I wanted to start this blog by explaining a method of hanging drywall that can make a building more energy efficient. It is easy for a drywall contractor to become more involved in the building performance mania. Myron R. Ferguson
It turns out that one way to create a more energy efficient building is to have a good air barrier at the thermal boundary (building envelope). The building envelope separates the conditioned (heated or cooled spaces) from unconditioned spaces (outdoors, attics, and the ground). The building envelope is quite often right where the drywall is installed.
Why do we want to stop air from entering walls and ceilings? To prevent wasting energy. If heated or cooled air is allowed
to escape through gaps and holes in the building envelope then energy is being wasted. Also escaping air can carry moisture that could condense in walls or attics which then can cause mold and rot.
To create a good air barrier, the drywall has to be attached to the framing in an airtight manner and all possible air leakage points around holes cut into the drywall have to be properly sealed. The combination of the drywall, framing, caulks, and sealants make up the air barrier assembly.A sheet of drywall as a material is a good air barrier. But as you know it is not very often that a piece of drywall is hung that is not cut full of holes (electrical boxes, ductwork windows and doors and etc.) .
Holes in drywall on exterior wall for oulets & swithces
Before the drywall is hung some sealing of electrical boxes and similar protrusions will have to be done. Some simple caulking and sealing of holes in the boxes is an easy way to seal but for a much tighter seal isolating the boxes is a better idea. Foam or clay products can be used to form an airtight cover around the box.When the drywall is attached and cut around the opening, the potential leakage point is sealed with adhesive or caulk.
Energy Block around electrical box
Isolating protrusions in ceilings is even more important than in a wall because of the stack effect in a building . The stack effect refers to the draft established in a building from air entering low and exiting high.
Insulated boxes for can recessed lights in attic. Applying foam to seal gaps before covering with drywall.
Drywall adhesive is quite often used when attaching drywall to help eliminate fastener pops. Drywall adhesive can be used to air seal all edges of the panels. If instead of just applying the adhesive along the center of the panels the adhesive is also applied along the perimeter of each wall and also around the framing of window and door openings. A flexible caulking or an acoustical sealant would be a better choice because of the flexing and stretching characteristics, but I know for most drywall contactors the adhesive would be their first choice because of the convenience. Just make sure the bead is continuance and about a 3/8-inch thick bead.
Because of the way ceilings are constructed it is difficult to seal the perimeter of the drywall with adhesive or caulking. If the walls are properly sealed around the perimeter then air should not be able to find its way along the ceiling edges. But because I believe in being extra thorough I suggest sealing the perimeter of the ceiling. Where walls and ceilings intersect expanding foam can be used to seal in gaps. This can be done from up above in the unconditioned attic or from below after the ceiling is hung but before the walls are butted up to the ceilings.
Air sealed ceiling edges in attic- scarp drywall was used in conjunction with the foam
We all need to be more energy conscious, and yes it does take extra time and attention to detail to properly air seal a building. By helping the customer understand the concept it really is a win -win situation. The key point is that the architect, owner, builder, and hopefully with the help of a certified green verifier all need to work together. The process can be very easy and rewarding for a long time.