When a CleanSpace® system is installed, you want to seal vents to keep out evil unconditioned outside air. But vents aren’t the only way outside air can get into your crawl space. Spaces under the sill plate and around pipes and wires to the outside, poorly fitting or rotted hatch doors, and other odd openings are all paths that need to be sealed to get the best results.

One area that was previously ignored is the open cavities in the top of block walls. Block walls are most common in dirt crawl spaces. Outside air goes right through porous block walls and up out of the top of the wall into the inside of the crawl space. To seal the top of the block walls, a product called "CleanSpace® Wall Cap" works great. It’s an "L"-shaped molding that slips right on top of the block wall covering the space the sill plate does not. The clear plastic allows for termite inspections without removing it.