Hempcrete is one of my favorite building materials for many reasons. It’s actually quite similar to concrete, but it doesn’t require widespread chemical processes or the burning of fuel that release greenhouse gas emissions. It’s also naturally fire and mold resistant. It basically offers the sustainable building industry a bio-based product that is carbon neutral and that can be used in a wide number of building applications.
What is Hempcrete?
Hempcrete is the biocomposite that is made from mixing the woody core of the hemp plant with lime and water. It is extremely lightweight weighing only about an eighth of the weight of regular concrete. Hemp is a relative of the marijuana plant without the high concentrations of THC. It is one of the fastest growing biomasses on the planet with the hemp fiber and seeds ready for harvest in four months.
Is Hempcrete Legal?
Since hemp is a relative of the marijuana plant, a lot of people wonder if hempcrete is actually legal. Indeed it is my friends.
On December 12, 2018 the United States Congress voted to pass the Agriculture Improvement Act of 2018, more commonly referred to as the Farm Bill, and it officially took effect in January of 2019 meaning that farmers can freely grow hemp on U.S. soil. Across the Atlantic, hemp has faced less stringent legal complications so there are several European firms that have specialized in providing a wide range of hemp building products. As hemp continues to gain momentum in the United States, more local suppliers and manufacturers should begin to emerge.
Sustainable Benefits of Hempcrete
As mentioned above, hempcrete weighs only about an eighth of the weight of regular concrete. The lightweight nature of hempcrete can also help to reduce the embodied energy of a building by reducing the emissions associated with transporting heavy materials. Since industrial hemp can be grown in a wide range of climates and soils, it’s an excellent alternative as a local building material.
Hemp is a super resilient crop — it can tolerate droughts, insects, and diseases and doesn’t require any chemicals in its growth. Oh yeah, and it helps to sequester carbon.
Because of its fast growth, structural blocks and panels made from hemp and hempcrete could become an alternative to more traditional cement blocks and timber framing. This could reduce pressure on forests across the world and help us cut back on the estimated 15 billion trees that are cut down each and every year. Less deforestation would also lead to increased carbon capture, thus offering a natural way to combat global warming.
Hemp as an Alternative Type of Insulation
Increasing the insulation of our homes is an important strategy to improve energy efficiency. Unfortunately, studies have found that nine out of every ten homes in the United States are under-insulated, with about 75% of all homes relying on some sort of fiberglass insulation which is a mixture of plastic and recycled glass. The woody pulp of hemp, when mixed with lime (as a binder) and water, offers an alternative to traditional fiberglass insulation. Hemp fiber as a natural insulation material achieves as high as R-3.5 per inch and water vapor resistance factor of 1–2 µ. Fun fact, Prince Charles recently built a “ Natural House “ that relies completely on sheep’s wool and hemp insulation and is warmed by a single wood stove.
Building with Hempcrete
Hemp can be used in the manufacture of structural blocks and prefabricated panels for exterior walls. Unlike regular bricks or cinder blocks, these exterior wall products increase the R-value by incorporating thermal performance into the structural component of your home.
In general, there are 4 different methods being used for building with hempcrete:
1. Wet-mixed hempcrete pouring. Similar to building concrete walls, a standard slip-form is the most common for building hempcrete walls.
2. Bricks and Blocks. Think Lego. These are non-structural and used as wall infill/insulation. Once the framing is done, then the bricks are either stacked and mortared together inside the framing, or form the actual wall assembly.
3. Complete structural wall panels. These SIPs are essentially custom wall sections that are built with the hempcrete and structure combined and shipped to site complete.
4. Spraying Hempcrete. Similar to pouring hempcrete on site, the difference is industrial equipment is being employed. It’s said to be much faster and has a better insulating value than handpacked hempcrete, but the equipment is quite expensive and takes far more know-how.
While hempcrete, hemp insulation, and hemp building blocks certainly offer numerous advantages, keep in mind that there are certain construction requirements that must be followed due to the lightweight nature of hemp.
Originally published at https://www.linkedin.com.
