Designs That Work

Air Sealing / Air Drywall Approach Details

A tight building enclosure is necessary to control the movement of air in and out of building assemblies. This is important for energy conservation, thermal comfort and building durability. Moisture laden air moving into wall or roof assemblies (particularly from the exterior during cooling in hot-humid climates or from the interior during heating in cold climates) may lead to condensation and result in deterioration of moisture sensitive materials. An air flow retarder can be installed on the interior or the exterior side of the envelope or on both sides. For more detailed discussion on air flow retarders, click here.

Controlling air movement through the building enclosure requires sealing both the "big" holes and the "little" holes. The big holes occur behind bath tubs and showers on exterior walls, behind fireplaces, and where soffits or utility walls (double wall with chase) meet exterior walls or ceilings. Recessed lights collectively can be a really big hole in the ceiling assembly. These big holes are responsible for wasted energy (high utility bills), frozen pipes and condensation that can cause mold and wood decay. These big holes are easy to seal during the framing stage but only when someone has the responsibility for making sure it gets done.

The small holes occur between framing members (such as band joist to sill plate), around electrical boxes and where plumbing or wiring penetrate the envelope. The Air Drywall Approach uses the gypsum board to provide an interior air flow retarder. The gypsum board is sealed to the framing members at the perimeter of exterior walls and around penetrations such as doors, windows, and attic hatches. The gypsum board is also sealed to electrical boxes on exterior walls. Air cannot move through the gypsum board and the taped corners. Details of air sealing and the ADA are illustrated below. Photographs of many of these details are also shown in the file of photos attached to each Designs that Work climate design.

Air Sealing Details

Click on detail for expanded view.

Exterior Air Flow Retarder using Stucco		Interior Air Flow Retarder using Drywall & Framing
Interior Air Flow Retarder Using Poly Note: Only recommended for very cold climates.		Exterior Air Flow Retarder using Exterior Sheathing
Exterior AFR using Building Paper or Housewrap		Intersection of Interior Partition Wall & Exterior Wall
Intersection of Interior Wall and Insulated Ceiling		Intersection of Floor Joists and Exterior Wall
Intersection Interior Partitions		Window Jamb with Wood Trim
Window Jamb with Drywall Returns		Rim Joist / Band Joist Closure
Floor Truss Rim Closure		Set-back Rim Joist
Band Brace / Floor Truss Closure		Cantilevered Floors
Alternative Cantilevered Floors		Floor Over Garage
Shed Roof		Set-back Roof
Tub Framing		Tub Framing - Plan
Tub Framing - Interior Elevation		Fireplace Section
Fireplace - Plan View		Flue Closure
Alternative Flue Closure		Interior Soffit
Interior Soffit Constructed After Gypsum Board Installed		Dropped Ceiling
Interior soffit Constructed Before Gypsum Board Installed		Utility Chase
Split Level		Attic Access
Stairs at Exterior wall or Garage Wall