Frequently Asked Questions
Is hempcrete environmentally friendly?
Hempcrete is carbon negative. A 300mm hemcrete® wall absorbs in its construction 40kg per m2 CO2. A typical brick and block wall emits 100kg giving a net benefit of 140kg. We use British hemp. Hempcrete is also recyclable at the eventual end of the life of the building.
How strong is hempcrete?
Hempcrete is not load bearing. In a wall the loads are supported by the frame around which it is applied. As hempcrete is lightweight and improves the strength of the timber it encases, lightweight frames and foundations may be considered. Our test cubes have given strengths of 1N/mm2 at 35 days and 2.4N/mm2 at 215 days.
Do we need any additional insulation?
No. Hempcrete is highly insulating. A low density mix can be used as insulation in roofs and floors or batts of insulation can be purchased for this application. A 300mm hemcrete wall has a U value of 0.2 but this is not very useful for comparison as it functions differently to mineral insulation products. As hempcrete also has a high thermal inertia it uses much less energy to heat
and cool than other construction methods with a similar U value. As you avoid the need to construct cavity walls or install extra insulation layers and may be able to omit completely a central heating system, this makes the building method good value for money.
We place hempcrete floor slabs over recycled foamed glass insulation to take advantage of both the insulation and anti-capillary properties of this product as there is no damp proof membrane in a breathable floor.
Can hempcrete be used all year round?
When building with lime it is always best to avoid winter works as lime based building materials will be damaged if allowed to freeze
before they are sufficiently cured. Hempcrete should only be placed outside if the temperature is 5oC and rising. Inside work can continue as long as heating is supplied.
How much experience have you got?
At the time of writing we have been involved with building two Department of Environment and Climate Change housing estate projects, 2 schools and numerous private houses, extensions and commercial buildings. You can trust us to bring the benefits of our experience in sustainable construction to your project.
Could you tell me the curing time of lime cret and can you put a standard wash sand and cement screed over it cheers BOB
There is a 7 week curing period for limecrete floors, please see our limecrete schedule in the limecrete section.
How do you calculate your U Values for the thickness of the Hempcrete Insulation?
Thanks
Dan
Please contact Graham about this via his email which is durrantgraham64 at yahoo.com