The development of a modular construction method for industrial hemp could see it replace the low-performing, high-embodied energy materials used in the walls, floors and ceilings of large-scale Australian residential and commercial buildings.
Envirotecture director and Australian Hemp Masonry Company board member Dick Clarke said industrial hemp was “very applicable to all building types and building scales” with its low-embodied energy, carbon sequestration abilities, excellent insulation properties and ability to handle humidity.
In addition, industrial hemp requires little or no irrigation, minimal fertilisers, has no significant pests and grows densely, providing farmers with the potential to harvest two or more crops a year.
A huge body of work is coming out of France where they are using industrial hemp for ceilings and flooring. European car manufacturers are using hemp bast (long fibres) to produce car interior panels. While the Australian construction industry is mainly focused on using industrial hemp in residential wall construction, Mr Clarke cited one example of a Leichhardt ceiling installation that successfully met aircraft acoustic requirements for inner west Sydney.
However, research and development is focused on finding new techniques, as construction methods for industrial hemp are still fairly limited. Presently, the hemp is mixed onsite and placed between forms to set for 24 hours. Then the curing process begins. While the bulk of the curing can be done in 28 days, it can take up to three months.
“That kind of construction system is never going to win over the large-scale multi-storey buildings,” Mr Clarke said. “It’s just too labour intensive, too slow and requires too many people doing things onsite.
“What needs to be done is finding ways of speeding up the curing process and then at the macro scale finding ways of getting reinforced resources to interact with the aggregate nature of the material so that it can be pre-formed,” he said. “So when that little issue gets resolved, the volume of hemp that can then displace other lower performing, higher-embodied-energy materials like concrete, wall panels and various oil-derived plastic-based foams, that’s when a whole new ballgame starts.”
Mr Clarke said the long-standing prohibition that failed to distinguish between different species had hindered the industry.
“They just lumped all the cannabis plants in together,” he said. “Industrial hemp is a completely different kettle of fish from the medicinal/hallucinogenic strand. Hundreds of years of development of the technology just stalled and skills were lost and forgotten… Prohibition really created an unfortunate environment that the industrial hemp industry is still trying to shake off.”
Change is underway with the formation of the Australian Industrial Hemp Alliance last year and a mounting body of evidence that shows industrial hemp is experiencing a global resurgence. Work is underway to produce an Australian Standard for industrial hemp construction techniques with the assistance of the Cooperative Research Centres program, UNSW and high-level technical data and compliance from the UK.
Mr Clarke said education was one of the main barriers to broader acceptance and use of industrial hemp beyond the single-storey residential market.
“There is no imperative to achieve a higher level of compliance to steer people towards hemp,” he said. “So general awareness in the industry and with consumers – that’s a slow process because we have to grow supply and demand at approximately equal rates.
“We the industry can introduce people and educate them about high-performance, low-impact materials, [but] it’s mainly people who are well informed or are already enthusiasts for high-performance buildings that would choose it.”
For industrial hemp to be used in the scale of buildings that attract Green Star ratings or similar, the labour intensiveness of the material must diminish.
“There is nothing to stop them using it but you would need to make the numbers work before somebody could reasonably expect to send a larger commercial or public building down that route,” Mr Clarke said. “We have intentions of seeing that happen but the cost of construction in Australia demands efficiency; it’s difficult to get materials that are man handled into a building of any scale.”
The Australian Industrial Hemp Alliance is facilitating communication with regulators and bringing the industry together to communicate to the market.
“The industry needs to see itself as a whole and work together with the alliance to grow the whole market and be collaborative in their approach within the realms of free-market competition,” Mr Clarke said.
For more on the industrial hemp industry, see Hemp Building in Australia – where it’s at and where it’s going: an interview with Dick Clarke at a hemp building workshop in February.