Heat gain through the roof or attic is about 15-25% of the heat gain for the entire building (ORNL 2022). This heat gain can be reduced by using “cool” white or reflective roofing materials as described in the guide Cool Roofs and Walls, by using a radiant barrier as described in the guide Attic Radiant Barriers, by providing shading as described in the guide Landscaping to Reduce Cooling Load, and by adequately air sealing, insulating, and venting the attic. There are several guides in the Solution Center that describe effective ways to air seal, insulate, and ventilate attics in new and existing homes.
Attic Air Sealing
Guides describing ways to air seal attics and ceilings in new homes include the following guides for the whole attic and specific components within the attic or penetrations through the attic floor:
Air Sealing and Insulating Ceilings
Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck
Dropped Ceiling/Soffit Below Unconditioned Attic
Air Sealing Drywall to Top Plate
Insulating and Air Sealing Existing Non-ICAT Recessed Lights
Air Sealing Attic Access Panels/Doors/Stairs
Air Sealing Duct and Flue Shafts
Air Sealing Bathroom and Kitchen Exhaust Fans
Sealing Duct Boots to Floor or Drywall
Air Sealing Plumbing and Piping
Air Sealing Doors Adjacent to Unconditioned Space
Construct Roofs and Attics for Ice Dam Prevention
Guides for air sealing attics and components within the attic in existing homes as a retrofit measure include the following:
Spray Foam Insulation Applied to Existing Attic Floor
Insulating and Air Sealing Existing Floors above Unconditioned Spaces
Roof/Attic to Exterior Wall Air Control Upgrade
Air Seal Top Plates or Blocking Missing at Top of Walls Adjoining Unconditioned Spaces
Air Sealing Recessed Light Fixtures Below Unconditioned Space
Attic Insulation
Guides for insulating attics in new homes include the following:
Air Sealing and Insulating Ceilings
Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck
Unvented Insulated Sloped Roofs
Insulation Installation Achieves RESNET Grade 1
Condensation Control in Attics and Roofs in Cold Weather
Insulation Below Attic Platforms
Ducts Buried in Attic Insulation and Encapsulated
Guides for insulating attics in existing homes as a retrofit measure include the following:
Batt Insulation for Existing Vented Attics
Blown Insulation for Existing Vented Attic
Above-Deck Rigid Foam Insulation for Existing Roofs
Water Managed Roof – Re-roofing and Adding Insulation Over a Sloped Roof
Water Managed Roof – Re-roofing and Adding Insulation over a Flat Roof
Spray Foam Insulation Applied to Existing Attic Floor
Below Deck Spray Foam Insulation for Existing Roofs
Attic Ventilation
Guides describing ways to ventilate attics and roofs include the following:
Calculating Attic Passive Ventilation
Condensation Control in Attics and Roofs in Cold Weather
Attic Air Sealing, Insulating, and Ventilating for Ice Dam Prevention
More Info
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The following authors and organizations contributed to the content in this Guide.
Pacific Northwest National Laboratory