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Community and Q&A

Air tightness & testing?

user-1137156 | Posted in PassivHaus on

The common method of expressing test results of air tightness tests is air changes per hour. @ 50 pascals. How is the building volume calculated? Does it include exterior wall volume (use outside dimensions)? Does it include an unheated basement? or crawlspace? In testing are vents for ventilation systems (HRV.ERV) capped? Are dryer or range vents capped? What is “state of the art” air tightness? What are best known test results?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Jerry,
    I suggest you read these two articles:

    Blower Door Basics

    How Much Air Leakage in Your Home Is Too Much?

    Most of the time, dimensions are taken on the exterior of the house -- because that's easiest to measure. The volume includes the basement or a conditioned crawl space, but not a vented crawl space.

    Ventilation system intake or exhaust vents (and passive air inlets) are sometimes (but not always) sealed, depending on the aims of the blower-door test.

    If you can achieve a Passivhaus level of airtightness (0.6 ach50), you're doing very well. Many Passivhaus builders have done much better than that; for example, Chris Corson tested his Maine Passivhaus at 0.286 ach50. I'm sure a few builders have done even better.

    However, here's a caveat: many blower-door results mentioned on the Web -- especially those that seem unlikely -- are erroneously reported. It's fairly common for confused builders to move the decimal point from where it belongs, so all blower door results on the Web should be taken with a grain of salt.

  2. user-1137156 | | #2

    Martin, Thank you! Especially for the articles.

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