Most builders know the importance of keeping an intact fire barrier between the garage and living spaces. But as Matt Risinger describes in this video, there are some very important reasons for creating a tight air barrier between these spaces, as well. Beyond the fact that most garages are unconditioned and effectively "outside," a toxic cocktail of fumes coming from the garage can get sucked into the house, creating significant indoor air-quality concerns. Not least among these poisons is carbon monoxide (CO), which in the best of circumstances is released only momentarily as a car drives in or starts up. In the worst of cases, however, the release of CO into the garage can be a sustained event that turns fatal when sucked into the house

A recent report in the New York Times, "Deadly Convenience: Keyless Cars and Their Carbon Monoxide Toll" examined the not-uncommon incidences of car owners leaving cars running in the garage, tragically resulting in the deaths of occupants. The Times article points blame at car makers that don't make it sufficiently obvious to drivers that keyless-ignition cars have been shut-off. Certainly that's a tremendous fault. But there may be an equally strong argument to be made that builders who do an inadequate job air sealing the garage wall, and fail to keep the garage outside the building envelope, may share some responsibility for those CO fatalities. That's not meant as an accusation as much as it is a wake-up call signaling what's potentially at stake by not sealing the garage wall. In this context, the details Matt describes in this video bear an even closer look.