I’ve had the pleasure of corresponding with Paul in Chiang Dao, a district north of Chiang Mai, Thailand. We’ve been discussing how to build an earthbag house with bags filled with rice hulls. Rice hulls are super cheap, fire resistant, superinsulating, and super lightweight and easy to work with. Rice hulls are the by-product of processing rice (the protective coating around the grain), so they’re 100% natural and sustainable.
I’m very happy to see others experimenting with alternative building techniques such as rice hulls. I can’t overemphasize enough how just one successful project could lead to many thousands of other structures. This could easily happen due to the extremely low cost and simplicity of construction. In our area, a half semi truckload of rice hulls cost about $25. Recycled bags for half price are widely available from farmers and feed stores.
A few details:
– lower courses of bags are filled with gravel, which sit on a rubble trench
– bags of rice hulls are less stable than tamped earth and so extra reinforcing is required (ex: rebar on each side of the wall tied tightly together). This could be added after every 4-5 courses so walls can’t shift.
– tie courses of bags together with twine for added stability (this also makes it easy to attach fishing net or plaster mesh if needed)
– protecting rice hulls from moisture damage is key, so plan accordingly. The privacy wall would benefit from a protective covering such as a cap of roofing tile.
The house is still a work in progress, but as you can see they’re making good progress. Notice how they’ve improvised here and there to add extra reinforcement. My main concern now is seeing the roof get built before the upcoming rainy season hits. Rice hulls can rot if they get wet, and they probably will get wet if there’s no roof or other protective covering.
Here’s some background information on rice hulls.
Paul’s rice hull wall photos on Flickr. (Hope he adds more in the future.)