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Should I cover my crawlspace floor with thick mil plastic too?

pizza's picture


I plan on encapsulating and closing off the two vents in my crawlspace according to the latest methods for doing so. One of which (recommended by Martin Holladay, Energy Vanguard website, not sure of his last name spelling) is insulating the rim joists, insulating the walls with rigid foam panels, then covering everything with thick plastic sheeting. My crawlspace is only 3 ft high or so and thankfully the floor is poured concrete throughout. Do I need to also place plastic on the floor? I live in southeastern PA. I also plan on adding a dehumidifer.The crawlspace connects to my unfinished basement which also has a dehumidifier.

The Cliff Notes versions of the three options in this situation are:

1) One is to close off the vents, insulate, and add a dehumidifier.

2) The other option is to close off the vents, insulate and provide some conditioned air and install a floor register.

 3) Mechanically vent the crawlspace with a small fan rated for the square footage of the crawlspace in cfm.

I'm choosing the first option.

To repeat my question, do I need to put plastic down on the poured concrete floor too?

Thanks in advance.

Plastic on the concrete (post #215568, reply #1 of 1)

Plastic on the concrete floor? Only if there is non beneath the concrete. Do a test. Clean and lay a piece of plastic on the floor. Tape off the edges. Wait a day or two. Peel off. If the area is darker, there is moisture in the concrete. There are various ways to seal concrete without applying a layer of plastic.  

Think about radon gas too. In your haste to slay one monster, you may inadvertently be facing consequences from another. Just saying (and I am not a radon expert).

Mel Fros