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Material for preventing thermal bridging at steel beams and columns?

Pat Kiernan | Posted in Energy Efficiency and Durability on

I have seen drawings showing an insert at the base of steel columns and where a steel beam bears on the top an exterior concrete stem wall (or in a beam pocket) that is intended to reduce thermal bridging at those points.

Does anyone know where to get this sort of material? A local structural engineer mentioned a carbon-fiber product that is quite expensive. He didn’t think it would be worth the bother and expense. Anchor bolts (2 to 4) at each point will bypass the thermal break material.

I’m in climate zone 6B. The house I’m designing has two column pads interior to the basement. The floor is about 7 feet below grade. Basement floor insulation is R16 to R20.

A wide flange I beam bears on the top of the concrete wall and will allow at least 6 inches of insulation (2 in the wall 4 exterior) beyond the end of the beam. I haven’t decided yet if I will use a formed concrete wall or ICF — depends on local costs.

I’m using steel to allow for wider spans and increased headroom.

I welcome any advice or comments.

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    The loading & material has to be specified by an engineer. You may be able to use autoclaved aerated concrete (assuming you can find it), which isn't ridiculously expensive (they build whole walls out of it), and has a reasonable amount of R at 6" or thicker, and load bearing capacity. It comes in several densities- load capacity goes up (and R-value down) with increasing density.

    You can probably surf the necessary details (or have the engineer/architect do it) on the Aercon website:

    http://www.aerconaac.com/product-sizes.html#Standard Block

    This is a fairl common building material in Europe, but a special-order in the US, with few manufacturers & distributors in the US.

  2. Expert Member
    Michael Maines | | #2

    It might be cutting it close on load capacity, but at 500 psi, this product would support typical residential loads: https://foursevenfive.com/product/compacfoam-200/. You may need to have an oversize plate welded to the bottom of your column.

    Another idea would be to have the column's bottom plate and anchor bolts sized so they support the entire load. This is common in commercial work, with nuts both above and below the plate, then the gap is filled with non-shrinking grout. You could see if your engineer would allow non-structural spray foam instead of the grout.

  3. Jon R | | #3

    Maybe you can make the steel beam stop short of the wall and bear on another post next to the wall. That moves the issue to a less exposed area.

  4. Jonathan Lawrence CZ 4A New Jersey | | #4

    Pat,

    I can offer 2 options for you as follows:

    1) General Plastics makes a column bearing block called LAST-A-FOAM R 9300 (https://www.generalplastics.com/wp-content/uploads/2016/11/Construction.pdf) It comes in multiple compressive strengths all the way up to 1800 psi. You get roughly R-2 per inch. I have a 70,000 point load under a steel column that I need to deal with and my structural engineer has approved the 1000 psi version for this. Dow makes a similar product (http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_06ea/0901b803806ea99b.pdf?filepath=styrofoam/pdfs/noreg/179-04330.pdf&fromPage=GetDoc). However, I put a call into them 3 months ago to inquire about purchasing this and I am still waiting for a call back.

    2) As Michael mentioned above Compacfoam has a product that can perform the same function and you can get compressive strengths as high as 1400 psi, albeit with a 12-week lead time. If your loads requirements are less than 500 psi, then you can get the product in short order as 475 stocks that version. This product has a higher r-vaue than the General Plastic's product but lead time was an issue for me.

  5. Tim R | | #5

    They are using fiberglass plate and angles to provide thermally broken structural connections on high rise wall systems. The FRP material is commonly available. http://www.strongwell.com/products/structural-shapes-and-plate/ Looking at the specs the W (m dot K) = 0.58 the inverse is -so R1.7 - I think that's correct? This can be a bearing plate between the steel and concrete. They also offer fiberglass bolts and nuts.

  6. Jon R | | #6

    I'd say the US R value is .25.

  7. Brendan Albano | | #7

    Here are a few more products you could check out:

    Armadillo Structural Thermal Break: http://www.armadillonvinc.com/index.php/products

    Fabreeka Structural Thermal Break: http://www.fabreeka.com/Products#/filters=Thermal_Break/detail=Structural_Thermal_Break_Pad_Connection

  8. Pat Kiernan | | #8

    Thank you all for your helpful suggestions!

    I'll do some research on the products mentioned above and see what my structural engineer thinks.

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