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name ONE GOOD REASON to air seal cathedral ceiling insulation baffles OTHER than air washing insulation (Rockwool insulation)?

BuildingFun | Posted in General Questions on

After scouring the internet and GBA forums for every cathedral ceiling and insulation baffle article ever written, I STILL can’t find a good reason to air seal the insulation baffles on a cathedral ceiling.   At first, “wind washing” seemed to be the answer but after reading a couple articles (one from here) on wind-washing of rockwool, it appears to be an irrelevant concern.   
Sometimes I wonder if we get so caught up in trying to save every fraction of R value that we forget the cost and labor that goes into doing so?   I also have trouble believing that anyone has ever air sealed these baffles, outside of members of this forum, yet thousands of cathedral ceilings have survived without doing so (although admittedly, many fail for other reason).  

I also understand that it has been written that “air impermeable baffles have been used widely without moisture issues because of drying through sorbtion and diffusion”.   I agree, much drying must occur through sorbtion but maybe we’re also missing the point that drying is occurring outward through these leaky baffles as well?   

With that being said, can anyone else come up with a good reason for spending labor and materials on air sealing these insulation baffles of a cathedral ceiling, other than “because ____ said so”?

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  1. Expert Member
    Michael Maines | | #1

    In certain conditions, stormwater may be able to enter the vent channel--I've seen it happen often on coastal projects. I used to specify the insulation baffles to be shingle-lapped for drainage as a result. Now I try to design more clever soffit vents and spec an Airvent Shinglevent ridge cap that keeps most water out, or I spec a Sarking membrane system that obviates the need for conventional vents.

  2. Expert Member


    I can't. The minor gains in providing a secondary air-barrier don't offset the extra labour involved in sealing the baffles.

    That said, I don't think you should ever encourage air-leakage through an assembly as a strategy to increase drying, so I'm not sure leaky baffles are a benefit in that regard.

  3. BuildingFun | | #3

    Michael Maines- Thanks, I guess that makes sense in that situation. For all other situations, I still cant find a reason why it should be done.

  4. 5Stud | | #4

    I am waiting for the name one good reason for a cathedral ceiling thread!

  5. Expert Member
    BILL WICHERS | | #5

    I think Michael gave a pretty good reason -- if you are in an area prone to heavy wind-blown rain, then sealing those baffles helps to make a sort of roof rain screen, and offer some extra protection. In other areas with less harsh weather, the primary thing any "sealing" does is just to hold the baffles physically in place, so it's not a big deal to do a fancy air sealing job here.


  6. Deleted | | #6


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