Mechanical ventilation and indoor air quality in recently constructed homes in cool and humid climates of the U.S.

This dataset was collected as part of the Building America Ventilation and Indoor Air Quality (BAVIAQ) field study. The BAVIAQ study aimed to measure indoor air quality (IAQ) parameters, characterize ventilation equipment and other house and household characteristics, and actions that impact IAQ, with a focus on the role of whole-house mechanical ventilation (WHMV). This dataset was obtained from visits and monitoring in 32 single-family homes constructed since 2013 in the cool and humid climate of Illinois. A total of 41 weeks of data were collected. These included one week of data collection in each home under the “as-found” condition of no WHMV, and a second week of data collection in nine homes, during which an exhaust fan was operated to provide WHMV. The dataset includes time-resolved measurements of CO2, PM2.5, formaldehyde, and radon at one or multiple indoor locations, and time-integrated samples of gravimetric PM2.5, NO2, NOx, and formaldehyde collected both indoors and outdoors. Occupants’ activities, including ventilation equipment usage, cooking, window opening, and other usage related to IAQ, were also monitored. Participants also provided household characteristics, practices influencing ventilation and pollutant sources, and self-reported satisfaction with air quality, thermal comfort, and other environmental factors. Building performance metrics were documented, including envelope and duct leakage, mechanical ventilation airflow rates, WHMV system type, controls, operational status, labeling, and compliance with ASHRAE 62.2–2010. The dataset can be used to support research on IAQ impacts of WHMV systems, building performance, occupant behavior, and pollutant exposure in recently constructed, energy-efficient homes. It enables paired-condition comparisons, facilitates evaluation of ventilation standard compliance, and provides a foundation for examining the effectiveness of WHMV in reducing indoor pollutant levels.

Methods
Overview of the data collection

The basic structure of the study was to characterize the mechanical ventilation equipment functionality in each house through observations and performance measurements, monitor ventilation equipment usage, and measure air quality parameters indoors and outdoors over weeklong periods. Data were also collected by asking occupants to provide information about the household, their practices related to ventilation and pollutant sources and controls, and their satisfaction with air quality, thermal comfort, and other environmental factors in the home. Homes were monitored for one week with their WHMV operating as-found. In a subset of homes, the WHMV was configured by the research team to meet the ASHRAE 62.2–2013 continuous ventilation requirement and monitored for a second week. Due to limitations in finding homes with operable WHMV, local exhaust fans were utilized to meet ASHRAE 62.2.

Each study home was visited by a two-person field team at the start and end of each monitoring period. House and ventilation equipment characterization typically occurred during the first visit and included documenting the system configuration and as-found operational status. Observational data collected during the field team visits included ventilation equipment model numbers, filter ratings, filter location, type of cooking appliance, and other details. During this visit, the field team installed instrumentation to measure indoor and outdoor air quality parameters, operation of ventilation equipment, and the central forced air (CFA) system, use of the main cooking appliance, and the open-closed position of selected doors and windows. Two-week homes were visited between the weeks to collect and redeploy passive samplers, download data from some instruments, and change the WHMV equipment to meet ASHRAE 62.2. Air leakage of the building envelope and air distribution ducts of the CFA heating and cooling system typically occurred during the final visit. The team also asked the participant if they thought their home had a WHMV system and, if so, did they knew how to operate it.

Participants were asked to partake in normal household activities, with the exception that windows and doors should not be used for natural ventilation, and no smoking of any kind should be done inside the home during the data collection period. Participants were asked to complete an activity log for each day of the monitoring period, designed to record actual occupancy as well as routine and intermittent activities that could affect IAQ.

The study was reviewed and approved by the Central Institutional Review Board (IRB) of the U.S. Department of Energy.

Eligibility and recruitment

The study aimed to collect data in a sample of otherwise similar newly constructed single-family detached or attached homes being monitored with their WHMV in its as-found condition, and a subgroup of homes being monitored for a second week with their WHMV operating at the ASHRAE 62.2 2013 continuous ventilation requirement. The minimum eligibility criteria were that the home had to be constructed in 2013 or later and completed at least one year before data collection to reduce the potential impact of all materials in the home being very new (and potentially still in an initially higher emitting regime for formaldehyde) and occupants being too recently introduced to the house and its ventilation equipment. The goal was to study homes that were built to recent standards and with relatively new equipment.

The main outreach method for recruitment was through semi-regular advertisements on the University of Illinois Urbana-Champaign’s faculty and staff weekly e-newsletter. A phone interview was conducted to screen homes for eligibility. To participate, they must have been newly constructed (2013 or later), single-family detached or attached homes, located in Illinois, be owner-occupied, and non-smoking. If a home was eligible, questions about the building characteristics and ventilation systems were asked over the phone. Participants were instructed that they would need to avoid opening exterior doors and windows during the monitoring period. All homes would participate for a minimum of one week with the WHMV system left in its current operating state (as-is). A subset of homes that had a venting range hood and multiple bathroom exhaust fans, of which the airflows could meet the ASHRAE 62.2-2013 continuous ventilation requirement, were invited to participate in an additional week of monitoring. During the second week, the bathroom exhaust fans were operated to meet the 62.2 airflow requirement, and the participants were informed not to modify them during the remaining monitoring period.

