Building design and operational choices that impact indoor exposures to outdoor particulate matter inside residences

Abstract

Much of human exposure to particles of outdoor origin often occurs inside homes where we spend most of our time. This work (1) reviews existing literature on the important parameters governing the infiltration and persistence of particles of outdoor origin in residences, (2) re-analyzes portions of data from recent experimental investigations of submicron particle infiltration and central HVAC system operation in single-family homes, and (3) combines these data to highlight particularly stark differences in particle infiltration factors and human exposures to submicron particles of outdoor origin that are driven by building envelope design, filter choice, and HVAC system design and operation (with an additional focus on data from one low-energy home). Results reveal that envelope design and construction, HVAC filter selection, and HVAC system operation can lead to variations in infiltration factors for submicron particles ranging by a factor of 60 or more from the most protective homes to the least protective homes. Moreover, an additional experiment performed in the most protective low-energy home (when relying on infiltration for ventilation air) was also responsible for the highest amount of outdoor particle infiltration when tested again while using an energy recovery ventilator connected to an outdoor air supply for ventilation air, suggesting that residential mechanical ventilation systems can adversely influence outdoor particle infiltration if improperly installed.