That Time I Worked on a Hempcrete House…
I try to keep an open mind towards all methods of natural and green building. There are still many techniques that I’d like to get hands-on with such as adobe, straw bale, and hyperadobe. Before we built our first earthbag house in 2009, I did a lot of research into the different options available. A friend who lived in Alaska had come across a book called “The Straw Bale Yurt Bible,” and I was close to going that direction until I heard about some straw bale homes that had become mold factories in our wet climate.
Several years ago, I got an opportunity to work on a hempcrete house for a couple of days. By that time I’d heard quite a bit about the technique and was very excited to get a chance to try it out. One problem I quickly noticed was the amount of preparation required to do it properly. Large frames had been erected and had to be moved regularly, keeping one skilled carpenter and his assistant incredibly busy. I’m a “set it and forget it” kind of guy, but doing hempcrete with wall forms takes a lot of planning and preparation.
The next major problem I came across was burning nipples. Yes, you read that right. Hempcrete is basically hemp fibers suspended in hydrated lime. Lime is very alkaline and can burn and dry out sensitive skin. The lime had soaked through my sweat-saturated shirt and made it’s way to my manmaries. Ouch!
A different approach that would bypass both of the aforementioned problems is to make hempcrete bricks. I haven’t had the opportunity to try this out, nor have I heard direct reports about it, but it would solve some of the issues I experienced.
Advantages and Disadvantages of Hempcrete Building
Much can be said in favor of hempcrete building.
- It sequesters carbon, potentially decreasing the effects of climate change. It also continues to absorb carbon after it has been built. Hemp is a fast-growing wonder-weed and can reach maturity in 90 days!
- The walls are extremely insulative.
- Non-toxic. Since no pesticides or fertilizers are required to grow hemp, it is an extremely safe material for those working with it or living in it.
- Long lasting.
- Mold and pest resistant (including termites).
- Naturally regulates moisture levels.
- The walls also have significant thermal mass, leading to better indoor temperature regulation.
- I’m not sure if it’s the case anymore, since farmers are able to domestically grow hemp in some states, but it used to have to be imported which greatly increased the expense of it. I think the hemp we were using was from Canada.
- The forms are costly to build, difficult to work with, and will ultimately likely end up in the landfill.
- Burning nipples(!).
- Not meant for contact with moisture.
- Not meant to be load bearing – can be used as infill in a post and beam structure but not meant to support a roof by itself. This isn’t really a problem, just a limitation.
After researching a bit, it seems that making hempcrete bricks is becoming a more popular method. This solves some of the issues I faced when building. Have you worked with hempcrete? If so, what are your experiences and thoughts?