Acknowledged Challenges, Questions & Unknowns
Hemp hurd processing is currently available to US markets from the Netherlands, China, and a few small scale processors in the US and Canada. The embodied carbon of hempcrete could be greatly reduced if hurd processing and binder formulation were made locally or regionally available.
The various growth habits and varieties of hemp present different processing challenges. Tall plants that are harvested for fiber are the easiest to process for hurd. Bushy varieties grown for seed require a different processing method; these stems may be more suitable for paper and other products
Natural Hydraulic Limes (NHLs) are not typically mined in North America, as there have been few uses for them before.Sources of naturally occurring hydraulic limes are not well studied or documented in the US, though they may exist wherever ancient sea beds were exposed to volcanic activity. Alternatively, correct proportions of silicates and other mineral additives may be formulated to mimic the NHLs of European usage. (Additives are currently available in Europe.) The contents include commonly occurring minerals in the form of clay, silicates/alumina, and ashes.
Proprietary blends of hempcrete binder are available in the US. Price and quality need to be evaluated for practical use.
Hempcrete properties vary depending upon method used to build. Though hand packing can create inconsistent densities, it hasn’t been shown to affect performance.
Studies indicate insignificant performance gain between 9”(22cm) and 12”(30cm) walls in the UK.
Studies need to be conducted to validate properties of hempcrete, and building codes adapted, so that municipalities can permit these buildings. Criteria needs to be adjusted towards performance objectives rather than other industry prescribed conveniences.