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How do you attach strapping at the corners for 4″ of exterior rigid insulation?

78LLiEohNx | Posted in Green Building Techniques on

Our firm is developing a range of sustainable wall section details for our clients to select from. For several variations, we have 4″ of rigid polyisocyanurate foam outside the structure. Along the walls, screws through 1×4 strapping fix the foam back to the studs. At the corners, however, this becomes difficult. What do you suggest? Any clarification would be helpful.

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  1. user941025 | | #1

    There are details in the Lstiburek Builder's Guide.
    ISBN: 156158374X. Support your local library!

  2. user-869687 | | #2


    Use wide furring strips, say 1x8s, and tack them together at the corner.

    I would also encourage you to think for a minute about this word "sustainable", and to use it literally instead of metaphorically. The literal meaning is "able to be sustained", or the opposite of "unsustainable". It's interesting that the term "unsustainable" is almost always used literally (I would say, used correctly). Think of "sustainable" as the reverse of that, instead of meaning "somehow good for environmental concerns". As for these wall section details, a more appropriate description might be "high R-value wall details".

    I make a point of this because I think accurate use of language helps people to understand what they're talking about. For example, you could have some super high-R wall design that's terrible on environmental grounds (based on materials used or toxicity), and high R-value isn't necessarily the same thing as "sustainable".

  3. 78LLiEohNx | | #3


    Thanks for your answer (also, it's always interesting to hear from great American patriots. Jefferson was a good architect, after all. I agree with you about the use of the word 'sustainable' - and we often don't think carefully enough about it when we use it. I think the difficulty is that sometimes one is thinking about a range of considerations for construction (wall sections in this case): affordability, r-value, thickness of wall, ability to be modified in future, toxicity of materials - and it's easier (or perhaps lazier) to use a coverall term like 'sustainable' or 'green'.

    Being specific is good, so again, thank-you. Keep upholding clear communication - there's not enough of it in the architectural world!

  4. wjrobinson | | #4

    While we are defining sustainable let's use the word toxic a bit less.

    To me if something is toxic, then ten out ten will die from exposure to it.

    Not a fan of the new way overuse of toxic. Everything simply is NOT toxic to the point of instant death IMO....

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