When assessing whether to air seal crawlspace and basement floors, and what air sealing method to use, the floor make up and frequency of use should be considered. Many crawlspaces have dirt, bedrock or gravel floors which should be covered completely. If the crawlspace is used frequently it may compromise the air seal. Slab-on-grade floors are easier to air seal since only cracks and penetrations in the concrete need to be sealed.

The Procedure section provides several options on how to air seal a slab-on-grade floor. It is recommended that a vapour retarder be used to reduce the humidity level in the space. This can be achieved with polyethylene sheets. If the space is frequently accessed, a more durable alternative is to apply an epoxy concrete sealer to the floor.