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Attic Air Sealing and Insulation

Done correctly, attic air sealing and insulation can reduce utility costs while improving comfort, indoor air quality, and durability.

The attic shall be inspected for water leaks and moisture, structural, or pest damage. A list of all needed repairs shall be provided to the homeowner before attic work begins so remediation can be fully addressed as necessary.
The attic shall be inspected for sufficient attic ventilation (e.g., ridge vent, soffit vent). Ventilation issues shall be addressed before proceeding with attic air sealing or insulation.
If there is active knob and tube wiring present in the attic, insulation shall not be installed until wiring is replaced or properly boxed. Work shall not proceed if existing insulation is vermiculite, which may contain asbestos.
All exhaust fans shall be modified as required to vent to the outside, not into the attic.
A combustion safety test shall be performed if any natural draft combustion equipment exists in the home to ensure there no backdrafting or spillage. Any combustion safety issues shall be addressed before proceeding with attic work.
The contractor shall state whether existing insulation is to be removed or moved aside for air sealing.
Attic Air Sealing and Air Barriers Prior to Insulation
All gaps, cracks, seams, and penetrations between conditioned and unconditioned space (such as gaps around lighting fixtures, HVAC duct boots, electric wiring, plumbing pipes, and flues) shall be sealed with sealants alone (e.g., caulk, foam, aerosol sealant) if the gaps are narrow enough or with rigid blocking material sealed in place with sealants, per the sealant manufacturer’s instructions. Fibrous insulation is not an air barrier and shall not be used for air sealing.
The seams where drywall attaches to the top plate at all interior and exterior walls shall be sealed from the attic side with a caulk, spray foam, or sprayer-applied sealant.
Larger gaps and openings (such as uncovered dropped soffits and openings under knee walls or at the tops of balloon-framed gable walls) shall be closed off using a solid material such as rigid foam or OSB that is sealed at the edges with caulk, sealant, or mastic.
Gaps around masonry chimneys or gas appliance vents shall be sealed with high-temperature-rated caulk or foam and insulation dams shall be constructed around them as needed using heat-safe materials in accordance with building code requirements.
Attic access panels, doors, and drop-down stairs shall be insulated with a minimum of R-10 rigid foam insulation and gasketed (not caulked) to provide a continuous air seal when closed.
All non-ICAT recessed light fixtures shall be boxed with a solid material such as drywall or rigid foam, that is sealed at all seams with a sealant such as caulk, mastic, or spray foam.
Before installing fibrous attic floor insulation, baffles shall be installed at all attic eaves adjoining vented soffits to prevent air flow through the insulation and to provide a path for ventilation air from the soffit vents to the ridge vents. The baffles shall extend at least 6 inches above the height of the attic insulation.
Attic Insulation
Continuous R-19 insulation shall be installed at attic knee walls, skylight shaft walls, vertical portions of all dropped ceilings, and any other vertical wall adjoining conditioned space. All joints, cracks, and penetrations in the wall air barrier shall be fully sealed with caulk, foam, or equivalent.
Attic insulation shall be installed at all flat and sloped surfaces adjoining the conditioned space with less than 2% gaps, voids, and compressions and at levels that meet or exceed prescriptive levels specified by the 2012 International Energy Conservation Code. All attic insulation shall be uniform and conform to manufacturer-specified density with attic rulers to verify full depth.
After completion, a combustion safety test shall be performed if any natural draft combustion equipment exists in the home to ensure there is no backdrafting or spillage.
The home shall be inspected for the presence of a whole-house ventilation system. If one is present, the actual air flow shall be tested and verified to meet ASHRAE 62.2 -2013 capacity. Recommendations shall be made to the homeowner for either installing a new ASHRAE 62.2-2013-compliant system if one is not present, or repairing an existing system to be ASHRAE 62.2-2013-compliant if airflow is not adequate.
In U.S. Environmental Protection Agency Radon Zone 1 a radon test kit shall be provided to the homeowner at completion of the work.

BASC Guides

Information guide describing how to assess attics, ceilings and roofs before proceeding with upgrades in existing homes.

Guide describing how to air seal attic access panels, doors, and stairs to provide a continuous air barrier at the ceiling.

Guide providing information about constructing a roof with full insulation at the eaves, and insulating eaves in existing homes.

Guide describing methods for insulating an unvented attic along the roof line.

Guide describing how to increase insulation in existing homes by installing batt insulation on the ceiling plane of a vented attic.

This guides describes how to insulate and air seal attic knee walls and floor joist cavities under knee walls.

Tips to Sell Quality Installed Home Improvements

Home Improvement Expert (HIE) is a valuable tool for organizations committed to quality installed work. The following tips help optimize the value of this tool when selling home improvements:

  • Be the Expert: Take advantage of Building America Solution Center comprehensive guidance on ‘Existing Home’ retrofits.
  • Earn Trust: Inform homeowners how your work conforms to U.S. Department of Energy (DOE) world-class expert guidance and recommend homeowners visit the DOE website as evidence these are indeed official best practices.
  • Clarity with Contrast: Tell prospective homeowner clients to compare your expert recommended best practices with other contractors.
  • Ensure Equivalent Pricing: Tell prospective homeowner clients to insist other bids also include DOE checklists to ensure equivalent quality work.
  • Translate Value: Note your company uses DOE HIE Checklists based on world-class expert recommendations for home improvements on all your public-facing communication including websites, advertising, and signage.
  • Create Emotional Experiences: Provide visual evidence contrasting the difference between poor and high quality work such as infrared images for good and bad insulation and air sealing; pre- and post-energy bills following quality installed work; short and long warranties for standard and high-efficiency equipment; and charts showing amounts of contaminants in homes that can be reduced with effective fresh air systems.

Attic Air Sealing and Insulation Background

Attic Air Sealing Insulation

In older homes, attics may have extensive holes, cracks, and missing air barriers and insufficient insulation that allow unwanted heat loss in cold weather, heat gain in hot weather, and infiltration of contaminants year-round. Air sealing uncontrolled leaks and adding insulation between the attic and the home is one of the most cost-effective measures to improve your home’s performance. It can reduce your heating and cooling bills, improve comfort with less drafts, keep contaminants such as moisture, dust, and pests from entering your home, and reduce moisture-related durability problems.