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Attic energy retrofit in Climate Zone 7

cdealcuaz | Posted in General Questions on

Hi all,

Thank you for this amazing resource. I so appreciate the lengths you all go to make us greener builders!

I bought a 50’s ranch house in Anchorage, Alaska and I’m excited to rolls my sleeves up and make it more efficient 🙂

First step this summer is the attic. After I upgrade some electrical, meticulously air seal the many gaps, and detail the vented eaves w soffits to keep air flowing when it’s all said a done — a contractor friend recommends that we hire a spray foam contractor to flash the entire ceiling above the drywall with closed-cell foam to act as a vapor barrier (before we blow in loose fill-insulation). It seem like you all are discouraging low perm barriers in warmer climates, but I imagine since it’s so cold up here this might be a good idea? Can you point me to articulates that talk about retrofitting roof VRB’s in cold climates? (Or energy retrofits in general in cold climates?)

Thanks again!

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Chantal.

    Sounds like you are doing a lot of good work to make you home more efficient and comfortable. I do not think you need a flash coat of closed-cell spray foam for vapor control in this location if you have already done diligent air sealing. That said, it won't hurt and will give you a boost in R-value. But if you go this route, you can rely on the spray foam to air seal the ceiling as well. just make sure to get to any thermal bypasses that will not be cover with the flash coat, around a chimney, for example. I think you'll find this article helpful: How to Insulate an attic floor.

  2. cdealcuaz | | #2

    Thanks so much, Brian. Sounds like if I'm willing to do the meticulous air sealing work, then I can save some money on the foam contractor! (But good to know you dont think it would hurt.)

    I forgot to mention we're also replacing our roof this summer. I assume this climate is too cold to consider insulating above the roof deck w rigid foam to bring the attic into the building envelope?

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