I’ve recently encountered people discussing the merits of hemp house construction over conventional techniques. The question for many homesteaders is typically this: how can I build a home that’s safe, affordable, and has an insulation factor that can handle the summer heat and winter cold? Most homesteaders want something they can build with their own hands that uses natural products instead of chemically-treated lumber, fiberglass insulation, and so forth. So when it comes to hemp house construction – is there a value?
Hemp is a fast-growing plant of the Cannabis sativa family that’s widely known today for its role in the production of medicinal CBD oil. Hemp seeds have also become a popular “superfood” enjoyed by many for their nutritional value. The industrial hemp we’re discussing is not part of the health, healing, or getting-high side of things, however. Our focus is on the plant stems.
Hemp stems are comprised of tough fibers from which a variety of products such as ropes, textiles, shoes, and jewelry are made. Industrial hemp is also used to make animal bedding, bioplastic, insulation, and biofuel.
Below is an example of tough hemp stem fibers:
When hemp stems are processed for their fiber, some parts of the stem are left behind basically as scraps. This material is referred to as hemp hurds or shives. And it’s the hemp hurds that are used to create building materials.
Using Hemp in Construction
Hempcrete or Hemplime is bio-composite material, a mixture of hemp hurds (shives) and lime (possibly including natural hydraulic lime sand, pozzolans) used as a material for construction and insulation. It is marketed under names like Hempcrete, Canobiote, Canosmose, and Isochanvre.
Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and, consequently, does not need expansion joints.
Hempcrete is a natural building material. It is breathable and has excellent thermal qualities in construction applications.
The image below shows a Hempcrete fill used in the construction process:
Hemp Construction In France
Hempcrete has been used in France since the early 1990’s to construct non-weight-bearing insulating infill walls. Hempcrete does not have the requisite strength for constructing foundations and is, instead, supported by the frame. France continues to be an avid user of hempcrete where it grows in popularity annually.
Hemp Construction in the United States
While hemp may be the desired choice over concrete products here in the United States, most locations require permits to purchase hemp-based products or bi-products. Industrial hemp agriculture is also closely monitored in the United States and is typically restricted to plant varieties with low THC concentrations. Since THC is the psychoactive property of cannabis, this restriction ensures hemp grown for industrial purposes will have no adverse side effects on humans.
Properties Of Hempcrete Construction
The typical compressive strength of hempcrete is around 1 MPa (or around 145 Pounds per square inch). That’s about 1/20 of residential grade concrete. Therefore, hempcrete walls must be used together with a frame of another material that supports the vertical load in building construction.
Although hempcrete cannot be used as a replacement for traditional concrete blocks, it is a low-density material with some “give.” Since hempcrete resists cracking under movement, it is highly suitable for use in earthquake-prone areas.
Like other plant products, hemp absorbs CO2 from the atmosphere as it grows, retaining the carbon and releasing the oxygen. Theoretically 165 kg of carbon (or 363 pounds) can be absorbed and locked up by 1 m3(or 264 Pounds) of hempcrete wall during manufacture. Keep in mind, like most things related to heating and air and insulation, it’s in BTU’s or British Thermal Units.
This video from National Geographic provides more great information on using hemp in construction projects:
The Benefits Of Hemp And Hempcrete Construction
Although hempcrete is not a one-for-one replacement for traditional concrete, using hemp in construction projects does have some great benefits:
1. Hemp Stops Carbon Emissions In Your Home
Hemp is the only building material that actually removes carbon from the air. Other methods of insulation, like fiberglass, have a significant carbon footprint through their “off-gassing” properties. Hemp, on the other hand, cleans the air and reduces the carbon emissions we create in the course of our daily lives. Using hempcrete, in essence, turns your entire building into an air purifier.
2. Hemp Is Safer For Those With Environmental Allergies Or Sensitivities
The products used in and around our homes can have a tremendous impact on our health and our lives, and not always in a positive way. The use of chemical-laden building materials can literally make us sick. Hemp can help.
Besides the air-cleaning properties noted above, hemp is also a clean, non-toxic plant because it requires little to no pesticides or herbicides to grow. Hemp is harvested and processed in a safe manner without the use of harsh chemicals. Using hemp in your home construction reduces the toxic load from new building materials to help you and your loved ones breathe easier.
3. Hempcrete Breathes Well
Speaking of breathing, hempcrete does some of its own. Due to hemp’s porosity, it can pull excess water from the air when it’s humid and release that moisture when conditions are more arid. Hempcrete, as mentioned earlier, can sequester carbon, but it can also absorb a substantial amount of heat and humidity when it’s hot. And we think that’s pretty cool!
4. Hempcrete Is A Full-Use Product
Hemp is typically grown for its seed or fiber, which means the hemp hurd left behind after processing is basically a waste byproduct. Turning the hurd into hempcrete, however, means the entire hemp plant gets used. And less waste is pretty much always a positive thing.
5. Hempcrete Adds Strength
Even though hempcrete is not generally used for framing, its can definitely improve the structural integrity of a building. Hempcrete, unlike traditional concrete, has the unique advantage of being both strong and flexible. When it is used around studs, for example, it can prevent them from buckling and bending under significant loads. And, as previously stated, it can add some vital “give” to buildings in earthquake-prone regions. Hemp can truly be the backbone of a structurally sound home.
Hemp House Construction – There Is A Value
With these benefits, it’s no surprise hemp construction is growing in popularity. Building with hemp provides a number of unique qualities traditional building materials simply can’t match. I anticipate the use of hempcrete will continue to expand as the plant itself becomes more widely accepted. Would you build with hempcrete? After all I’ve learned about it, I surely would!