Insulation, Radiant and Vapor Barriers - floor joist insulation

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shimp
03-16-08, 11:20 PM
if i insulate floor joists in crawl space with the vapor barrier up against the heated side, can i put 6 mil plastic on bottom of joists to hold insulation in place and to be a vapor barrier?

d00bs
03-17-08, 12:38 AM
No, you would have a double vapor retarder. Use the push rod wires to hold up the insulation. The poly goes on the floor of the crawl lapped up the sides and all seams taped/sealed. Depending on your crawl you might have better results insulating the walls of the crawl and not the joists at all with 2 inch pink foamboard instead, with the same poly on the floor.