Raising a small building to spray-foam on subfloor


Old 10-08-08, 01:09 PM
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Join Date: Feb 2007
Location: SouthEast Louisiana
Posts: 324
Question Raising a small building to spray-foam on subfloor

I just had a 12' x 24' building built to start a business in. I'm calling this my new GREEN office cause I'm trying to go as energy and environmentally friendly as possible. I'm getting an 11.4 EER rated A/C and I have radiant barrier on the ceiling. The building is sealed very well from what I can tell and how I saw them build it, but I have decided on spray-foam for the walls, possibly the ceiling over the radiant barrier too, and the subfloor.

The subfloor is about 6 - 8 inches off the ground and the base frame is galvanized steel leaving about a 2 inch gap between it and the ground. The air space between the ground and floor is my concern (moisture). Having that a/c running in there all the time I'm sure will cause moisture on the bottom of the 5 ply - plywood interlocking lipped floor.

How do I raise or tilt the building so that I can spray-foam on the underside of the floor?

Do ya'll think just putting weather sealing (Thompson brand) clear paint on it will be enough? or should I do the foam?
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Old 10-09-08, 09:51 AM
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Join Date: Jul 2008
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I would do a couple of things.

First, Do not spray foam over a radiant barrier. By definition radiant heat only passes through a gas or a vacuum. If you spray the radiant barrier with foam, you eliminate the "air gap" required to make it work. In fact, you will actually increase the conductive heat flow through the roof since you now have a "solid". I would spray the attic floor or go ahead and kill the radiant barrier and foam it and do a sealed, non-vented attic with no insulation on the ceiling sheetrock.

Second, I would consider "sealing" the crawlspace. Use a closed cell spray foam. Here are the details: http://www.buildingscience.com/docum...9d-crawlspaces You don't have a large crawlspace, but the concept is good.

Last edited by SwanaSwana; 10-09-08 at 09:54 AM. Reason: Better Info.

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