some thoughts from Dozer
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double wall construction using foam insulation

image dsc20438.jpgI noticed a building site around here which was engaged in double wall construction. I really like what I saw on this site. Previously I noted this technique used on some luxury houses, previous article on double wall. There are many reasons why I like the idea. First off, it adds to the strength of the wall structure. Secondly, the incremental cost increase is not that great. And, primarily as to its insulating ability.

image dsc20442.jpgThis installation used common Styrofoam sheets as the insulation type. The foam is sandwiched in between an exterior wall of the small red brick and an interior wall of common cement blocks. Certainly having the insulation solves the problem of having pests in the opening, and it is a porous good insulation source. Other types of more expensive insulation could be used in its place also.

image dsc20439.jpgI also like the idea of a raised foundation that they were using, but don’t think it is applicable on every project acces. Primary advantage: allows access to plumbing, reduces risk of flooding and makes pest entry (eg. termite) more difficult.


  1. Have read that some double-wall construction folks have used burnt rice husks as insulation between the blocks. Was wondering if the insulation R-Value for foam is significantly greater than the rice husk method.

    Any ideas, fellas?


    Boon Mee

  2. I would image that the burned rice husk material and the foam have a similar R value, but only a guess. The burned rice husk is a organic fine powder material which you would pour into the wall cavity, where as the foam is set in. Hope to have a picture of the rice husk material posted soon.

  3. I have used cavity construction for exterior walls on both of my Thai builds. Did not use insulation as the air gap alone provides a good solar gain barrier. I laid the blocks on my first house with 2 Thai guys mixing, watching Thais lay blocks is painful when you have spent most of your life constructing in the UK. Also used 2M spaced wall ties, even though walls are not load bearing it helps with expansion stability. Using the double wall method also allows you to set windows with decent internal and external reveals, a much more pleasing look. I hate the traditional flush fit windows that the standard Thai single block wall produces. Reminds me of caravans and portable cabins.

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