Exterior EPS Foam
Bobmarlon1
| Posted in Green Building Techniques on
Hi
I have started building a house with standard 2×6 construction and roxull batts. Now that the project is under way I have decided I would like to add an exterior foam layer to the house so we don’t lose any interior space. I would probably use EPS as I can get it custom manufactured nearby in custom shapes and thickness. The thing I am most confused about is air sealing with this method. If I am not to have an interior vapour barrier how do I go about air sealing the walls and attic. Any Detail would be appreciated.
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Replies
Bob,
Q. "If I am not to have an interior vapor barrier, how do I go about air sealing the walls and attic?"
A. I think you are confusing vapor barriers and air barriers. If you live somewhere where it's common for builders to install interior polyethylene, you may be under the misapprehension that the interior polyethylene is your air barrier. It almost always isn't.
Typically, energy-conscious builders establish the primary air barrier at the exterior sheathing. If you have OSB sheathing, you'll need to tape the seams of the OSB. One approach is to use OSB sheathing manufactured by Huber (Zip sheathing), and to seal the seams with Zip System tape.
A good air barrier also requires attention to penetrations and transitions (for example, the transition from the wall air barrier to the ceiling air barrier). For more information, see these articles:
"Questions and Answers About Air Barriers"
"Air Sealing an Attic"
"Air-Sealing a Basement"
"A Practical Air-Sealing Sequence"