the Specific Plan.
b. The text, tables, and images (including redlined errata text and images) depicted and described in Exhibit “B” are hereby incorporated into an appropriate place in Chapter 5 of the Specific Plan.
c. The additions and deletions to the text shown in Exhibit “C” are hereby incorporated into the appropriate places in Chapters 1, 2, 3, 4, 6, and 7 of the Specific Plan.
d. Staff is hereby directed to incorporate the following revisions to the final Specific Plan; 1) The Maximum Density for projects subject to the Transfer of Development Rights program shall be 20 units per acre ; 2) Units added to the Transfer of Development Rights bank shall expire 8 years from the date they are added to the bank; 3) The walk-up and 12 -plex building types are prohibited within Planning Area 4; 4) The Eligibility Criteria for the Transfer of Development Rights Pr ogram shall prohibit a Sending Site from being locat ed within the sloped blanks a djacent to Los Osos High School and within an y property burdened by an overhead utility easement , including the Southern California Edison utility corridor; 5) all future specific plan amendment, tentative tract map, or design review application shall require at least one neighborhood meeting prior to the application’s planning commission hearing, provided that a tentative tract map and design review application shall not require a design review committee hearing ; 6) A minimum of two building types are required in any planning area of up to 50 acres in size, a minimum of three building types are required in any planning area of between 51 acres and 80 acres in size, and a minimum of four building types are required in any planning area greater than 80 acres in size; 7) Estate House, Extra Large House, Large House, Small House, and Medium Hous e are the only building types permitted within the Neighborhood Estates Zone; and 8) The maximum height of any building type within the Specific Plan shall be 2.5 stories.

These amendments are subject to each and every condition set forth in the Conditions of Approval, attached as Exhibit “D”. The City Council directs staff to prepare a final version of the Specific Plan, inclusive of the foregoing amendments and all such text, tables, and images, and to maintain an official copy of the Specific Plan in the Planning Department.

2. Adoption of EIR Addendum. On the basis of the foregoing and all of the evidence in the administrative record before it, the City Council hereby adopts the Addendum to the EHNCP EIR attached hereto as Exhibit “ E” and the revisions to the EIR’s Mitigation Monitoring and Reporting Program contained therein. The City Council directs staff to attach the Addendum and the revised Mitigation Monitoring and Reporting Program to the EIR.

3. Severability. The City Council declares that, should any provision, section, paragraph, sentence, or word of this Ordinance be rendered or declared invalid by any final court action in a court of competent jurisdiction, or by reason of any preemptive legislation, the remaining provisions, sections, paragraphs, sentences and words of this Ordinance shall remain in full force and effect.

ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

4. Enforcement. Neither the adoption of this Ordinance nor the repeal of any other Ordinance of this City shall in any manner affect the prosecution for violations of ordinances, which violations were committed prior to the effective date hereof, nor be construed as a waiver of any penalty or the penal provisions applicable to any violation thereof.

5. Certification. The City Clerk shall certify to the adoption of this Ordinance.

___________________________________
L. Dennis Michael, Mayor
ATTEST: ___________________________________
Kim Sevy, City Clerk

I, Kim Sevy , City Clerk of the City of Rancho Cucamonga, do hereby certify that the foregoing Ordinance was introduced at a regular meeting of the City Council of the City of Rancho Cucamonga held on the _______ day of ___________, and was passed at a regular meeting of the City Council of the City of Rancho Cucamonga held on ____________, 202_, by the following vote:

AYES: COUNCILMEMBERS:

NOES: COUNCILMEMBERS:

ABSENT: COUNCILMEMBERS:

ABSTAINED: COUNCILMEMBERS:

ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

Exhibit A
Planning Areas 1 and 2
ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

Exhibit B
Chapter 5 Revisions
ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

Exhibit C
Revisions to Chapters 1, 2, 3, 4, 6, and 7
ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

Exhibit D
Conditions of Approval

ORDINANCE NO. 1055
EHNCP SPECIFIC PLAN AMENDMENT, DRC2025-00022
January 21, 2026

Exhibit E
Addendum to EHNCP EIR