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How do I insulate around HD3B holddowns?

TaosDoug | Posted in General Questions on

I am building a tiny house with 4″ walls. I have a large number of Simpson HD3Bs, and am a bit concerned that the space contained between the sidewalls of the hold down are going to be filled with great stuff, but nothing more. What is conventionally done about insulating around awkward shaped steel in the wall cavities?


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  1. GBA Editor
    Martin Holladay | | #1

    You're right that the thermal performance of your wall will be somewhat degraded by these Simpson hold-downs. Steel is conductive, and these hold-downs also take up room that would be best filled by insulation.

    Fortunately for you, you are building a tiny house. A tiny house is generally easy to heat and cool, so insulation details that are imperfect can still work.

    If you were building a Passive House, or a conventional home where you were concerned about thermal bridging in your walls, the solution would be to install a continuous layer of rigid foam or mineral wool on the exterior side of your wall sheathing. For more information on this approach, see these who articles:

    How to Install Rigid Foam Sheathing

    How to Design a Wall


  2. TaosDoug | | #2

    Martin - Thank you. Although it is a tiny house, there will be a continuous layer of 1" XPS. Walls are actually 4", not 3 1/2, and the hold downs are under 3" wide. I guess I've no choice but to go for it.

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