Hemp building a green future

By John Dvorak, hempology.org

The construction industry is one of the largest producers of greenhouse gases worldwide. Production of just one ton of Portland cement, the most common type, releases a ton of carbon dioxide (CO2) into the atmosphere. Fortunately, there is a ‘new’ concrete product made from hemp that not only sequesters CO2 during its growing cycle, but also has a carbon-negative footprint when used in construction.

Hemp concrete has lots of other beneficial properties, too. The hurds, which make up the inner part of the hemp stalk, are 40% cellulose. Mixing crushed hurds with lime and water creates a pulpy mixture that can be used for constructing floors and walls as well as insulating roofs. Hemp concrete is an excellent insulating material, comparable to standard skin- and lung-irritating, petrochemical-based, pink fiberglass insulation.

Three hemp houses were built in Asheville, North Carolina in 2010 by Hemp Technologies, Inc. Construction of the houses has generated a tremendous amount of media attention. Other hemp concrete projects are underway or planned across North America as builders seek ever-more environmentally friendly construction alternatives.

This process goes back to Roman times in Europe, and England, Switzerland, Germany and France have been documenting the environmental benefits of building with hemp for more than 20 years. Several homes were constructed of hemp concrete in Watford, England to compare energy usage to houses using standard building materials. Initial results show a considerable reduction in usage. The Adnams Brewery distribution warehouse in England was built of hemp concrete and, as a result, an $800,000 heating/air conditioning unit did not have to be installed, reducing electricity expenses by over $50,000 per year.

An area the size of a football field can grow enough hemp to build an average-size house. Hemp concrete is ‘breathable,’ or vapor-permeable, avoiding condensation problems like mold and rot. This also passively regulates the temperature of a structure, reducing heating and cooling demands. Hurds react with lime to create a fire resistant material that has been tested for one hour and 40 minutes without failing. Hemp concrete is recyclable. It can be crushed and used as fertilizer or reused for other building projects, so old houses can be recycled to fertilize the hemp that is used to build new houses.

Hemp concrete’s potential to become a hugely popular and profitable product could benefit those who get in on the ground floor of the industry. Unfortunately, the prohibition of hemp cultivation in America means hemp hurds have to be imported, resulting in a higher price than if it were grown domestically.