Air Sealing Materials
Use a combination of these different air sealing materials.
- Caulk: Seals gaps of less than ½". Select grade (interior, exterior, high temperature) based on application.
- Spray foam: Fills large cracks and small holes. It can be messy; consider new latex-based foams. DO NOT USE near flammable applications (e.g., flue vents). DO NOT USE expanding types on windows and doors.
- Backer rod: Closed-cell foam or rope caulk. Press into crack or gap with screwdriver or putty knife. Often used with caulk around window and rough door openings.
- Gaskets: Apply under the bottom plate before an exterior wall is raised or use to seal drywall to framing instead of caulk or adhesive.
- Housewrap: Installed over the exterior sheathing. Must be sealed with housewrap tape or caulk to form an airtight seal. Resists water but is not a vapor barrier.
- Sheet goods (plywood, drywall, rigid foam insulation): These materials form the air barrier. Air leaks only at unsealed seams or penetrations.
- Sheet metal: Used with high-temperature caulk for sealing high-temperature components, such as flues and chimneys, to framing.
- Polyethylene plastic: This inexpensive material for air sealing also stops vapor diffusion. All edges and penetrations must be sealed entirely for an effective air barrier. Poly is fragile, and proper placement is climate specific.
- Weatherstripping: Used to seal moveable components, such as doors, windows, and attic accesses.
- Mastic: Seals air handlers and all duct connections and joints.
- UL181 or foil-faced tape: Temporarily seals the air handler.
Air Sealing Checklist
- Seal bottom plate of exterior walls with caulk or gasket; seal inside edge with caulk after walls are up.
- Seal band joist with caulk, spray foam, or gasketing between the top plate and band joist, and between band joist and subfloor.
- For bathtubs on outside walls, insulate the exterior wall and air seal behind tub with sheet goods or plastic before the tub is installed. After the drain is installed, seal the tub drain penetration with sheet goods and caulk or spray foam.
- For dropped ceilings or soffits, duct and flue chases, and open partition walls use sheet goods and sealant to stop air leakage from the attic into the soffit and then insulate. Alternately, install framing and drywall for the soffits after the taped ceiling drywall is installed.
- Caulk the backsides of window flanges to the sheathing during installation.
- Use caulk to seal between door thresholds and subflooring with caulk.
- Seal window and exterior door rough openings with backer rod and caulk, or use non-expanding latex-based spray foams that will not pinch jambs or void window warranties.
- Seal all electrical wire, plumbing, and HVAC penetrations between any conditioned and unconditioned spaces with caulk or spray foam.
- Seal wiring and knockouts in electrical boxes with caulk. Also, seal outdoor mounted boxes to the exterior sheathing.
- Seal drywall to top and bottom plates using gaskets, adhesive, or caulk.
- Seal electrical switch, outlet, and circuit breaker boxes to drywall with caulk or foam.
- Seal the light fixture boxes, medicine cabinets, and bath and kitchen ventilation fans to drywall with caulk or foam for larger openings.
- Seal all duct boots to floor or drywall with caulk, foam, or mastic.
- Seal any plumbing or electrical wire penetration through drywall with caulk or foam.
- Seal gaps at whole house fan with spray foam or housewrap tape (ensure louvers function properly).
- For attic hatches and kneewall access doors, weatherstrip and include a tight latch. Add rigid insulation.
- For attic pull-down stairs, make stairs airtight using latch bolts and weatherstripping. Add an insulated cover.
- The seal between a masonry chimney and the attic framing using sheet metal or other noncombustible sheet goods and high-temperature (450°F), fire-rated caulk.
- Seal around the metal flue of combustion equipment using a UL-approved metal collar and high-temperature (450°F), fire-rated caulk.
- Use only UL-approved airtight, IC-rated recessed light fixtures (that meet ASTM E283 requirements); seal between fixture and drywall with caulk.
AIR SEAL EXTERIOR
- Repair any damaged sheathing pieces.
- Seal all exterior penetrations, such as porch light fixtures, phone, security, cable, and electric service holes, with caulk or spray foam.
- If not using housewrap, seal all sheathing seams with housewrap tape or caulk.