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

This study is part of the Building American Ventilation and Indoor Air Quality (BAVIAQ) field study. This study examines whole-house mechanical ventilation (WHMV) and indoor air quality (IAQ) in 51 single-family homes constructed since 2013 in the humid southeastern U.S in Florida, South Carolina, and Georgia. A total of 67 weeks of data were collected from homes monitored over one or two weeks, with whole-house mechanical ventilation (WHMV) systems either operated or not. Eleven homes were monitored under both WHMV conditions. The dataset includes time-resolved measurements of CO₂, PM2.5, formaldehyde, and radon; and time-integrated measurements of gravimetric PM2.5, NO₂, NOₓ, and formaldehyde. Occupants’ activities, including ventilation equipment usage, cooking, window opening, and other usage related to IAQ, were also monitored. Participants were asked to provide the household characteristics, 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. Building envelope and duct leakage, and mechanical ventilation airflows were measured. WHMV system type, control, labeling, operational status, and ASHRAE 62.2–2010 compliance were documented. The dataset supports research on IAQ impacts of WHMV systems, building performance gaps, occupant behavior, and pollutant exposure in energy-efficient residential buildings. It enables paired comparisons under controlled conditions and provides a foundation for evaluating compliance with ventilation standards and their effects on 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. Most homes were monitored for one week with WHMV equipment operating or not operating (with some adjustment or activation by the field team required in many of the homes). In a subset of homes, monitoring occurred for two weeklong periods: one with WHMV set to operate and one with WHMV not operating. 

Each study home was visited by a two-person field team at the start and end of each monitoring period. Ventilation equipment characterization typically occurred during the first visit and included documenting the system configuration and as-found operational status. During this visit the field team installed instrumentation to measure indoor and outdoor air quality parameters, operation of ventilation equipment and the 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 reset the WHMV equipment to the alternate condition. House characterization typically occurred during the final visit and included measuring air leakage of the building envelope air distribution ducts of the central forced air (CFA) heating and cooling system. Observational data collected during the field team visits included ventilation equipment model numbers, filter ratings, filter location, type of cooking appliance and other details. The team also asked the participant if they thought their home had a WHMV system and if so, did they know 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.

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 were monitored by deploying anemometers and TRH sensors at supply air registers. 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 and other devices related to IAQ were monitored by plug load power meters.

Air quality measurements
Air quality measurements were conducted at both onsite outdoor and indoor locations. The devices used in this study for indoor and outdoor air quality measurements and their accuracy, deploy locations are shown below

Measurement Device
Parameters
Accuracy^(a)^
Res.
Sampling locations

Met One ES-642 Photometer
Estimated PM2.5 by photometry
±5% traceable standard with 0.6 µm PSL, autozeroing function enabled to check baseline hourly^(b)^
1 min
Outdoor

Met One BT-645 Photometer
Estimated PM~2.5 ~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 UX100-011
T, RH
±0.21 °C from 0 to 50 °C
1 min
Outdoor (U23); Indoor central (UX100-011);

RadStar RS300
Radon, short term
<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 month
Indoor: central and/or basement

PEM Sampler
PM~2.5 ~by gravimetric mass
Balance accuracy: 0.1µg
1 wk
Outdoor; Indoor

a. Based on manufacturer specifications unless otherwise noted.

b. Outdoor PM concentrations measured by MetOne showed close agreement with nearby regulatory monitors. See Quality Assurance sections for details.

c. Cross checks between the indoor and outdoor MetOne units showed close agreement. Therefore, no adjustment was applied to the indoor MetOne data. See Quality Assurance sections for details.

d. Co-location between AVP units found good correlation in CO2 measurements, see Quality Assurance sections for details.

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
Prior to the field team visit to 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.