Did you know that there is a building material that is totally sustainable, environmentally friendly, mould, fire and water resistant, lasts for thousands of years and remains 100% biodegradable…but is not commonly in use in the US? Drum roll please…
Ladies and Gentlemen we bring you Hempcrete!
What is Hempcrete?
Hempcrete is a strong, durable building material made from hemp shiv (the tough woody fibres from the inside of hemp stalks) mixed with a strong hydraulic lime and a small amount of water. When it’s mixed it looks a bit like the mud & grass bricks that were the foundations of many a preschool snail farm - but if we’d had this stuff available as kids I reckon we’d have been more ambitious!
How is Hempcrete used?
Hempcrete can either be mixed on site or manufactured into bricks and transported. When it’s wet it can be poured around structural frames and used in exactly the same way as conventional concrete. Once hempcrete has dried it’s a hard, smooth, porous material that has a huge range of building applications including walls and floors.
Is Hempcrete as strong as concrete?
Yes and no…There’s a lot of air trapped in Hempcrete and as such it doesn’t have the same compression strength as concrete, meaning it’s not load bearing; walls would need a supporting frame.
On the other hand being made of plant material it’s not as brittle as concrete so once it has dried it will last indefinitely with no chipping or erosion.
Is commercial hemp growth viable?
Yes, yes, a thousand times yes! Check out these facts…
- One acre of commercially grown hemp produces pulp equivalent to around 4 acres of trees and can be grown from seed to maturity in 14 weeks making it easily sustainable.
- Hemp is easy to grow, doesn’t require chemical fertilizers or pesticides and grows so densely that weeds can’t get a hold in between!
- Hemp can grow in almost any soil conditions and climates. It could be a global resource.
- As well as using the shiv we can also use the outer fibres of the hemp stalks for manufacturing clothes and paper and the Omega-3 rich seeds as a natural and nutritious super-food. Scientists are even starting to recognise the benefits of hemp in the treatment of a wide range of conditions from arthritis to cancer – so there is no waste and incredible profitability.
Hempcrete and the environment
Hempcrete is carbon negative and 100% biodegradable!
- Hempcrete is high in cellulose, meaning it can absorb environmental carbon and retain it. So a hempcrete wall would be absorbing carbon emitted by the household and not returning that carbon to the environment! It absorbs and retains significantly more carbon than is required in its production.
- Hempcrete is made purely from naturally grown and quarried products. There is no chemical content and no waste – any hempcrete left over can be safely composted and will work its way back into the earth with no harmful side effects.
Hempcrete vs Concrete as a cost effective building material
(Sorry concrete, #loser)
- Hempcrete is a natural insulator and can be used to upgrade the thermal properties of older buildings. A house with hempcrete walls/floors would require no additional insulation and would cost far less than a conventional concrete build in terms of heating and air conditioning.
- Hempcrete can ‘breathe’ – it draws in and retains moisture when the atmospheric humidity is high and releases it again when the humidity is low. This ability to pass water in and out of the structure means that hempcrete does not suffer with ‘damp’. Concrete of course can absorb water but can’t release it so is prone to damp in humid climates.
- Concrete is not biodegradable and the production process is wasteful.
By this time I imagine you’ll be convinced – commercial hemp production is the way forward and hempcrete is the future for building sites all over the World!
So why isn’t Hempcrete more widely used?
Hempcrete is a growing trend in Europe, in the UK and even in a few US States but there’s a problem…
The Latin name for hemp is cannabis sativa (the translation of ‘sativa’ is literally ‘useful hemp’)and yes, it’s the same plant that can be harvested and used as the illegal drug marijuana.
Wait a minute…does that mean that you could get ‘high’ by licking a hempcrete wall? Or that if you built a fire and added hempcrete bricks the smoke would be psychoactive?
Sorry to disappoint you but no.
A commercial hemp crop is actually much lower in THC (Tetrahydrocannabinol - the psychoactive compound inmarijuana) than a crop cultured for drug use and the manufacturing process renders the THC completely neutralised. However, in many areas of the US the growth of any cannabis remains illegal.
Vast fields of cannabis plants waving (invitingly?) in the wind just isn’t the accepted norm…yet.
Globally we grow ever more desperate for a renewable and sustainable solution to our increasing need for resources. Commercially grown hemp is offering us that solution – now all we have to do is get over our fears and start making the most of this awe inspiring plant.