Hempcrete: Eco-Friendly and Unique

September 28, 2015
November/December 2015
This online-only article is a supplement to the November/December 2015 print edition of Home Energy Magazine.
Click here to read more articles about Building Envelope

Using hemp as an insulator might seem far-fetched. Laughable even. But this green sustainable material just might be the answer to many builders’ problems. Here’s why you should give it a chance.

Hempcrete insulation is a mixture of hemp hurd (the inner woody core of the hemp plant) and hydrated or hydraulic lime. The resulting substance can be mixed with either cement or more lime to increase its strength. The more hemp in the mixture, the lighter the resulting substance, which makes it ideal for insulation.

Hemp is about as green a material as it gets. Ideal for the environment and posing no risk to people’s health, hemp is carbon sequestering, which is even better than carbon neutral. It is also incredibly sustainable; hemp is one of the fastest growing crops in the world, making it a much more plentiful resource than timber. Even the waste from hempcrete is green, and can be used as mulch in a garden.

Untitled The first part of a hempcrete wall completed. (Hempcrete Australia)

Untitled Hempcrete installers work on a training wall. (Hempcrete Australia)

Why Hemp? Hempcrete?

The hemp in Hempcrete is a good insulator because its pore structure allows it to regulate temperature better than most other building materials no matter what the season. In the summer, it regulates indoor humidity, and in the winter, it makes for a cozier indoor temperature. As long as it is installed above ground, hempcrete is also fireproof, waterproof, and rot-proof. For standard wall insulation, hempcrete will generally have an R-value of 2.5 per inch of thickness.

Hempcrete is not structural material, and requires a load bearing frame, but it is malleable enough to be blown in or tamped in to fit a form. Once shaped to the form, the hempcrete will set fairly quickly, and the form can be removed. The hempcrete will continue to harden and set. The result is a permanently airtight envelope. Hempcrete is simple to work with. It doesn’t have to be paired with layers of different building materials. And if it is paired with a small amount of structural timber or steel, these can be encapsulated in hempcrete instead of being layered on top of it or underneath it. Hempcrete is efficient and easy to maintain.

Green Built

James Savage, a former Wall Street analyst, built his company, Green Built LLC, around the idea of using hemp as a sustainable building material. After witnessing the toxic trailers people were forced into after Hurricane Katrina, and the devastation after the earthquake in Haiti, Savage decided that a change needed to be made. That change would come in the form of a nontoxic and sustainable material that he hoped would better people’s lives all over the world.

Savage located the company home in his native New York State. With hot, humid summers and very cold, snowy winters, the Hudson Valley was the perfect testing ground for temperature-regulating hemp insulation.

At first, he didn’t see much interest in hemp-based insulation. But in the last several years, Savage is starting to see a change in the way people view hemp. “I feel that we’re looking at an opportunity to change the way people build, and to move toward healthier and more environmentally friendly homes using hemp,” he says.

Green Built is currently designing a tiny net zero energy house showcasing hempcrete. The house will be tiny, by industry standards, but it will eventually expand to accommodate a growing family or even a small community. “Next spring we expect to put this house on wheels and take it around the country so that people can experience it firsthand and really understand what we’re doing,” Savage says. “We’re very excited about it.”

The Northeast was where Green Built got its start, and in the Northeast it shall stay, for the time being anyway. The historically rich Northeast is full of old masonry buildings in need of repair, and more specifically, in need of good insulation.

Hempcrete is the perfect solution. Some types of insulator, such as fiberglass batts, would only create new problems, with vapor barriers so rigid that they cause moisture to build up inside the wall. Preventing this moisture buildup requires adding layers to the wall assembly to allow moisture to escape. Hempcrete on the other hand, allows the building to breathe because it is more permeable than other insulators.

So what’s in store for the future of hempcrete? Only time will tell. In the meantime, Green Built and other small companies will be educating the world on the underdog building material, one tiny sustainable house on wheels at a time.

Elena Gardner is an information technology and services professional from Scottsdale, Arizona, who is currently the graphic designer at A Bit of Help, Incorporated.

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