Research Program Area: Health & Exposure
Topic Areas: Indoor Air Quality
California's building code requires mechanical ventilation to manage indoor-generated pollutants in the state's airtight, energy efficient homes. Yet outdoor air also contains pollutants at levels that can be hazardous. This study evaluated eight combinations of ventilation and air cleaning systems for pollutant removal and energy use. Systems were installed in an unoccupied 2006 house located 250 m downwind of I-80 in Sacramento. Systems were evaluated for reduction of outdoor particles (6 nm to 2.5 µm and black carbon) in summer and fall/winter, ozone and VOCs in summer, and indoor particles generated by a scripted cooking procedure. Energy use of the systems was estimated for year-round operation in varied California climates. Results demonstrate substantial benefits of high efficiency filtration at reducing air pollutant exposures, but with varying energy costs. Higher performance MERV16 filtration on supply ventilation reduced outdoor particles by 97-98% with low energy consumption, but provided no benefits for indoor-generated particles. Similarly rated (MERV13 to MERV16) filtration on the central forced air system reduced outdoor PM2.5 by 90-97% when operated at least 20 min each hour or continuously at low-speed. Air cleaning on recirculating systems also reduced indoor-emitted pollutants. The energy required to operate central systems for filtration varies. Year-round operation of a system with an efficient blower motor will use about 600 kWh/year of extra site energy. These energy costs can be reduced with a smart ventilation and filtration system that modulates with occupancy. Exhaust ventilation pulling outdoor air through the envelope (the reference system) yielded indoor PM2.5 levels that were 70% lower than outdoors. Supply ventilation with a MERV13-rated filter resulted in less protection than the Reference, indicating a need for high performance filtration when using supply ventilation.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
Stay involved, sign up with CARB's Research Email Distribution List