Additional recruitment was done through mail postcards in the Champaign and Urbana areas. Eligible homes were identified using a mix of local online data sources, including building permits (https://data.ccrpc.org/dataset/building-permits), property tax records (https://champaignil.devnetwedge.com/), and real-estate websites. Word of mouth from existing participants enrolled in the study also played a role in recruiting new homes.

Measuring and monitoring airflows and air leakage

Airflows were measured for WHMV systems, bathroom and kitchen exhaust fans, and clothes dryers. To determine inputs and coefficients for the natural infiltration model, a Delta-Q test was conducted in each home to measure building envelope and duct leakage, and to determine envelope leakage flow coefficient (c) and exponent (n).

Forced air heating and cooling system operation was monitored by deploying anemometers and TRH sensors at supply air registers. Exhaust fans were monitored by anemometers or motor on/off loggers. Cooking appliance usage was monitored by temperature sensors on the cooktop surface. Patio door, garage to house door, and main bedroom door status were recorded. Portable air cleaners, humidifiers, and other devices related to IAQ were monitored by plug load power meters.

Air quality measurements

Air quality measurements were conducted at both on-site outdoor and indoor locations. The devices used in this study for indoor and outdoor air quality measurements and their accuracy, deployment location are shown below.

Measurement Device
Parameters
Accuracy(a)
Res.
Sampling locations

Met OneE-Sampler
Estimated PM2.5 by photometry; 
Photometry: ± 10% to the gravimetric method, typical when K-factored to local particulate type (b).
5min 
Outdoor

Met One BT-645 Photometer
Estimated PM2.5 by photometry
±5% traceable standard with 0.6 µm PSL, autozeroing function enabled to check baseline hourly(c)
1 min
Indoor central

AirVisual Pro
Estimated PM2.5 by photometry, CO2, T, RH
CO2: ±50ppm or 2% of reading(d)
10 sec–5min
Indoor central; Master BR; Office, secondary bedroom, or family room

Ogawa Passive Samplers
NO2 and NOx
Based on field validation(e): 7 d relative deviation of 3±2% NO2 at 11-37 ppb; 4±3% NOX at 16-85 ppb; 10±9% (NOX-NO2) at 4-56 ppb
1 wk
Outdoor; indoor central

Graywolf FM-801
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 wk
Outdoor; Indoor

Onset HOBO UX100-003,
T, RH
±0.21 °C from 0 to 50 °C
1 min
Outdoor, Indoor: master bedroom, master and secondary bathroom (U23); Laundry room (UX100-011); Central location, attic, basement (UX100-003);

RadStar RS300
Radonshort-termrm
<10% deviation from 0.5 to 150 pCi/L
60 min
Indoor: central and/or basement

AccuStar Alpha Track
Radon, long-term
General within ±15% to ±30% when deployed in the field for periods ≥3 months
3–6 months
Indoor: central and/or basement

PEM Sampler
PM2.5 by gravimetric mass
Balance accuracy: 0.1µg
1 wk
Indoor

a. Based on manufacturer specifications unless otherwise noted.

b. We did not evaluate the K-factor for the device; thus, outdoor PM concentrations measured by MetOne need to be compared with local monitors and gravimetric mass results before using them for analysis

c. Cross checks between the indoor and outdoor MetOne units in the previous study showed close agreement. Therefore, no adjustment was applied to the indoor MetOne data in this dataset.

d. Co-location between AVP units found a good correlation in CO2 measurements.

e. Based on field validation in California reported by Singer et al. 2004.

f. The collected mass on a filter was determined as the difference in post and pre-exposure weights, and air concentrations were calculated using the sample volume calculated by the elapsed exposure time and sample airflow. See Quality Assurance sections for details

Participant survey and daily activity log

Before the field team visited the homes, participants were provided with and asked to respond to an online questionnaire that asked how they feel about their home environment and about the factors that can affect their IAQ. They were also asked about activities and product use and for information related to the home and household, including basic demographic and health-related questions. During the first visit, the field team provided participants with a printed activity log for each day of the monitoring period, designed to capture actual occupancy and routine and intermittent activities that could affect IAQ. This included prolonged opening of windows and doors, house cleaning, cooking, and burning candles. The log also had the occupant report periods of poor outdoor air quality, for example, from a nearby forest fire.

Acknowledgements

ICRT performed this work under contract to the Illinois Applied Research Institute, University of Illinois Urbana-Champaign (UIUC). ICRT moved from UIUC to the Champaign County Regional Planning Commission in July 2023. We acknowledge the contributions of former ICRT staff members J.S. (field work and instrumentation management) and S.G. (project management), who left before this date. We thank the residents who welcomed us into their homes during this project, and for working with us during the early days of the pandemic when home visits were more challenging to execute. We thank the UIUC School of Architecture and its students for producing floor plans at each site and the following for their contributions. E.W., co-conceived of the study, arranged funding, and managed the Building America program through which the study was implemented; L.B. helped administer the study for the Building America program; and both provided helpful input throughout the study development and data collection phases. R.M. program director for the Residential Energy Services Network, queried the rated homes database and provided records to assist with participant recruitment. Y.W. and A. J. helped to develop the dataset.