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Community and Q&A

Polyiso performance in cold weather

Wannabegreenbuilder | Posted in Energy Efficiency and Durability on

I once heard Martin Holladay say in an offhand remark that polyisocyanerate foam performs less well as temperatures drop.  Why does this occur and how much of a decrease in performance can one expect from 100 degrees F down to -20 F?

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    1. Wannabegreenbuilder | | #3

      Thank you

  1. charlie_sullivan | | #2

    Note that if you have thick insulation, it's only the outer part of it that gets cold. So a good way to use polyiso in climates that get down to -20 is with something else as the outer layer and polyiso elsewhere in the stack.

  2. Expert Member
    BILL WICHERS | | #4

    Note also that not all types of polyiso are especially bad about this. It's not usually something that needs to be worried about, unless perhaps you're in one of the WAY North climate zones with a lot of VERY cold weather. If you're in one of those areas, a layer of EPS on the exterior will help to mitigate the issue. Polyiso's main advantage is that it is the highest R per inch over most of the normal temperature range it will see.

    Note that Dow Thermax advertises that it does NOT suffer from the "reduced R in cold weather" issue.


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