BASC Search | Building America Solution Center

A simple vented attic with good air-sealing of the drywall ceiling air barrier, air flow from soffit vents to ridge vents protected by ventilation baffles, and lots of insulation covering the attic floor is unlikely to encourage ice dams.

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Right-- IR photo shows how effectively spray foam insulated/air sealed attic kneewall and the floor cavities under kneewall

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The polyethylene ceiling vapor barrier is sealed to form an air barrier around the exhaust fan in this very cold climate location (≥ CZ 6).

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Wrap the air-sealed chimney with mineral wool insulation to prevent contact with the warm brick when attic insulation is re-installed around the chimney

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Right - These attic knee walls are insulated with rigid foam and sealed with spray foam to form a continuous air barrier at the gable end of this cathedral ceiling.

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Right - A technician applies a thin layer of closed-cell foam to air-seal an unvented attic assembly before filling the ceiling joists with batt or blown insulation.

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Vented roof assembly at eave retrofitted with rigid foam, spray foam, and fully adhered membrane to air seal the top of wall-to-roof transition

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Seal the drywall to top-plate seams and the lower edge of baffles to the top plate to prevent the air coming from soffit vents from flowing under baffles into insulation.

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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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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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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- This flue pipe has been air sealed with sheet metal and fire-rated caulk and an insulation dam has been constructed to keep insulation from touching the hot flue pipe

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Right – Spray foam air seals and insulates the walls including the walls behind the fireplace and covers the underside of the roof deck of this mixed-dry climate home to provide an insulated attic space for HVAC ducts.

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A floor cavity between the first and second floor can provide a conditioned space for HVAC ducts if the rim joists are insulated and air sealed, if sufficient space is available, and if open-web floor joists are used

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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.

Raised ceiling chase sealed with drywall mud

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Seal all drywall-to-top plate seams and penetrations at the attic floor

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Adhesive caulk is used to seal seams and attach the multiple layers of rigid insulation

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Roof/Attic to Exterior Wall Air Control Upgrade

Guide

Guide describing how to retrofit an exterior wall and/or attic to provide continuous air sealing.

New Code Options for Insulating, Sealing, and Controlling Moisture in Unvented Attics in Residential Buildings

Presentation

Webinar explaining new code options for insulating, sealing, and controlling moisture in unvented attics in residential buildings.

Right – The top plate-to-dry wall seams of the interior walls are sealed from the attic.

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The missing top plate in a kneewall was covered with lumber and rigid foam insulation and then sealed with spray foam

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Vented Attic vs Unvented Cathedral Attic Air Flow

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Technology Solutions Case Study: Complete and Fully Aligned Air Barrier

Case Study

Case study describing the elimination of excessive humidity in the attic of a multi-floor, single-family home that was causing condensation and water damage along the roof and eaves.

Your Northern Home: Attics/Air leakage/Stack effect

Video

Video from Cold Climate Housing Research Center on how warm air typically leaks out of homes through attics via the stack effect and how to mitigate these effects through building practices.