Daub

Insulation is the most expensive part of making your own house, or anyone’s house, as a matter of fact. It’s what keeps it warm, and what makes your heating or air conditioning costs: great insulation keeps you warm during winter and cool during summer, ideally with as little external intervention as possible.

My question becomes: how can I insulate a house as best as possible, without ruining my savings? And that’s how I learned about daub.

I come from a region of France where wattle and daub, like in many parts of the world, used to be the traditional way of erecting houses. The Industrial Revolution and the generalization of concrete gradually changed how we build things, but the olds ways are making a comeback to provide low-impact sustainable building techniques.

You only need three things to make baud: dirt, straw, and a bit of water. It’s the simplest and cheapest insulation technology you can have: about 0.17 λ (thermal conductivity, the lower the better), against 0.95 λ for concrete blocks. It conducts three times more heat than glass wool but you just have to make thicker walls to achieve similar results. 

Unlike glass wool though, daub can be used as-is to insulate a house. You make a wooden mainframe (wattle), fill the voids with daub (you mix the dirt, the straw, and the water to obtain a natural cement, neither too liquid nor too thick), and voilà.

The problem is daub doesn’t like repeated exposure to water, so you need to cover it with lime plaster and make a buffering zone between the ground and the daub. It also takes more time to apply, because you have to compress the dirt and straw mixture with your body weight to increase the density. Some people don’t like the rough look of it, but I find it charming, and you can always add cladding to cover it. 

More importantly, daub can last centuries, doesn’t create any waste, and does not involve a polluting industrial process. When you see the cost of housing and its impact on the environment, even a dirt house becomes an empowering thing.