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Concrete block insulation

pCFQgiM5da | Posted in Green Products and Materials on

Hi Martin. First, thank you & fellow GBA posters for providing valuable insight on a variety of topics.

My question pertains to insulating 8″ concrete block that will be used on a commercial single story building along with utility brick in the northern midwest.. The piers will use 6″ block with brick. I have primarily done residential work & do not have a lot of commercial experience.

From what I have read, there are a few choices on insulating the block:

1) the hollow cores can be filled with foam beads
2) the hollow cores can be filled by pumping foam (I’m assuming closed cell?) but restricts drainage
3) install polystyrene inserts like Korfil (helps keep cores open for drainage) & can be grouted
4) forget all of the above b/c the face of the block will exhibit more thermal conductivity negating any benefits of insulating the block’s core so use rigid foam to insulate between block & brick
5) insulate the core & face of the block
6) go with a preinsulated 8″ block such as Omni block (then what do I use on areas with 6″ block?)

The preliminary takeoff (mine) calls for 6,000 8″ block, 1,000 6″ block. Thank you, looking fwd to your thoughts & reasoning.


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  1. GBA Editor
    Martin Holladay | | #1

    You got it right with number 4: "Forget all of the above because the face of the block will exhibit more thermal conductivity negating any benefits of insulating the blocks' cores, so use rigid foam to insulate between block & brick."

    The answer is, use a continuous layer of rigid foam insulation. It can either be installed on the interior of the concrete block wall or the exterior; exterior insulation is preferred.

    To avoid the usual pitfalls, remember:

    1. Maintain continuity between the thermal barrier installed on your wall and the ceiling insulation.

    2. Be sure the foam is thick enough to meet minimum code R-value requirements.

  2. Riversong | | #2


    Other options that you may not have considered are using ICFs (insulated concrete forms), of which there are at least a dozen proprietary versions (some a bit more green than others), or the ThermoMass poured concrete wall system that places the XPS (up to 4") in the midline of the concrete wall for both a thermal barrier and a capillary break.

  3. user-869687 | | #3

    There is also an alternative to plastic foam, which is mineral wool insulation. There are products intended for exactly this application (masonry cavity walls) made by Thermafiber and Roxul. R-value is similar to EPS foam, cost is competitive and there are a few advantages. The manufacturers' websites explain the benefits. (I seem to be isolated in liking this material, because nobody else mentions it.) Mineral wool is more popular in Europe, where people are less inclined to wrap buildings in Styrofoam.

  4. ICF BOB | | #4

    Look at InSoFast panels. R10, two inches thick, plasticm attachment strips built in 16 inches oc.Easy install.

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