If you took a poll of building envelope and construction forensic experts, it's likely that moisture barriers would be high on the list of most poorly understood products used in wall assemblies.

Dear Pat: I am having a house built partially on a slab and on a crawl space. Is it necessary to install a vapor barrier under the concrete, and is this something I can do myself to save some money? - ...

Question: I am having a house built partially on a slab and on a crawl space. Is it necessary to install a vapor barrier under the concrete, and is this something I can do myself to save some money?