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Community and Q&A

Durability of Unvented Roof with Fiberglass Batts

cody_fischer | Posted in Energy Efficiency and Durability on

I just bought a 100+ year old home in climate zone 6A. The seller recently finished the attic space and provided me the attached drawing of how they insulated the attic ceiling. All insulation is fiberglass batts.

Despite the quality of their other renovations, I am certain they didn’t pay particular attention to air sealing or vapor management.

How high risk is this set up for mold, rot and failure?

I expect we will need to replace the roof in 3-5 years, at which time we can add continuous exterior insulation or address any issues from the top side.

As long as there is no bulk water intrusion, is that time horizon safe enough to not bother touching this?

Do I need to rip it open and address it ASAP?

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  1. rondeaunotrondo | | #1

    It’s likely fine. Building Sci Corp had looked at your exact roof set up although with ridge vents and from my understanding deemed safe. Also search for the recent article by Rachel White of Byggmeister on GBA detailing these in current retrofits.

    1. Expert Member
      Akos | | #2

      Key here to Will's comment is there needs to be venting in the mini attic up top. If you have a ridge vent or gable vents, it seems to hold up well enough.

      If you do have some uglies like shot gunned ceiling with canned lights or bath fan venting into the attic, you want to address those as no amount of venting can save you from big air leaks.

  2. cody_fischer | | #3

    Thank you both for the peace of mind on this. Glad I can wait until we need a new roof to address it the right way.

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