Hemp, wonder material
New forms of insulation can help reduce waste and improve thermal conditions in our buildings. Making use of hemp is a good place to start if you want to amp up the sustainability content of your home easily.
It’s mostly hidden from view and perhaps that’s why we don’t think of it as much. But insulation material makes up a large part of a building’s volume. Often, mineral wool is used. This is volcanic rock which is melted down and blown or spun into tiny filaments which are compacted to form the insulation.
A better way to insulate is by using hemp. A team of researchers in the USA is working on a type of hemp-based insulation that can also be used as a building material: hempcrete. For this material, the inner stems of the hemp plant – known as the shives – are combined with a biobased cementitious mixture.
While that cement-like mix is proprietary, it contains lime and various locally sourced minerals. The hemp fibres mix well as they have a high silica content.
The binding agent is combined with the mineral matrix (the shives) which results in a carbon-neutral (or even carbon-negative) material that is non-toxic and economical to use. It’s also a great insulator, with a thermal coefficient of 0,07 W/m2, which is similar to general purpose insulation material. To cap it off, hempcrete is lightweight – so much so that it floats on water.
Hempcrete isn’t viable as a structural building material though. Its compressive strength is too low, so it requires a supporting material, such as a timber or steel frame. Still, for light-weight structures and certainly for insulation purposes, it looks like the hemp plant is key to a winner.
Information via hemp product producers in the USA and in Australia.
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