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Community and Q&A

Is the Airtight Drywall Approach obsolete?

Ryan Griffin | Posted in Green Building Techniques on

After months of reading blogs here, I was just about sold on using the airtight drywall approach for all areas of my home that were to be re-drywalled. The main area being the entire attic ceiling which will then have cellulose blown in above it and vapor barrier paint applied over it. After asking my builder and insulator to use the Air tight drywall approach (and offering to pay a significant premium to do so), the insulator sent me this article: http://foursevenfive.com/4-reasons-why-airtight-drywall-is-obsolete/

He tends to agree and thinks that it will not hold up. I feel like some very solid points were made by 475, so I would like to throw it out here to get your opinions. I hate the thought of changing my design this far in, but I need to get this right. So what do you all think about ADA, and are these valid concerns?

Thanks!
Ryan
Minneapolis

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Ryan,
    In my opinion, the Airtight Drywall Approach is not obsolete -- especially for ceilings under unconditioned attics (the application that you are considering).

    Here are a few points:

    1. The advice you saw on the 475 web site was posted by a company that sells air barrier membranes from Europe, so it is clearly in the company's interest to convince readers that the products they sell are essential. Consider the source of the advice when you evaluate it.

    2. You don't need to install an expensive membrane to create an air barrier at a ceiling under a vented unconditioned attic. The logical location for the air barrier is at the drywall level; above the drywall goes thick cellulose. You are done.

    3. Making sure that your electrical boxes are airtight -- the most important feature of the Airtight Drywall Approach -- makes eminent sense in this location.

  2. User avatar
    Aaron Birkland | | #2

    Totally agree with Martin, ADA is not obsolete, particularly in retrofits.

    Was your builder or insulator familiar with ADA before you asked them? Do they have any experience with it? If not, that could explain their skepticism. Unfortunately, that could also explain their "significant" price premium - as it it would represent a risk to them if they are unfamiliar with the actual impact on labour & materials, as well as expected performance and customer satisfaction.

  3. Ryan Griffin | | #3

    Thank you both and I appreciate the tip on the electrical boxes. We will go ahead with the plan. You're correct that neither builder nor insulator (nor I) have used this approach. I know I am paying for their learning curve, but I kind of justify that and other energy related upcharges with the hope that they may use this again elsewhere in the future.

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Ryan,
    If you are interested in more information on the Airtight Drywall Approach, here is a link to an article on the topic: Airtight Drywall.

  5. Floris Keverling Buisman | | #5

    Ryan and Martin,
    would like to add the following. Yes, we at http://www.foursevenfive.com do indeed sell airbarrier materials (ProClima's INTELLO smart vapor retarder) that have been used in many Passive Houses and other high performance buildings that have been blowerdoor tested (and retested after a few years) to confirm to 0.6ACH50 limit.

    The points we bring up in out blogpost are true:
    1-ADA connections are not flexible (buildings move...),
    2-ADA is discontinuous (does not run from floor to floor or room to room)
    3-Drywall is a sacrificial layer (see image, but more prevalent are screw holes, etc)
    4-ADA does not address/reduce the number of penetrations made in the airbarrier by outlets etc
    5-ADA is not a smart vapor retarder

    Furthermore the IECC does list at interior gypsum as an airbarrier material in C402.4.1.2.1 but notes:
    "Materials in Items 1 through 15 shall be deemed to comply with this section provided joints are sealed and materials are installed as air barriers in accordance with the manufacturer’s instructions."

    GP and National Gypsum do not provide any instructions how to install interior gypsum as airbarrier or airtight (and for exterior recommend a WRB for airsealing), and although USG does mention acoustical sealant and air-tight connections - it does not provide actual instructions nor address points 1,2,3,4 and 5.

  6. User avatar GBA Editor
    Martin Holladay | | #6

    Floris,
    I stand by my advice.

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