In planning stage of building house. Will have plans and blueprints drawn up soon. I have read that the latest thinking on the foundation (we will have crawlspace 3-4 ft high) is to go ventless for better moisture protection. I'm getting a lot of negative responses on this idea. What do the pros think? I want to build as energy efficiently as possible. Thanks!

The crawl space can only be ventless if it is conditioned (continuously operated mechanical ventilation, 1 CFM per 50 square feet of floor area, with a vapor retarder covering the ground surface, or supplied with conditioned air and the perimeter walls are insulated, plus the vapor retarder), unless the Virginia building code differs from the versions I use (NY ans PA).

Richard, So in other words I have to have some sort of fan installed in order to keep the air moving or go to a conventional vented foundation?

Yes. A sealed unventilated crawl space is not permitted under present code.

The most energy-efficient crawl space would seem to be a conventional well-ventilated space with good floor insulation.

PS: I should have said "insulation in the floor above".

This message has been edited. Last edited by: Richard Hetzel,