The Californian fires are devastating and no doubt families will want to rebuild what was lost. There is a lot of talk on social media platforms, like by investor Bill Ackman who is looking to invest in AI technologies to predict and help drones stop fires. But sometimes, vernacular building and sound ecological practices can save the day before technology, in a space called low-tech.

Fire hydrants and water packed drones might put out a fire if caught in time, but disaster-proofing your future might be a sound and sustainable move. Hemp blocks, also known as hempcrete are already on the market and are eco-friendly and sustainable construction materials composed of hemp, lime, and water.

In a recent study scientists look at the fire behaviour and structural performance of hemp-based materials in varying formats. They tested raw hemp shives, hemp blocks, and non-load-bearing hemp block walls.

Researchers tested how various kinds of hemp reacted in fire safety and strength tests. 

The study found that hemp blocks don’t catch fire with open flames but rather just smolder slowly, producing very little smoke. In fact, walls made of hemp blocks stayed structurally intact for 2 hours during fire tests.

Tests conducted include cone calorimeter, bomb calorimeter, standard furnace, heat-transfer rating inducing system (H-TRIS), and small-scale elevated temperature material tests. Hemp shives exhibit ignition with sustained flaming, a relatively high heat release rate (HRR), and a relatively low critical heat flux (CHF).

However, the hemp blocks exhibited no flaming ignition, only smouldering combustion, and an HRR an order of magnitude lower. Hemp blocks and hemp shives produced minimal smoke. Hemp blocks charred, and associated discoloration zones have been documented. Tests indicate that limited structural capacity is lost up until 200 °C, whereas at 300 °C, the residual material strength is almost negligible.

Their conclusions were that the hemp block walls maintained their structural stability and integrity for 2 hours of standard fire testing. The ambient-temperature compressive strength of the hemp blocks was determined to be 1.0 MPa. This work is the first comprehensive study on the fire behaviour of hemp blocks and highlights their good performance, whereby they are likely to have a limited impact on fire risk in buildings.

Plastered walls will have a fire performance exceeding those reported in the study, the researchers say. The work was reported in the Journal of Building Engineering.

The research was led by Yohannes Werkina Shewalul and Richard Walls from Stellenbosch University, South Africa. 

Hemp, or industrial hemp, is a plant in the botanical class of Cannabis sativa cultivars grown specifically for industrial and consumable use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants on Earth which makes a great, hearty, sustainable fiber. It has taken nations years to recognize hemp as a viable building and material alternative because tiny amounts of the active ingredient of THC can be found in hemp.

Companies producing hemp blocks:

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