Straw-Clay Insulation

Stray-clay, sometimes know as Light Clay is a natural insulation far superior to conventional types because it is non toxic, reasonably self supportive, and resistent to rot, vermin, or fires. It also has a low impact on the environment because it made from an agricultural waste product and clay. This combination of thermal mass (the clay soil) and thermal insulation (the fiber) works together to create very comfortable interior climate and a high level of energy efficiency. The clay is mixed with water to form a consistency which can vary from a thin “cream ”slip to a thicker “ peanut butter ” slip. We mixed a medium consistency with an electick paddle mixer. Next, on a plywood mixing base, take a few handfuls of straw and poured over some slip. Toss it around until you cannot see any gold color, just an even coat of slip.


Eva tossing the straw and slip

To prepare and existing structure for straw-clay insulation remove the inside dry wall to expose the studs. Then screw a piece of plywood on the bottom to create the base. Fill with the slip-coated straw and tamp down. Once the straw-clay is filled to the top of the plywood, move it up and secure so the next course can be installed. Ther is no need to wait for the straw to dry before adding more insulation. The same process is completed for brand new construction except the benefit of starting from scratch is that you do not have the exterior wall to limit your access and ease of tamping. However, the roof must be built before the insulation is installed. Stray-clay has an estimated R-value of R-19 for a dry 12“ wall. Before any finishing/plaster allow full drying. This can take anywhere between month to several months depending on the climate and season of the building.

outer board removed and ready to move up the wall

outer board removed and ready to move up the wall

working on the top of the wall

working on the top of the wall




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