How to Make Drywall Airtight

May 15, 2016

An air barrier stops air from leaking into exterior walls. That not only keeps heat from escaping, but it also prevents moisture from entering into stud, joist, and rafter bays where it could condense and cause hidden mold and rot.

Drywall can be an effective air barrier, but only if you are careful to stop air from moving through electrical outlets, light fixtures, and other holes that connect living space to wall and ceiling cavities. The combination of the drywall, framing, and caulk, foam, and sealant make up the air barrier assembly. Here are five areas where a little bit of extra effort during drywall installation can prevent potential leaks.

Electrical Boxes

Sealing the holes created by electrical boxes eliminates a major source of air movement into exterior walls. Because of the stack effect—the tendency of air to enter low and exit high in a building due to the difference in density between warm air and cold air—isolating fixture boxes in ceilings is even more important than in a wall.

One solution is to apply caulk or low-expansion foam where wires and fasteners penetrate the box. Or you can install EnergyBlocks (energyblock.com), foam boxes that can be sealed in place around outlets, switches, or light boxes after the wiring is in place [1A, 1B]. EnergyBlocks come in three sizes and cost between $3 and $5 each (less when purchased in quantity).

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