Hempcrete: is it competitive with today's construction tech?
Houses around the Southeastern U.S. have been built with a resurging construction material over the last few years: hempcrete, which is a simple mixture of hemp fiber, lime cement, and water.
The hemp fiber, one of nature's strongest fibres, is obtained by pulling the stalks or hurds from the cannabis plant with a decorticator machine or by hand. Keep that in mind next time you think about doing renovations.
Although it's not widespread in modern suburban America, hemp has been around longer than the human species has existed. It was used in a variety of applications in ancient Egypt, and archaeological remnants indicate that hemp concrete may have been used in housing thousands of years ago.
Hemp concrete is used by builders because it has strength when combined with traditional techniques used to make wood-framed buildings and houses, concrete block walls, and steel-framed structures. It can be poured around these standard frames to provide sturdy walls with several advantages over basic drywall and Sheetrock:
- Insulation: it has a good R-value at the right thickness, enabling it to stand up to hot and cold weather. This can substantially reduce the costs of household HVAC climate control and home maintenance compared to walls with fiberglass (glass wool) batt insulation.
- Durability: it can preserve wood frames by preventing termites from accessing the lumber. It is not as brittle as non-reinforced concrete, so it doesn't crumble like concrete blocks and drywall. Houses with hempcrete could last centuries instead of decades.
- Fire Resistance: like stone and brick, hemp concrete does not burn in forest fires.
- Humidity Regulation: the pores of hempcrete allow the hygroscopic lignocellulose fibers to absorb excess moisture from the air and release it in drier weather.
- Ballistic Properties: the material is able to withstand impact much better than thin metal sheets, lumber siding, and drywall. This protective property is beneficial in areas prone to hurricane and tornado damage. Hemp homes might also outperform their neighbors through other disasters, such as flash floods.
Will the value of hemp concrete justify its cost? What is the price per cubic foot?
More empirical data from residential builders, engineers, and designers could help prospective home buyers make informed choices about a material that has the potential to be economically viable and competitive with modern construction technology.
Photo by Scott Lewis.