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

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. Homes were monitored for one or two weeks, operating with or without WHMV, or under both conditions (two-week homes, n = 11). Measurements included envelope and duct airtightness; mechanical ventilation airflows; time-resolved CO₂, PM_2.5, formaldehyde, and radon; and time-integrated gravimetric PM_2.5, NO₂, NOₓ, and formaldehyde. Participants reported on ventilation use, IAQ-related activities and perceptions. Major deficiencies were observed in WHMV installation, operation, and occupant awareness. Thirty-seven homes had controlled WHMV equipment. Twenty-one could meet the ASHRAE 62.2–2010 airflow requirement with continuous or controlled runtime, but only 11 systems were operating at the field team’s arrival (as-found condition). Performance and homeowner awareness varied by system type. Most energy recovery ventilators and ventilating dehumidifiers were functional and operating as found, with owners aware of their purpose. Fifteen homes had exhaust fans with compliant airflow and sound ratings but no labeling, and owners did consider them WHMV. Central Fan integrated supply (CFIS) systems were rarely functional. Six homes had no kitchen exhaust ventilation, and only 35 had airflow above the 50 L/s requirement of 62.2–2010 at any setting. PM_2.5 concentrations were low in most homes. WHMV operation did not discernibly lower PM_2.5 or formaldehyde but did significantly reduce CO₂ and radon in both two-week homes and all homes with/out WHMV. Occupants of homes with WHMV operating as found felt they had better control of temperature and relative humidity.