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Community and Q&A

Steel Beam Pocket Insulation Help

skycappy | Posted in Green Building Techniques on

I’ve researched this site and can’t find an answer to my particular situation. 

I’m insulating our basement walls with 3” of Polyiso. The cement walls are poured and have 12” exposed above grade. No water issues. 

I’m stumped as to how to insulate the steel beams sitting in the cement wall pockets. Each pocket is 6 to 8 inches wider than the beams. Exterior above grade insulation is not an option and they sit in their pockets with a gap behind them of maybe a 1/4” at the exterior side.


Should I insulate the pocket with the fiberglass insulation they originally had, or spray foam it, or leave them exposed, or something else?


Secondly, directly below the pockets, each steel beam has a vertical steel plate with bolts securing the beams to the basement wall. I was going to cover it with Polyiso. Is that acceptable?


Any recommendations would be much appreciated. Thank you

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  1. Expert Member
    BILL WICHERS | | #1

    Spray foam has the advantage of being a fully adhered insulating material, which means it's less of a moisture issue, and that means less chance of rusting. My usual solution here is to paint the beam with Rust Oleum's "Rusty Metal Primer", then sometimes a rust inhibiting enamel topcoat (from the same "Stops Rust" product line) if I care about appearance. After putting on the special primer, it's usually pretty safe to insulate with rigid foam.

    You could try insulating the entire beam box-over style, or the first few feet out from the wall will help some too. If you can't insulate on the exterior of the wall, your options are limited here.


  2. skycappy | | #2

    Thanks Bill for responding. I’ll implement what you recommended.

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