Rice hull concrete for cool room insulation — 20 Comments

  1. I haven’t seen anything saying if you can build a dome using RH tubes. I’ve seen a lot of things saying that RH is not good for load bearing and they either suggest rebar, saplings, or post and beam with a connector beam on top. I’m planning a 20′ diameter main portion with a domed roof. Which way would you recommend?

    • I would not rely on rice hull fill alone when constructing a dome. It might be that using rice hull concrete would be structurally sound, but this would take some testing to be sure. When I designed an insulated domed roof for one project, I specified a geodesic supporting structure beneath the bags.

      • Thank you for the quick response. What do you recommend as a material for the geodesic structure? Also, if I were to have a 2′ deep gravel trench and drove rebar 2′ deeper into that. Could I have 4′ exposed on both sides of the RH bags to stablize then lash 4′ or more to those to get an 8’+ wall instead of post and beam?

        • The geodesic struts can be made from either wood or metal or even bamboo. What you suggest sounds feasible to me.

          • Great. What percentage of the rh/cement mix? Also, which type of cement, Portland?

          • It might take some testing to find the best ratio of Portland cement to RH, but I would suggest starting with about 1:8 by volume. You could also try using hydrated lime for this, which would be more ecologically benign.

          • Not that I know of. BTW, the blog post suggests a ratio of rice hulls to cement is between 3:1 to 4:1

  2. We are wondering about the weight of a cubic foot of rice hull + lime concrete. Would it weight more or less than rice hulls alone?

  3. Keep the idea of rice hull concrete fresh in your mind. Very soon I will publish my latest ideas on low cost housing made with this material.

      • India, like other big countries, loves Portland cement because it’s a big profitable industry that gives kickbacks (payoffs) to investors/insiders/politicians, etc. One reason that Portland cement is affordable is because the industry is subsidized with tax payer money. This boosts profits for the industry and makes it harder for competing products. So it may be difficult to find other types of cement.

      • Any type of geopolymer such as magnesium cement will work. The challenge is finding affordable products nearby.

      • Hempcrete is basically made with a thick slurry of hemp hurds, water, and Type S hydrated lime. I paid $9 yesterday for a 50 pound bag of Type S hydrated lime off the shelf at a big box store. I’m now trying to source ‘construction grade’ hurds…more of a problem. Until I can get them it is worthwhile to practice with rice hulls. Here’s a youtube vid of a high end project using hempcrete:

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