ARB Research Seminar
This page updated March 2, 2016
Reducing In-Home Exposure to Air Pollution
Brett C. Singer, Ph.D., Staff Scientist, Energy Analysis and Environmental Impacts Division, Lawrence Berkeley National Laboratory
March 24, 2016
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA
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, including fine particulate matter (PM₂.₅) and ozone. With the objective of informing new home designs and future versions of the building code, this study evaluated eight combinations of ventilation and air cleaning systems for pollutant removal and energy use. Systems included supply, exhaust, and balanced ventilation; filtration on the ventilation supply or on the recirculating forced air heating and cooling system; filters with varying performance ratings for fine particles; and three air cleaning technologies for volatile organic compounds (VOCs). We selected filters based on the Minimum Efficiency Reporting Value, or "MERV" scale, using the following: MERV4, MERV8, MERV13 and MERV16 in addition to including a HEPA filter in one system. All system components were installed in an unoccupied 2006 house located 250 m downwind of I-80 in Sacramento, then evaluated for their effectiveness at reducing outdoor particles (6 nm to 2.5 μm in diameter 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.
Several systems showed the potential to dramatically reduce in-home exposures to outdoor particles and ozone, with varying energy costs. High performance, MERV16-rated filtration on a supply ventilation system reduced outdoor PM₂.₅ 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 heating and cooling system reduced outdoor PM₂.₅ by 90-97% when operated at least 20 minutes each hour or continuously at low-speed. Filtration on recirculating systems also greatly reduced indoor-emitted pollutants. The Reference system, with exhaust ventilation pulling outdoor air through the moderately airtight envelope, 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.
The VOC assessment was limited by low concentrations of outdoor VOCs (~15 μg/m³ total VOC concentration, TVOC). Indoor VOCs concentrations were substantially higher, around 300 μg/m³ TVOC, with formaldehyde being the predominant species. All three systems with VOC removal technology achieved modest VOC improvements over the Reference system.
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.
Brett C. Singer, Ph.D., is a Staff Scientist and the Indoor Environment Group Leader in the Energy Analysis and Environmental Impacts Division and a Principal Investigator in the Whole Building Systems Department at Lawrence Berkeley National Laboratory (LBNL). Dr. Singer conceives and leads research projects related to air pollutant sources, physical-chemical processes, and pollutant exposures in both outdoor and indoor environments, aiming to understand these systems for the purpose of developing effective control strategies. The recent focus of Dr. Singer's work has been indoor environmental quality and risk reduction in high performance homes. This work has the goal of accelerating adoption of IAQ, comfort, durability, sustainability, and resilience measures into new home construction and retrofit practices. Key focus areas of this work are low-energy systems for filtration, smart ventilation and mitigation approaches to indoor pollutant sources including cooking. Dr. Singer co-developed the population impact assessment modelling framework (PIAMF). He holds a Ph.D. in Civil & Environmental Engineering from the University of California, Berkeley.