The most sustainable building material on the market today is hempcrete. Hempcrete is considered a unique ‘bio-fiber’ that is composed of hemp shiv (hurds) and a mineral based binder (lime). The ingredients are combined with water where a chemical reaction takes place with the lime and shiv to form a solid substance. The process is referred to as bonded cellulose. Once thoroughly dried and cured, hempcrete reputed to be seven times stronger than concrete.
The binder in hempcrete does not merely fill voids within the block but instead coats the hurds so that they adhere to each other in all places where they touch. The process is entirely different than concrete or mortar. It forms a more dense and solid mass that resists cracks and fissures.
Hempcrete lacks the structural capacity of concrete and cannot fully support roof loads. It depends on wall framing and double stud to create form. The hempcrete does help prevent the studs from buckling or bending, but it is not sole support. However, its ability to increase load capacity is impressive. The Queen’s University in Canada performed hempcrete testing. They found that a two by six wood stud with 19.5 pounds per cubic foot of infill hempcrete could easily offer support three to four times the load compression of a standard stud wall. Hempcrete’s ability to support the wood stud and prevent it from bending is undeniable.
Unlike concrete block which requires sheetrock or wire mesh to support plaster, bonding agents, mud, or adobe, hempcrete insulation easily supports a textured surface. It is an ideal substrate for wall finishes.
Hempcrete insulation is very rigid and textured which makes it an excellent substrate for plaster finishes without any need for mesh or another bonding agent.
In a recent study undertaken by researchers in Canada, it was found that hempcrete is far more suitable for seismic prone areas than concrete. Hempcrete offers a far greater deformation compacity before it suffers any type of compression fracture. However, to receive such amazing results the composition and compaction at the time of manufacturing is critical.
Please consider these key points when thinking about hempcrete vs. concrete.