Ventilation and Measured IAQ in new US homes

As newer homes are being built tighter than the existing housing stock, questions have been raised about the
concentrations of pollutants of concern in new homes and how mechanical ventilation systems can address this
issue. This study measured pollutants of concern in 70 new homes with mechanical ventilation in California, USA
and compared the results to a previous study of home without mechanical ventilation. The key pollutants were
measured using both time-integrated and time-resolved over a one-week period and included formaldehyde,
PM2.5 and NO2. Each home was tested for air flows of mechanical systems, together with house envelope and
forced air heating and cooling duct leakage. The results show that the homes complied with dwelling unit
ventilation fan flows and most of the time with kitchen and bathroom requirements. The measured pollutant
concentrations were almost all within acceptable limits and showed that the installed ventilation flow rates (that
complied with California building standard and ASHRAE 62.2 requirements) provided acceptable indoor air
quality. The mechanically ventilated homes had more consistent ventilation, resulting in less extreme pollutant
concentrations. However, there remain issues with system operation, e.g., poor labeling of easily accessible
controls led to three-quarters of the dwelling unit ventilation systems being turned off when homes were first
visited for this study. This paper summarizes the results of the diagnostic testing and time-integrated field
measurements, together with implications for ventilation standards.