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Community and Q&A

Blower door procedure standards?

daylandry | Posted in General Questions on

We just completed our blower door test done after framing and prior to insulation of our new home under construction in Zone 4c Southern Oregon and had fantastic results: With the Panasonic Whisper Green fans taped off it was 83 cfm @63Pascal (.23 ACH63). We couldn’t get a reading at 50 pascal. Unbelievably tight. When we uncovered the bath & kitchen fans it jumped to 172 cfm @50 (.48 ach50). Still meets Passive House standard, but more leakage than is necessary. For some reason the built-in back-draft dampers for the Panasonic fans are designed to not completely close ( they are cup shaped and not round). You could easily feel the cold air pull past your hand during the test.
My question is: What is the standard for this test, bath and kitchen fans open or taped off? Obviously real world results are what really matters, but I am curious what the standard is. By the way, we are installing Lunos HRVs for IAQ with spot ventilation for the baths, kitchen and laundry.

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  1. davidmeiland | | #1

    I don't know if there is a specific protocol for PassivHaus (or Passive House) testing, but in general I would not expect to tape off bath fans for a blower door test. Those should be tested with their exterior wall terminations in place, and if you use good ones, added leakage should be negligible. I agree that the built in dampers are not all that tight, and will have noticeable leakage. I would not tape off a range hood either.

    HRV systems may be treated differently. I have tested a few houses with ducted HRV systems and was instructed by the program manager (on a project with partial public funding and specific standards to follow) to tape them off, as there was no damper on the intake side.

    I have had people want to tape off all sorts of things during tests, especially masonry fireplaces. The general idea, as far as I'm concerned, is that you are testing your building methods, and if those methods include big leaks, taping them is cheating. Test the house as it will be during normal use, with the possible exception of intentional openings like HRVs.

    I haven't looked in a while, but I believe there are at least some guidelines in the IECC and the BPI standards.

  2. GBA Editor
    Martin Holladay | | #2

    In my GBA article, "Blower Door Basics," I wrote:

    "Ventilation system intake or exhaust vents (and passive air inlets) are usually (but not always) sealed, depending on the aims of the blower-door test. If the test is being performed to comply with section N1102.4.2 of the 2009 International Residential Code, the section requires that 'Exterior openings for continuous ventilation systems and heat recovery ventilators shall be closed and sealed.' Moreover, in many cases a builder will seal passive air intake vents during a blower-door test to determine the theoretical leakiness of the building’s envelope without any passive inlets."

    As far as I know, the IRC makes no reference to bathroom exhaust vents or range hood vents -- so this may be a matter of interpretation. (In other words, do you consider your bath exhaust fan to be part of a continuous ventilation system?)

    Here is a link to the article for more information: "Blower Door Basics."

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