Stopping air leaks is the single most important part of making a house more energy efficient. You can stop air on the outside with plywood, housewrap, and tape, but the best air barrier is a system that incorporates the whole wall or roof assembly.
As it turns out, drywall is excellent at stopping air. If you doubt that, try to blow through it. The weak spots are the seams between sheets and the holes that you have to cut for windows, doors, electrical boxes, and can lights. The process for installing drywall as an air barrier is called the airtight-drywall approach (see “Energy-Smart Details” in FHB #214 and online at FineHomebuilding.com), and it relies on caulks, sealants, canned foam, and gaskets to seal the weak spots.
The first step to airtight drywall is to identify what building scientists call the thermal boundary—insulation to us regular folks. The air barrier needs to be continuous along the thermal boundary. This is especially important where interior walls join exterior walls at rim joists or in places where chases are run for plumbing or electrical work.
We decided to hang drywall in the garage shop in FHB’s Project House using the airtight approach, partly to show you how to do it and partly so that the editors could make me do their dirty work. The outside of the house eventually will be covered with housewrap and rigid-foam sheathing. The drywall, therefore, is not the primary air barrier but is the interior part of an air-barrier system.
Materials you’ll need
To seal up this garage shop, I used flexible caulk, construction adhesive, and cans of expanding foam. Various types of gaskets are also often used in airtight-drywall jobs. The most basic material, of course, is drywall. To…