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Community and Q&A

How to insulate a metal roof that does not have any roof decking?

user-5690923 | Posted in GBA Pro Help on

We are building a red iron framed barn house. The house has all roof framing made out of red iron. A metal roof is being installed on the red iron frame work of the roof. The roof does not have any wood in it. All metal trusses. We are installing a metal standing seam roof on the roof and it will not have any roof decking. My question is: how to spray foam insulation on roof with out spraying directly to metal roof pannels? So when I have to remove the pannels in the future due to an unforseen reason I will not have to redo my insulation. Second question: what type of insulation would you suggest? Open or closed foam? Or do you suggest something different? Thank you for your expertise.

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  1. Expert Member

    I'm a bit confused. Is "red Iron" a brand name for a company? Perhaps it's a regional term? I've never heard of it.

  2. user-5690923 | | #2

    Red iron is just the term the company calls it but all beams are steel.all roof frame work is steel.

  3. GBA Editor
    Martin Holladay | | #3

    Are you trying to avoid the use of wood -- for example, because of your personal beliefs about fire safety, or because of some unusual allergy?

    If you aren't trying to avoid the use of wood, I strongly suggest that you install plywood or OSB roof sheathing on your roof. The sheathing will make it much easier to insulate your house.

    Otherwise, you can let your contractor finish building the shell, and you can then build a "house within a house" to hold your insulation. This latter approach is expensive.

  4. Expert Member

    Thanks for the clarification. The problem with steel framing is that it conducts heats very well. If you want to avoid this thermal bridging you need to place your insulation either inside or outside of your roof framing, not within it. Both ways are possible, and commonly done in commercial construction where steel is more prevalent, but you need someone with the experience to work out the details, like your architect or GC.

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