Industrial Hemp Explored as Alternative Building Material and Insulator

Originally published by: Builder OnlineAugust 22, 2014

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You probably haven’t thought much about using hemp to construct your next home, but maybe you should. It’s durable, lightweight, carbon-negative, and resistant to pests, mold, and fire—and it could potentially cut energy bills in half.

A natural, non-toxic building material, hempcrete is a combination of chopped hemp shiv, a hemp stalk by-product, and a lime-based binder. It’s quick to ramp-up: Only 2.5 acres of hemp are needed to supply enough hemp shiv to build a 1,250-square foot house, and it can grow up to 14 feet in 14 weeks. During that time, it absorbs high amounts of carbon dioxide while requiring no pesticides or herbicides.

Hempcrete has a range of potential applications, from wooden frame infill to retrofitted insulation. The material has been used for years in Europe to construct homes, commercial buildings, and warehouses. But because of its association with marijuana (though they come from the same plant, industrial hemp has THC levels below 1 percent, meaning it can't be used as an intoxicant), it has remained controversial in the United States.

Growing hemp has been illegal in the U.S. for decades; however, the crop's high value has resulted in that stance slowly changing. Some states have begun to reopen industrial hemp production for research purposes, though restrictions are still strict.

The benefits of building with hempcrete are numerous. While it is not load-bearing, it adds strength to building frames and actually grows stronger over time as it hardens. Its low density makes it extremely lightweight. It has inherent insulation properties, resulting in a minimal need for heating and air conditioning systems and reducing energy bills by about 50 percent. It is also breathable and regulates moisture and humidity, providing natural air filtration and preventing mold growth.

One of the main disadvantages to using hempcrete is the lack of builders familiar with using it. This, along with the fact the hemp must be imported, results in higher upfront prices.

Where to Find It
Asheville, N.C.-based Hemp Technologies, the builders of the first American hempcrete home, provides hempcrete building products and consults on hemp building projects. Along with standard hempcrete, products include hemp insulation batts, hemp brick sound insulation blocks, and a hemp-based particle board alternative.

Chicago-based American Lime Technology, a joint venture between U.S. Heritage Group and the U.K.’s Lime Technology Ltd, also offers a range of construction and insulation products, including pre-cast wall systems, and offers training to building professionals interested in learning how to work with the product.

As a finishing touch, Oregon-based Fibre Alternatives supplies Hemp Shield, the first U.S.-manufactured wood finish and deck sealer made with hemp oil. Non-toxic and long-lasting, it utilizes hemp’s natural mold- and pest-resistance to provide environmentally friendly protection.

Industrial hemp offers some exciting benefits for home building as a sustainable and functional product that is healthy both for the environment and occupants. Though U.S. restrictions may make it a reach for some now, it’s one to watch as the number of “hemp homes” grows.

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