Air sealing of the suspended floor over a crawlspace mainly consists of sealing all penetrations and large holes with appropriate materials like spray foam, sealant, wood, and gypsum board. See the Guide on Air Sealing Considerations for Accessible Attic Ceiling Spaces. In most cases, the subfloor and flooring acts as the main air barrier and vapour retarder, separating the conditioned space from the crawlspace. Insulating the joists can be challenging if there are services and lateral bracing in the joist space. It is important to install the insulation with a snug fit around all crawlspace obstructions.

This air sealing and insulating procedure is for floors above vented crawlspaces.