Mana Insulation

Insulation is key for comfort in the modern climate, both in cold winters and ferocious heat waves. The insulation is in the walls, the floors and the roof. Our walls are made of hempcrete and you can read about those in our other blog post.

Before we deal with what the floor and roof insulation consists of we will just explain the structure of those parts. The timber frame is constructed using I joists in the floor and roof. These are beams that are made in the shape of an I using long timbers (flanges) at the top and bottom held together by thin OSB webs in between. They are incredibly strong and also very light. Most insulation products, including natural materials, are made for solid blocks, usually wood fibre, hemp or sheep’s wool,  and are fitted between the joists which are at about 570mm apart and they just press fit into that space. With I joists the distance between joists varies from 500 across the flanges and 591mm between the webs. Choosing insulation for I joists means figuring out how to fill the floor or roof void without having to cut every piece. A bit like a 3D jigsaw puzzle. This is the case for both floor and roof joists.

For the floors we chose sheep’s wool because it is quite flexible but does squish down a lot, in order to fill all the crevices, but it’s quite difficult to get it to fluff up into the space without gaps which can cause condensation. It worked but we weren’t really big fans of it afterwards. At least it was local British, mainly Welsh, wool.

For the roof we were having to fill the joists from the underside of the roof. So we decided that wool would not stay put under gravity and that something more solid was required. We chose for hemp batts, made from hemp grown in East Yorkshire. These are much more rigid and could be cut quite easily with a specialist saw blade, however they still tried hard to fall out under gravity so we had to staple the last layer to the joists until we could install the air tightness membrane to hold them in place. If we were to build another house we would use hemp batts in the floors too.

 

Finally the windows and doors are triple glazed units made with wood frames covered in aluminium.