Volatile organic compound concentrations and emission rates in new manufactured and site-built houses

Concentrations of 54 volatile organic compounds (VOCs) and ventilation rate s were measured in four new manufactured houses over 2-9.5 months following installation and in seven new site-built houses 1-2 months after completio n. The houses were in four projects located in hot-humid and mixed-humid cl imates. They were finished and operational, but unoccupied. Ventilation rates ranged from 0.14-0.78 h(-1). Several of the site-built ho uses had ventilation rates below the ASHRAE recommended value. In both manu factured and site-built houses, the predominant airborne compounds were alp ha-pinene, formaldehyde, hexanal, and acetic acid. Formaldehyde concentrati ons were below or near 50 ppb with a geometric mean value for all houses of 40 ppb. Similarities in the types of VOCs and in VOC concentrations indica ted that indoor air quality in the houses was impacted by the same or simil ar sources. Major identified sources included plywood flooring, latex paint and sheet vinyl flooring. One site-built house was operated at ventilation rates of 0.14 and 0.32 h(-1). VOC emission rates calculated at the two con ditions agreed within +/-10% for the most volatile compounds. Generally, th e ratios of emission rates at the low and high ventilation rates decreased with decreasing compound volatility. Changes in VOC emission rates in the m anufactured houses over 2-9.5 months after installation varied by compound. Only several compounds showed a consistent decrease in emission rate over this period.