Long term air quality monitoring in a net-zero energy residence designed with low emitting interior products

Abstract

The National Institute of Standards and Technology (NIST) constructed a Net Zero Energy Residential Test Facility (NZERTF) to support the development and adoption of cost-effective Net Zero Energy (NZE) designs and technologies. One key design objective was to provide for occupant health and comfort through adequate ventilation and reduced indoor contaminant sources. To improve source control, guidelines were implemented to utilize products with relatively low volatile organic compound (VOC) emissions. Indoor and outdoor concentrations of formaldehyde and 30 other VOCs were measured approximately monthly during the first year of house operation. Indoor temperature and ventilation conditions were relatively constant over the study. Indoor minus outdoor (I–O) concentrations of many VOCs varied with outdoor temperature. Correlation analyses of I–O concentrations versus inverse outdoor temperature (1/K) suggested that some building envelope components were an indoor source of aldehydes (but not formaldehyde) and several other VOCs. Floor area specific emission rates were calculated and compared to values from several prior studies of conventional new houses. The average formaldehyde emission factor of 6.7 μg h−1 m−2 in this study was lower than literature values (29 μg h−1 m−2 to 45 μg h−1 m−2) indicating formaldehyde source control approaches were effective. VOC measurements at other indoor conditions demonstrated that eliminating mechanical ventilation contributed more to an increase in indoor VOC concentrations than an 8 °C increase in the indoor temperature.