In August 2019, Professor Marton Marosszeky, Director at BCRC, Sydney, New South Wales, Australia conducted a fire test on a hempcrete lime rendered wall built from Australian Hemp Masonry (AHMC) products. The previously constructed hempcrete wall was rendered with 10mm of AHMC Hemp-lime Render. A week later a 600mm high pile of bush timber was piled up and ignited at the base of the wall.
The test was conducted to simulate an ember attack situation during bushfires where there is potential for a buildup of fuel at the base of walls. The fire was maintained for 1 hour and fully documented. No damage was observed in the 200mm thick, 10mm rendered hempcrete wall exposed to a 600mm high flame from a fire burning right against the wall for a period of 60 minutes.
Providing all other aspects of the treatment of any building built in a bushfire prone area are designed and detailed to comply with AS 3959, 'Construction of buildings in bushfire prone areas and a certified building process', 200-300mm hemp masonry, or hempcrete, can perform satisfactorily for use in bush fire prone areas to BAL (bushfire attack level) 40 when rendered with 10mm lime render.
In full scale laboratory fire testing to 1,000°C, the temperature 60mm below the surface of the exposed face did not rise above 100°C, the temperature of boiling water and far below the ignition temperature of pine which is over 400°C.
Flame-Resistant Hemp Blocks Survive Australian Bushfire
An Australian bushfire in 2022 put the spotlight on the fire-resistant properties of hempcrete blocks, offering a sustainable construction solution. There was no loss of life on Saturday, 5 February, when a mid-afternoon blaze swept through the village of Bridgetown (pop. 4,500), about 150 miles southeast of Perth, Western Australia.
However, the Hemp Squared Pty Ltd block factory located outside of town was destroyed in the fire. Founder/owner Iggy Van lost 90% of the company’s stock, but a stack of fully cured hempcrete blocks made prior to the end of December survived. “Interestingly, the blocks that survived were stacked on [wooden] pallets” Van said. “The pallets burned down, but the blocks did not”.
Partially cured hempcrete blocks were charred (front), but the fully cured hempcrete blocks (back) were undamaged by the bushfire.
Hempcrete is fire resistant because of the lime in the mixture. The combination of hemp, lime and water cures after about six weeks into a stone-like material that regulates temperature and humidity.
Hempcrete, or hemp masonry, homes are encouraged by the Australian government’s Department of Energy, as sustainable building solutions in a country where bushfires have destroyed thousands of homes causing billions of dollars in damage.
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8 January, 2025