Air and Pollutant Transport from Attached Garages to Residential Living Spaces - Literature Review and Field Tests

The National Institute of Standards and Technology (NIST) is conducting a study on the indoor air quality (IAQ) impacts and engineering solutions related to the transport of pollutants from attached garages to residential living spaces. Natural or fan-induced pressure differences across air leakage paths in house-garage (HG) interfaces can result in the transport of the contaminants generated in garages into adjacent living spaces. This paper summarises a literature review on the transport of pollutants from garages to residential living spaces and describes a field study to estimate the range of airtightness of attached garages and of HG interfaces in the United States. Although the body of literature on pollutant transport from attached garages to residential buildings is limited, the studies reviewed provide substantial evidence that transport of contaminants from garages has the potential to negatively impact residential IAQ in either an acute (e.g., carbon monoxide from automobiles) or chronic manner (e.g., storage of chemical products). However, the literature contains few answers on issues such as the airtightness and geometry of the HG interface, the impact of heating and cooling equipment in the garage, and the effectiveness of potential engineering solutions. To address one gap in understanding these issues, the airtightness of garages and HG interfaces was measured in five residences using fan pressurisation. While the small sample of houses limits generalisation of the results, a range of house ages, styles, and sizes was included. For all homes tested, the garage was found to be at least twice as leaky as the house, based on air change per hour at 50 Pa. The leakiness of the garage envelope, based on surface area normalised effective leakage area at 4 Pa (ELA4/SA), ranges from a high of nearly eleven times to a low of two and a half times that of the house exterior envelope leakage. On average, the HG interface was almost two and a half times as leaky as the rest of the house envelope, when based on ELA4/SA. However, this average is somewhat skewed due to one HG interface measured in this study that is almost eleven times as leaky as the rest of the house envelope. Conversely, a larger Canadian study found HG interfaces to be comparable to house envelopes but found the average garage to be about ten times as leaky as houses possibly because Canadian houses are consistently tighter than U.S. houses (Fugler et al. 2002). The knowledge gained from this review and the field study will be used in a simulation study of the potential occupant exposure to pollutants from attached garages and to explore potential engineering solutions to this IAQ problem.