Hempcrete – A Great Green Building Material
The word hemp often raises eyebrows given its relationship to the stuff people like to smoke, but hempcrete is a different side of the plant that makes a great building material.
Hemp is a form of marijuana that can’t be smoked for a high unless you are ready to smoke a few hundred bales of it. Instead, the material has long been used in everything from textiles to building materials. It is illegal to grow hemp in the United States since it is associated with marijuana and has many industrial groups lobbying against it. It is legal, however, to import it and use it for construction materials among other purposes. This is where we get hempcrete from.
What is hempcrete? As the name suggests, it is a hemp form of concrete. The exact ingredients vary a bit by brand, but generally are comprised of ground hemp stalks, water and lime. These are mixed together just like concrete using the same concrete mixer. You know, the machine that looks like a tilted bowl and rotates.
The resulting hempcrete is applied usually using forms of one sort or another. The hempcrete takes roughly a day to set firmly. It should then be allowed to cure for roughly 10 to 14 days to allow it to fully set. At that point exterior materials can be applied to the hempcrete walls. The real beauty of this application is the wall will last between 700 and 800 years. The lime in it also repels insects. Finally, the hempcrete is very fire-resistant.
The cost of using hempcrete is definitely more than traditional building materials in the short term. How much depends on the type of building, but it can cost 10 to 20 percent more than a traditional home. The costs can, however, be deferred in some ways. Initially, you’ll need less lumber with a hempcrete wall. Second, the home will be well insulated and use as much as 80 percent less energy when it comes to heating and cooling. Finally, most insurance companies will give discounts on home insurance policies given the fire resistant nature of the hemp.
Does hempcrete have a bright future as a green building material? Yes, but it will be limited in the United States until the relationship with marijuana is understood and disregarded as it should be.