An attached garage is a nice place to park your car and store your stuff, but it can also be a health hazard. The simple act of starting your car in the morning produces harmful carbon monoxide; gas furnaces, water heaters, chemicals, fertilizers and paints can all generate harmful fumes. These colorless, odorless, potentially lethal gasses can silently seep into the house via cracks, holes, ductwork and improperly sealed air and vapor barriers.
Traditionally garages weren’t air-sealed for exhaust fumes, but the 2012 International Energy Conservation Code now requires air sealing between the garage and any conditioned space. That said, when it comes to air sealing, the garage still remains problematic, even when the rest of the house is done right. The High Performance Building Zone at the 2018 Internal Builder’s Show in Orlando dove into the issue, discussing proper practices and techniques for air sealing garages and crawl spaces. Here’s what you need to know:
- Where joists cross the wall between the conditioned space and the garage, install blocking in each joist bay and seal around the blocking with caulk or expanding foam. Acceptable blocking materials include plywood, OSB, and rigid insulation board.
- If the garage shares a slab with the home, use a pliable gasket to seal between the sill plate and the slab on the separation wall.
- Before installing the drywall, use expanding foam to fill gaps around any wire and plumbing penetrations in the wall or ceiling.
- When hanging drywall, use construction adhesive (tape!) to seal around the edges.
- The water heater platform is a common source of air leaks. Make sure you install and seal the drywall in that area before building the platform.
- Install foam gaskets behind outlets and switch plates, and seal the boxes to the drywall with sealant for extra protection.
- Keep ductwork out of the garage. Even a small leak could draw harmful fumes into the living space.
- When in doubt, ventilate! Installing a timer-operated passive vent from the garage to the outside can remove pollutants from the garage air and send the outdoors.
- Last, but not least, the door between the living space and the garage is a key component to the air-sealing strategy. Select an insulated, metal, fire-rated, self-closing door with an air-tight weather seal.
For a more in-depth look at air sealing attached garages, please visit Building America Solutions Center for solutions and compliance techniques.