BASC Search | Building America Solution Center

Rigid foam insulating sheathing installed over an existing garage ceiling with retrofits to air seal exterior wall before adding exterior wall insulating sheathing

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Right – Closed-cell spray foam insulation in the shared wall between the garage and living space helps to air-seal the wall and protect occupants from garage pollutants.

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Compartmentalization uses air sealing to reduce the stack effect in a multistory building - the large vertical pressure difference in a tall building is separated into smaller pressure differences at each floor

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Fire-rated sealants or a fire-rated assembly air seal the tops and bottoms of the demising walls that separate one dwelling unit from another ina multifamily building

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A continuous bead of sealant is installed to air seal along the top and bottom plates at all exterior walls and intersecting interior walls as well as around windows in exterior walls

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Right - Comprehensive air sealing of the walls includes caulking of the subfloor-sill plate seams and corner seams, taping of electrical boxes, and spray foaming around pipe penetrations.

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Form an insulation dam of sheet metal around a flue pipe in the attic after air sealing around the pipe with sheet metal and fire-rated caulk or canned foam

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Retrofit of cantilevered wall with beam showing details at the outside corner for installing air sealing and rigid foam insulation plus water control membrane in the wall and overhanging floor

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When using I-joists, make sure to fill in the gaps on each side of the blocking material to air-seal the joist bay where a wall separates conditioned and unconditioned spaces.

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This aerosol sealant process seals off small leaks in the building envelope with tiny particles of nontoxic acrylic sealant that are sprayed into the air while the home is pressurized with a blower door kit.

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If spray foam is used to air seal over backer rod around the window’s rough opening, foam should entirely cover the rod and let dry then trimmed flush to frame

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Right – This supply duct is thoroughly sealed at all joints with mastic to prevent air leakage and the duct is equipped with a damper to provide zoned heating and cooling along with other trunk ducts.

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The builder installed this OSB under the roof rafters and air sealed the seams with tape then added a dropped drywall ceiling to provide a service cavity for ducts and wiring, while minimizing holes into the attic.

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Once window trim is removed around window, any fibrous insulation is removed and the opening is brushed before installing canned foam or backer rod and caulk to air seal the rough openings

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Before installing drywall, contractors install two beads of a sprayer-applied elastomeric sealant along framing and top plates to forma a flexible, air-tight seal between the framing and dry wall.

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Wrong – Where possible, design walls and specify window sizes and placement to minimize the use of studs around windows; and seal all wood-to-wood seams to minimize air leakage through walls.

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A sill gasket is installed under the two layers of fire-rated gypsum providing air sealing at the foundation slab in this 2-hour fire wall separating two units in a multifamily row house building

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The dark purple areas and long streaks in this IR camera image show extreme cold spots along the top of the walls, indicating a lack of both air sealing and insulation above the top plates of these walls.

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Form an insulation dam of heat-resistant insulation with at least 3 inches of clearance around a flue pipe in the attic after air sealing around the pipe with sheet metal and fire-rated caulk or canned foam

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Right - Reduce condensation risks to blanket insulation by installing perforated vapor retarder covered fiberglass blankets over rigid foam that is air-sealed at all edges; staple the blanket to nailers and top/bottom plates and tape over the seams.

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Right – The window header is filled with spray foam and sealant is used to air seal wood-to-wood seams; however, it would be preferable to design the wall to avoid so many stacked studs around the windows because they prevent wall insulation installation.

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Sealed Attics?

Reference

Article describing how insulating and air sealing unfinished attic spaces can lead to reduced energy bills in some homes.

Wrong - Hole in duct is not sealed and duct joint to subfloor is not sealed.

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Why Seal and Insulate?

Reference

Introductory guide to air sealing the envelope of a home to reduce wasted energy and save on energy costs.

Sealed and Insulated Flex Ducts

Video

Video describing how to seal and insulate flex ducts.

Connection in place but not sealed

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Mechanically fastened and sealed

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Aerosol Envelope Sealing of New Residences

Reference

Technical report describing the research behind a new aerosol-based sealing method, utilizing pressurization and a dispersed sealant fog, facilitated by a standard blower door, to automatically measure, locate, and seal air leaks in new homes in the United States, providing an efficient solution to...

Aerosol Envelope Sealing of Existing Residences

Reference

Report examining the effectiveness of an aerosolized acrylic technique for air sealing existing homes to reduce air leakage and improve energy efficiency.