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Are there alternatives to styrofoam as rigid slab insulation?

johndavies2 | Posted in Green Building Techniques on

I am trying to build a home with minimal/no (?) plastics. As a minimum, we are excluding PVC materials, but may need PS, PE products in various places. Slab and foundation wall insulation are one of the areas I am looking at now for alternatives.

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  1. GBA Editor
    Martin Holladay | | #1

    You can build an uninsulated foundation (a basement or crawl space) and make the thermal boundary at the level of the first floor, using cellulose or fiberglass insulation to separate the basement/crawl space from the living space above.

  2. johndavies2 | | #2

    Thanks for that. The basement is full height and has some finished rooms (bedroom, bathroom). We managed to find some 'benign' waterproofing for the foundation walls (bentonite clay), but the insulation package is a bit tricky.

  3. GBA Editor
    Martin Holladay | | #3

    Although there may be many reasons to strive for a plastic-free house, it would be a grave mistake to end up with a poorly insulated house because of a misguided decision to avoid the use of XPS.

    To be green, it is essential that a house be extremely well insulated and use a minimum amount of energy. If a house has been designed with below-grade finished rooms, it's a little late in the game to ask the question, "How are we going to insulate a below-grade slab without using EPS or XPS"?

    If a plastic-free house is a top priority, put all finished rooms well above grade. If someone wants occupied rooms below grade, they'll need to be insulated with foam — because poorly insulated rooms aren't green.

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