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

Description

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 new and existing homes.

 

After all holes through the ceiling are air sealed and the baffles have been installed, the insulation can be installed
Figure 1. Thorough attic air sealing, insulation, and venting can help keep solar heat gain that comes through the roof from overheating the home (Source: PNNL).

 

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

Attic Knee Walls

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

Air Sealing Electrical Wiring

Sealing Duct Boots to Floor or Drywall

Air Sealing Plumbing and Piping

Air Sealing Doors Adjacent to Unconditioned Space

Air Sealing Light Tubes

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 Attic Insulation

Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck

Unvented Insulated Sloped Roofs

Attic Eave Minimum Insulation

Insulation Installation Achieves RESNET Grade 1

Attic Radiant Barriers

Condensation Control in Attics and Roofs in Cold Weather

Attic Knee Walls

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:

Roof Vents

Vented vs Unvented Attic

Calculating Attic Passive Ventilation

Condensation Control in Attics and Roofs in Cold Weather

Attic Air Sealing, Insulating, and Ventilating for Ice Dam Prevention

Construct Roofs and Attics for Ice Dam Prevention

Wind Washing

Attic Ventilation Fans

Whole-House Fans

More Info

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References and Resources*
*For non-dated media, such as websites, the date listed is the date accessed.
Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Pacific Northwest National Laboratory

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