Mana – Natural Materials

We originally thought to have straw bale walls. We had come across a straw bale house in Findhorn in Scotland and were rightly impressed with how well insulated it was. However when we heard of hempcrete and were headed for a trip to East Yorkshire we decided to visit East Yorkshire Hemp and see for ourselves. We were taken to see a house renovation and a new build, both onsite, and were surprised by the feeling of comfort within the house. The air felt like a soft blanket wrapped around us and the acoustics were incredible. It felt like home. We found out that hemp is highly insulating but also breathable and that it regulates humidity. It can be sprayed or cast around a timber frame to provide an airtight, thermal bridge-free structure that needs no added layers, apart from render or cladding on the outside and plaster on the inside. Plus it locks up more carbon than is used to produce it and also continues to absorb carbon during its life as wall. This was a real selling point for our objectives for our build, namely high quality, zero carbon, biodegradable and simple. We intend to cast the hempcrete which is a process we can get involved with, really getting our hands into the build. The only ingredients are hemp shivs (the core of the stem), lime and water which are all mixed on site and placed between shuttering and tamped down. The whole house should only take just over a week.

To finish the walls we realised that we needed to have a breathable finish which will complement the breathability of the hempcrete and we looked at lime or clay plaster for the inside and lime render for the outside. Both materials are breathable and help regulate humidity and so they complement the qualities of the hempcrete. We settled on clay plaster for the inside as it is more natural and comes in some lovely colours. It’s pretty hard finding people who can work with these materials but we’re looking into having the School of Natural Building run a course which means 8 to 12 people, including us, learning and practicing over 5 days. It won’t compete all the with but it will make a valuable contribution. Then we can either finish the rest ourselves, with our new found skills, or contract somebody to finish it for us.

So if anybody reading this wants to try either hempcrete casting on a voluntary basis or clay plastering on a School of Natural Building course then get in touch. We plan to be doing hempcrete casting in summer and plastering around September.