Photo credit: Zorba the Geek, via Wikimedia Commons

Nearly half of the air inside a home can come from the garage and homes with attached garages also have higher indoor levels of certain air pollutants. These air pollutants include benzene, CO, and NO2. In the winter, polluted air is drawn into the home from the attached garage because of the higher pressures found in the garage.

Dr. Daniel Aubin, Team Leader of the Indoor Air Quality Group at NRC’s Construction Research Centre, spoke at the SOCAAR Seminar on November 7th about two separate interventions to reduce residential exposures to pollutants from attached garages. These findings came from a joint study conducted by Health Canada and the National Research Council Canada, which tested the effectiveness of an exhaust ventilation in the garage and an improved sealing of the garage-house interface wall.
The first intervention of installing an exhaust ventilation in the garage reduced the indoor gaseous pollutant concentrations by 23 to 61 percent. Furthermore, it was a low cost, practical method that could be installed in both new and old homes.

The second intervention of sealing the garage-home interface wall was effective at reducing the garage-to-home inter-zonal air flow by 50 percent. It also reduced the garage and home leakiness by 5.3 percent -and 9.2 percent, respectively. This sealing method was also a low cost, practical intervention that was suitable for new and old homes.

Comparing the two interventions, the sealing intervention was preferred by occupants because it costs less than the exhaust fan and uses a passive technique that doesn’t generate noise like the exhaust fan, which is continuously on. To mitigate the noise from the exhaust fan, alternative ways for modulating the exhaust fan are currently being modeled. For example, running the fan for 10 minutes every hour or for five minutes after the garage is opened or closed.

The study demonstrated the two interventions were effective in reducing air filtration from attached garages into homes, and subsequently reduced occupant exposures to harmful pollutants. Considering about 61 percent of Canadian homes have an attached garage, these interventions maybe important prescriptions to incorporate into Canada’s National Building Code.