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A question about Blower Door Testing.

bbirck | Posted in Green Building Techniques on

I am building a new house and am at the stage just before installation of drywall.
I know this is best time for the blower door test, but how can that be performed before the ceiling drywall is up and all the roof ing penetrations,etc are taken out of the process? Doesn’t that huge amount of air leakage pose a problem?

Bill

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Replies

  1. SLS.Construction | | #1

    The drywall isn't meant for sealing the penetrations - Those should already be sealed via flashings, caulking, foam, etc...

    Now if you are talking about venting, you could theoretically figure out the opening sizes & subtract that from the overall - another option is to pressurize the building & check around the windows, doors, crawl space area, etc for leakage

  2. bbirck | | #2

    I guess what I am asking is if it possible to get enough depressurization in the house to check for leaks, when so much air will be coming in thru the soffit vents, etc.

  3. WEG | | #3

    Bill, You asked a great question. I own a blower door and decided to stop by a construction site where a large addition was going up. Everyone was out to lunch so i walked around and it hit me. Unless there is some type a continuous air barrier around all six sides of the cube before the insulation is installed, I can't see how you could use a blower door.

    Are you planning on installing attic insulation before or after ceiling sheet rock is installed? If the answer is after, you could sheet rock ceiling, run the blower door test, then blow in some cellulose in attic.

    Where are you located? http://www.enersavehomeimprovement.com

  4. Riversong | | #4

    Bill,

    What you're testing with the blower door is the integrity of the air barrier enclosure, composed of various air barrier assemblies, made from air barrier materials and components.

    So, if your exterior wall and roof sheathing is your air barrier, then you can pressure test when the outside skin is complete and sealed (that air-sealing might include spray foam, for example, or simply taped sheathing joints).

    If your air barrier is the interior drywall (the Air-Tight Drywall Approach, e.g.), then the blower door test must be performed after all the drywall is installed and taped.

  5. davidmeiland | | #5

    I've seen this approached a couple of ways, and have at least one new-construction test coming up, for which I'm waiting on the owner to decide his strategy.

    Assuming an attic with vented eaves and ridge, probably the most useful time for testing is after the drywall ceiling is installed, but before anything is insulated. This means the drywaller has to come in, hang and tape the lid, and then pull off. This approach lets you test your floor and wall sheathing, your penetrations into the attic, etc., and make improvements as you see fit, recognizing that you'll probably get a bit more tightness from the insulation and drywall. It's a way of knowing if you're within range of your final desired result or not.

    Another, less appealing (to me) method is to try to seal off the soffit and ridge vents temporarily. I've seen one situation where this was done with masking tape and nicely made plugs of old mattress foam. You could test without any drywall doing it this way, although you would be adding the volume of the attic to the equation.

  6. user-757117 | | #6

    Sorry if these are silly questions...
    I will have my own blower door test to accomplish at some point...
    I understand that it is beneficial to do such a test at a stage of construction where weaknesses in the air barrier can be repaired prior to completion...
    Isn't the purpose of a blower door test to verify the integrity of the enclosure's air barrier system?
    Why would one bother with a blower door test if the air barrier is so difficult to define that you must plug the attic vents?

  7. HDendy | | #7

    You have to know what/where your air barrier is to know when it's appropriate to test. If the builder isn't sure where that barrier is, the results probably won't be good. If you have attic vents to be plugged, then that's not where the air barrier is- it will most likely be at the ceiling drywall (assuming standard const.). If the barrier is at the roof, then you'll want to test after the penetrations are also sealed, since they will be a big part of the equation. If you're "plugging" anything, then something's not right- either those locations are incomplete or they won't be plugged later.

  8. Riversong | | #8

    Isn't the purpose of a blower door test to verify the integrity of the enclosure's air barrier system?

    Except for the most conscientious builders, a blower door test is a Pass/Fail exam performed after the house is completed to determine its HERS rating and whether it meets the minimum Energy Star performance standards.

    Even if you perform a test during construction, a final test still needs to be performed to measure the as-built integrity.

  9. David Meiland | | #9

    If you're "plugging" anything, then something's not right- either those locations are incomplete or they won't be plugged later

    So what do you do when asked to test a house prior to insulation and drywall? We are just starting to see BD testing in this market, and the energy code coming into effect here (and elsewhere?) starting Jan. 1 requires testing to a certain level. The more alert folks I know are not wanting to wait until completion to find out if they pass or not, so there is some interest in testing during construction. I think that will pass as the word spreads about how to get the details right, but for now there are going to be folks who want the shell tested, and some of them won't want to get the lid hung/taped first. I'd rather go out there and find a way to help them see where they stand.

  10. HDendy | | #10

    If the sheathing/tape is the air barrier, then that would be the appropriate time to test. If you have a vented attic, then what's the point in including that in a pressure test? The first part of your post a few lines above is exactly what I'm suggesting- complete the air barrier and then test. My opinion is that if we want to build tight and efficient houses then the process needs to reflect that, even if it means the drywall crew has to make an extra trip and the other trades have to wait until air-sealing is completed.
    What would I do? I would first discuss these concepts with the builder and if they still wanted me to test at that time for quality control and/or scheduling, I would do the best job I can and (hopefully) run more tests as the other parts of the assembly are completed.

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