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Are we creating issues in single-family homes as we seal attic leaks and push the neutral pressure plane closer to the ground?

I just read Joe Lstiburek's article BSI-075: How Do Buildings Stack Up? and started wondering - are we creating issues in single-family homes as we seal attic leaks and push the neutral pressure plane closer to the ground?

Are problems - like the MURB problems Joe highlighted in his article - showing up in residential single family homes? By that I mean, is moisture - that used to leave via attic leaks - now being pushed out through upper exterior walls and lifting the paint off stucco or causing mould growth? As utilities, like the one I work for, promote air sealing do we need to educate crews doing the work on how much is too much? Or are there mitigation strategies that we should be employing?

Asked by Gary Hamer
Posted Mon, 03/17/2014 - 18:52
Edited Tue, 03/18/2014 - 04:59

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Gary,
First, a confession: I didn't know what a MURB was until I looked it up. (If there are other confused GBA readers, a MURB is evidently a multi-unit residential building.)

If your question is, "Can limited air sealing in a building cause unexpected problems?" the answer is, "Of course."

Weatherization contractors need to be alert to all of the different ways that building systems interact. This is called the "house as a system" approach. (For more on this issue, see The House as a System.)

You are apparently also asking whether exfiltrating air can cause moisture problems in walls. The answer is yes, although other sources of moisture are typically more common in buildings with wet wall problems. For more information on this issue, see All About Wall Rot.

These facts do not imply, as you suggest, that those who "promote air sealing ... need to educate crews doing the work on how much is too much." There really aren't any benefits to deliberately making our buildings leaky, or deliberately leaving known holes in our building envelope instead of sealing them.

Weatherization experts have been performing air sealing work for at least 35 years. The best weatherization contractors know how to proceed. They know where the biggest holes are; they know where start air sealing; they know how to verify their work with a blower door and an infrared camera; they know how to perform combustion safety tests; they know when radon testing is in order; and they know when it is important to recommend the installation of a mechanical ventilation system.

If you take a "house as a system" approach, and use well-trained weatherization contractors, you'll have more success than just leaving your buildings deliberately leaky.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 03/18/2014 - 05:20
Edited Tue, 03/18/2014 - 05:22.

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