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Does using Knauf Ecoseal allow the house to breathe?

I live in Alberta, Canada, and am building a new house. The builder introduced me to the Ecoseal product which sounds great. As my knowledge on construction is limited, I have a question. If there is Ecoseal applied and batting along with a vapour barrier, can the wall still breathe to eliminate moisture, thus not having mold concerns 5 years down the road like open-cell foams?

Asked by Ash Bryks
Posted Tue, 01/07/2014 - 00:11
Edited Tue, 01/07/2014 - 06:55


2 Answers

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I'm not sure what you mean when you ask, "Can the wall still breathe?" There is no technical meaning to the word "breathe" or "breathable."

Some people think that a "breathable" wall leaks air. Other people think that a "breathable" wall is vapor-permeable.

If you want your wall to leak air, don't install Knauf EcoSeal. EcoSeal is designed to seal air leaks. For more information on EcoSeal, see Air Sealing With Sprayable Caulk.

I should point out, however, that it would be stupid to build a leaky wall on purpose. Sealing air leaks is a good thing to do.

EcoSeal is a water-based latex caulk. It is somewhat permeable to water vapor; its permeance will vary depending on its thickness. However, its vapor permeance is irrelevant, because it isn't installed as a complete layer -- only in thin bands to cover cracks. The permeance of your wall sheathing -- not the permeance of the EcoSeal -- will determine whether or not your wall assembly dries to the exterior.

Finally, products that are vapor-permeable aren't always better than products that are vapor-impermeable. In the case of open-cell spray foam, which you mention, there are roofs that are rotting because open-cell spray foam was chosen instead of closed-cell spray foam (a vapor-impermeable choice). For more information on this issue, see Open-Cell Spray Foam and Damp Roof Sheathing.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 01/07/2014 - 09:49

Helpful? 0

Excellant response Martin. You nailed it!

Answered by Chris Brown
Posted Tue, 01/07/2014 - 10:53

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