Learn about Hempcrete Walls

Hempcrete is a solid material made from mixing industrial hemp fibres with a lime-based binder. The mixture is packed into forms and left to cure and harden. Hempcrete is a wall system that requires structural support, such as wood framing, to hold the weight of the roof and upper walls. The hempcrete itself becomes harder over many years, as it gradually absorbs carbon dioxide and turns to limestone. Hempcrete walls can be built in place by packing the hempcrete into forms, or made by stacking prefabricated hempcrete blocks that have their own internal structural support. Hempcrete has an R-value of about R2.5 to R3 per inch.

Look for local hemp products. In the North American market, hemp is legally grown in Canada. Otherwise, it can be imported from outside of North America. Consider your options for formed-in-place or prefabricated blocks. Some hempcrete blocks are available up to 16 inches thick, for an R40 wall.

Hemp is a renewable agricultural product that stores carbon dioxide as it grows, and takes very little energy to produce. The binders are also lime-based and don't require the high-emission Portland cement that concrete does. Hempcrete does not emit volatile organic compounds (VOCs) and is resistant to fire, insects, and rot. Hempcrete is also breathable to water vapour. On the down side, hempcrete's R-value per inch is not very high (R2.5 to R3 per inch), so you have to build a thick wall or add another layer of insulation.

Archaeological chemists believe that hemp and lime plaster has helped preserve the ancient paintings in the Ellora Caves, a complex of Buddhist temples in India, for 1500 years. The temples' hemp-coated walls have stood the test of time much better than neighboring temples that don't have hemp plaster.