Vented to Unvented Crawl Space

To convert a vented crawl space to an unvented crawl space, in all of the vent openings and air sealing and insulation are installed at the exterior walls instead of at the underside of the floor above. As a result, the crawl space becomes part of the conditioned space of the home. This provides a temperate space for heating and cooling equipment and ductwork located in the crawl space so it will last longer and operate more efficiently. Sealing off the vents, insulating the walls, and covering the ground with a vapor barrier that is sealed to the walls also helps to reduce potential moisture problems by keeping out humid outside air and moisture vapor from the ground. As an added benefit, the conditioned crawl space can provide climate-controlled storage space.

Checklist

This U.S. Department of Energy checklist includes important specifications that can contribute to a complete and quality installation. All work shall comply with these specifications, all relevant codes and standards, and all manufacturer installation instructions. The contractor shall check each box on the checklist below and sign and date at the bottom to certify the work is completed.

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The crawl space shall be inspected for any evidence of bulk water penetration, moisture or pest damage, and a list of any potential problems shall be provided to the homeowner before proceeding with the work so remediation can be fully addressed as necessary. The contractor shall verify proper foundation drainage and foundation waterproofing/damp-proofing before proceeding.

The contractor shall verify proper foundation drainage and foundation waterproofing/dampproofing and determine if flood vents are needed before proceeding.

If the crawlspace ground level is below the surrounding grade, perimeter drainage shall be provided.

Sufficient access shall be provided. A minimum 16x24-inch, airtight, insulated access door shall be installed in the perimeter wall. If below grade, a minimum 16x24-inch threshold is also required. Alternatively, a minimum 18x24-inch access panel shall be installed through the floor inside the home.

Any existing insulation shall be removed and any rotting wood shall be replaced. All wall surfaces shall be cleaned of any dirt or debris.

A minimum 6-mil-thick polyethylene sheeting shall be installed over the entire ground with a minimum lap of 6 to 12 inches; all seams and any tears or holes shall be taped. In addition, the polyethylene sheathing shall be extended a minimum of 6 inches up all foundation walls and concrete footings and taped to the walls or footings for a continuous seal. Note: the ground shall be cleared of all vegetation and organic material before installing the ground vapor barrier.

All sealants used shall be compatible with their intended surfaces and meet fire rating requirements around flues. Maximum gap dimensions shall be consistent with manufacturer’s specifications.

Foundation wall vents and other penetrations shall be blocked and sealed. If required, some vents may be replaced with flood vents that include weather stripping to reduce standby air infiltration.

All penetrations through the framed floor shall be sealed for fire safety in accordance with the International Residential Code. Some jurisdictions may require a non-porous sealing product.

Cripple walls, rim joists, and foundation walls shall be air sealed and insulated to an R-value that meets or exceeds the 2012 International Energy Conservation Code.

Insulation installation shall meet ignition barrier requirements.

All rim joists adjoining the exterior shall be insulated with high-density closed-cell foam sprayed directly against the rim joist or with rigid foam that is cut to fit and sealed in place with caulk or canned spray foam.

Foundation walls shall be insulated with either spray foam or rigid foam insulation.

If using spray foam, high-density closed-cell or medium-density open-cell foam shall be sprayed directly on the entire surface of all foundation walls adjoining the exterior.

If using rigid foam panels, they shall be attached to the interior of the foundation wall with construction adhesive applied in a serpentine pattern. When using two layers of foam, the seams should be staggered. These panels shall completely cover all crawlspace wall surfaces with no air gap between them and they shall be fully in contact with the masonry wall, with no gaps. Panel seams shall be fully sealed with caulk, foam, mastic, or flashing tape that is specified as acceptable by the rigid foam insulation manufacturer.

HVAC supply and return air flow to the crawl space shall be provided at a rate of 1 CFM/50 ft2 of crawl space floor area.

Water intrusion shall be monitored after the work is complete and any necessary repairs shall be made.

After completion, a combustion safety test shall be performed if any natural draft combustion equipment (e.g., water heater, furnace) exists in the crawl space to ensure there is no back-drafting or spillage of combustion emissions.

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 a target ventilation rate based on house size as follows: 50 cfm for up to 1,500 ft2, 70 cfm for 1,501 to 2,500 ft2, and 100 cfm for over 1,500 ft2. If the home has no whole-house ventilation system, or if the existing system does not meet the target ventilation rate, recommendations shall be made to the homeowner to either install a new system or repair the existing system to meet the target ventilation rate.

At the completion of the work, a radon test kit shall be provided to the homeowner with a recommendation to initiate a radon remediation strategy if post-retrofit radon measurements exceed EPA acceptable levels.

Tips to Sell Quality Installed Home Improvements

Home Improvement Expert 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:

Trust Matters: Inform homeowners how your work conforms to this world-class expert guidance. Recommend they visit the DOE website as evidence these are indeed official best practices.

Knowledge Matters: Take advantage of the Building America Solution Center as a resource for becoming an expert on these projects.

Clarity Matters: Tell prospective clients to contrast your expert-recommended best practices with other contractors.

Value Matters: Advise prospective clients to insist other bids also include these checklists to ensure equivalent quality work.

Message Matters: Showcase on your website and marketing materials that your company uses the highest quality best practices specified on HIE Checklists.

Experiences Matter: Provide visual evidence contrasting the difference between poor and high quality work such as infrared images; pre- and post-energy bills; short and long warranties; and simple charts and graphics depicting performance advantages.

Related Guides

Information guide describing things to consider when considering home retrofits in the basement or crawlspace including HVAC, wiring, or structural systems.