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Air Sealing, Insulating, and Venting Attics and Roofs to Reduce Heat Gain

Information Guide

Information guide providing links to guides describing specific ways to air-seal, insulate, and ventilate attics and roofs to minimize heat gain in new and existing homes.

CAD image for roof pipe penetration water and air sealing details

CAD File

Examples of many common ceiling penetrations that will be difficult to insulate and air seal in this cathedral ceiling.

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Provide flashing and sealing integrated with the air and water control layers for vents and other roof penetrations

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All holes through the top plates should be sealed with canned spray foam to prevent conditioned air from leaking into the attic.

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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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A dormer with an openable window (not shown) can provide access to the roof if flood waters rise too high and too quickly; the dormer should be properly insulated, flashed, and air sealed

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Wrong – This roof membrane on a low slope roof is fluttering and may fail because it is not fully adhered and deck seams below are not sealed, allowing air to leak up into the assembly while the membrane is pulled up due to negative pressures from wind

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Roof Eaves Sealed with Self-Adhering Membrane in Cold Climates

Guide

Guide describing how to apply self-adhered asphaltic membranes at eaves in cold climates to help guard against ice dams.

Vented Attic vs Unvented Cathedral Attic Air Flow

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Right – This low-slope flat roof assembly has continuity of both the air and water barriers

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Right – This low-slope roof and parapet assembly has continuity of both the air and water barriers

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

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Right - Spray foam insulation has been sprayed onto the underside of the sloped roof and the gable end wall to provide a sealed, insulated attic for housing the HVAC ducts

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Unvented Insulated Sloped Roofs

Guide

Guide describing construction of unvented, sloped, insulated roof assemblies in high wind zone areas.

Home Energy Guide - Techniques, Tactics, and Tips: Ice Dams

Reference

Article describing the causes that form ice dams, as well as solutions for preventing future ice dams on roofs, focusing on air sealing to prevent hot air leakage.

The thermal boundary for a gable roof can be located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

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A low-sloped shed roof with the thermal boundary located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

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A 1- and ½-story home with a room located in the attic and the thermal boundary located at either a) the walls and ceiling of the attic room with small vented attic spaces or b) the roof line for an unvented attic

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Air Sealing, Insulating, and Venting Attics and Roofs to Reduce Heat Gain

CAD image for roof pipe penetration water and air sealing details

Examples of many common ceiling penetrations that will be difficult to insulate and air seal in this cathedral ceiling.

Provide flashing and sealing integrated with the air and water control layers for vents and other roof penetrations

All holes through the top plates should be sealed with canned spray foam to prevent conditioned air from leaking into the attic.

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

A dormer with an openable window (not shown) can provide access to the roof if flood waters rise too high and too quickly; the dormer should be properly insulated, flashed, and air sealed

Wrong – This roof membrane on a low slope roof is fluttering and may fail because it is not fully adhered and deck seams below are not sealed, allowing air to leak up into the assembly while the membrane is pulled up due to negative pressures from wind

Roof Eaves Sealed with Self-Adhering Membrane in Cold Climates

Vented Attic vs Unvented Cathedral Attic Air Flow

Right – This low-slope flat roof assembly has continuity of both the air and water barriers

Right – This low-slope roof and parapet assembly has continuity of both the air and water barriers

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

Right - Spray foam insulation has been sprayed onto the underside of the sloped roof and the gable end wall to provide a sealed, insulated attic for housing the HVAC ducts

Unvented Insulated Sloped Roofs

Home Energy Guide - Techniques, Tactics, and Tips: Ice Dams

The thermal boundary for a gable roof can be located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

A low-sloped shed roof with the thermal boundary located at either a) the flat ceiling with a vented attic or b) the roof line for an unvented attic

A 1- and ½-story home with a room located in the attic and the thermal boundary located at either a) the walls and ceiling of the attic room with small vented attic spaces or b) the roof line for an unvented attic

Construct Roofs and Attics for Ice Dam Prevention

Attic Ventilation Fans

Integrated Truss House - How to install inset windows

Cold Climate Building Techniques and Concepts: Vapor retarder

Low-Slope ("Flat") Roofs

Condensation Control in Attics and Roofs in Cold Weather

Attic Eave Minimum Insulation

Cold Climate Building Techniques and Concepts: Cathedral Roofs

De-Icing Ice Dams, BSI-097

Attic or Roof? An Evaluation of Two Advanced Weatherization Packages, BA-1205

Roof Escape Openings for Flood-Prone Areas