Hempcrete

Are you guys hip to this? In all honesty I’ve just begun to take a look at it. Hempcrete? The hurds are mixed with lime and water. The mixture is poured or sprayed into or onto a mold. When it dries it becomes hard. The insulation properties are outstanding. It’s bug and mold resistant. Enter “hempcrete” into your favorite search engine. There’s a slug of videos out there.

From what I’ve seen the hemprete is put between the studs of a regular lumber framed house. The hemp then becomes the wall. In one video they have a length of plywood spanning the studs, inner and outer, and fill the resulting mold. After it dries up they go to the next row. In another, from Co Cork, Ireland, full sheets of plywood have been affixed to the interior of the studs and the guy is spraying the hempcrete filling the void from the interior outward. In one photo I saw it appeared the hempcrete was precast blocks.

Obviously the mixtures vary with the intended use. One cat was using a roto-tiller for the final blend of water, hemp and lime. It was to be used as insulation so a very dry mix was indicated. I’d take a wild guess and say a person would want it a bit wetter for spray; between the two for a molded wall?

I’ve had a project rolling around in my head for quite some time now. The exterior siding on this shack is asbestos shingles. I’ve been looking at doing some sort of plaster right over the top of it. Being in the PNW that can be a bit tricky due to all of the moisture. I’ve been formulating a plan called an open system. You use two moisture barriers… Never mind. You don’t want’a know all’a that.

In one video the guy is dumping a sack of stucco lime into the mixer. The hurds are in what looks like a 25 pound bag. The bag is labeled from some sort of feed co-op. I figured I’d just take a quick look at hurd pricing. Now, granted, this pricing is from the first place I looked- I certainly hope it’s not a real indication of the cost.

$10.00 a 5 pound bag (120 bag price. FOB China).

I’m thinking I should be checking out the feed co-ops, eh?

Seriously, when you’ve got a few minutes to burn go tube’n and check out the hempcrete thing. Down in North Carolina a very cool house has been built with it. In England a warehouse. You wouldn’t mind chasing a little pricing for me while you’re out there, would ya’?

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