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What is a good way to attach insulation to earthen walls?

AyTGxzTyGS | Posted in Green Building Techniques on

I’m currently looking at building a small home with a focus on using local materials. This is certainly not a new concept in the green building world. Local materials for me (in Golden, B.C, Canada) are wood, earth and stone. There is a Roxul manufacturing plant in southern B.C as well.
My thoughts are to build Compressed Earth Block walls, wood-framed roof and floor systems, and probably a rubble-trench foundation with an earthen floor or concrete slab-on-grade. Many details to work out.

It has been shown here

that exterior walls made of earth are suitable for cold climates if they are insulated,and if the effects of multiple freeze-thaw cycles on the exterior of the walls are dealt with. The study looks at different configurations and insulation locations, and is specifically considering rammed earth walls. I’m more interested in CEB, as there is no need for formwork and the blocks can be pre-manufactured either on or off-site, or a small crew can be pressing blocks while another prepares the foundation.

Exterior insulation makes the most sense to me, as it will protect the earthen wall from the extremes of temperature. The question is, how do you fasten a rigid insulation such as Roxul Comfortboard IS to the exterior of a CEB wall in a way which doesn’t overly complicate the construction? (There is at least one builder I know of who is building with CEB walls wrapped with strawbales for insulation, but I don’t have a local source of strawbales and if I did I use them I would probably leave the CEB’s out altogether.)

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  1. GBA Editor
    Martin Holladay | | #1

    I would experiment with concrete fasteners and masonry fasteners. You have begun to realize that some natural building materials like earth and straw can be hard to integrate with the features of a modern home.

    Good luck.

  2. zdwiel | | #2

    I'm designing and starting to build a similar home. I am using CEB blocks on a rubble trench foundation with wood framed roof and earthen floor. For insulation I am using rice hulls in a 12" cavity between two CEB block walls. I'll be posting plans on my site soon as well as detailed building instructions as I go.

    I notice that this post is from 6 months ago. Have you started building yet?

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