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Insulating the exterior of my stemwalls

user-2391129 | Posted in General Questions on

Insulating the exterior of my stemwalls: The question is, should it drain between the stemwall and insulation, or outside between?

Stem wall-damp proof-drain-insulation or Stem wall-damp proof-insulation -drain?

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  1. GBA Editor
    Martin Holladay | | #1

    When you say "drain," do you mean "dimple mat"?

    If you're talking about dimple mat, the answer is: either way can work, and different dimple mat manufacturers provide conflicting advice. The topic will be covered in an upcoming "Musings of an Energy Nerd" blog.

    Two details you need to figure out:

    1. The rigid foam insulation needs to extend at least to the top of the foundation wall, whereas the dimple mat is usually terminated at grade.

    2. You need some type of flashing at the top of the dimple mat to prevent soil (or, more likely, soil particles + rain) from entering the air channels.

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