When I first spoke with friends about insulating the house with hemp in 2018 I got all those jokes about hemp that you can get when you are telling about it. But hemp is, alongside with cellulose and straw bale a real good insulating material. But first things first.
When we decided to insulate the house better, we first read a lot about insulation and insulation materials. I claimed that insulation between the rafters would be the best solution. This is usually done in Germany but insulating the bevel comes with a high price per m². In Finnish houses, especially rintamamiestalos, usually the floors are insulated. In our house this was done using a mixture of sawdust and straw while there was a lot more saw dust than straw. Saw dust was a by-product of the wood industry and therefore cheap and available. But its insulation value is pretty low. And it comes with another downside. It starts trickle away due to gravity. After some time parts of the house are not or not well insulated any more. Heat just disappears through the roof.
In the beginning we thought about insulating with cellulose. There are several products around and they can be blown in. We got some quotes from different companies but then realised that if we let the sawdust in we need to build a new structure for the floor as the space between the supporting beams was already taken by the sawdust. So in order to blow in the cellulose those new structure had to be build. Kind of a mess as the new floor would have been nearly 20 cm higher than the rest of the floor.
We paused and thought further and came to the conclusion that the sawdust must be removed. We got some quotes from different companies and then chose one close to us. We still hadn’t decided whether we would go for cellulose or something else. I was often referring to hemp and its good insulation value and was commenting on the cellulose and its treatment with Borax. We did know from Marja from Iso-Orvokkiniitty that there is a company around that sells cellulose that was treated with clay rather than the suspicious Borax.
But, at the end we decided to go with hemp.
There isn’t any big difference between cellulose or hemp. Hemp just feels like the right material for us. (Actually I wanted sheep wool, which is unfortunately impossible to get locally). We ordered the hemp from Hemprefine and started the preparation of the floor with industrial paper for wind protection in wooden houses. We got lots of helping hands from within the family – Thank you! - to lay out the paper and get the hemp prepared.
All the hemp is stuffed in and parts of the floor is also back in. We hope that with double the insulation value compared to saw dust the hemp will keep the house warmer through the winter time. It is now my turn to get the sensors in so that we can actually evaluate the temperature differences between ground floor, first floor, cold storage and the outside.
One and a half year later
In January 2020 we were living with new insulation for 2 winters and subjectively the house feels warmer. As we heat mainly with firewood an objective comparison is obviously difficult and of course the winter of 2019/2020 isn’t really what I would call a winter that can be compared to that of 2017/2018 or 2018/2019 at all.
In order to check our self made insulation we bought a thermal camera. We are still learning how to properly use it and especially how to properly read and interpret the image, but find the first pictures below.