Hemp - it's been used to make rope, textiles and clothes, paper and bioplastics, and hemp oil is used medicinally. And now, it's one of the newest materials to build houses.
Two such "hemp houses" being built on 25 acres (10 hectares) of land near Cattai Wetlands, north of Taree on the NSW Mid Coast, are nearing completion.
Barry Lambert AM decided on hemp as the material of choice to build the two houses on his land. It was a natural decision for him; Barry has been a passionate advocate for medicinal cannabis research since his granddaughter Katelyn was born with Dravet syndrome. Her life has been saved with the use of hemp extract, and Barry has been recognised as a medical cannabis pioneer in Australia.
As a result Barry became chairman of a company which grows hemp in Tasmania (he is no longer the chairman).
He decided to have the two houses built for two reasons. One, although he concedes two houses aren't many in the big scheme of things, was because of the current housing crisis. The second reason was to show people what hemp houses are like.
"I'm a community minded sort of person and I can afford to do it so why not do it? And why not do it so they're not like every other house?" Barry said.
The houses are definitely not like other houses. Both houses have interior feature walls that feature the exposed, natural hempcrete. The result is a very textural, organic appearance.
To highlight the natural waves in the hempcrete walls, a dye was used resulting in walls that are an artwork in themselves.
"We were trying to do a little bit of a Japanese influence where you have those scenes where the mountains just keep disappearing into the scene," architect Alan Smith said.
It is the first time builder Don Everingham has worked with hempcrete, and it is a continuous learning experience for all involved.
Carbon neutral product
Hempcrete is made from hemp hurds (the insides of the stalk of the plant), chopped up and mixed with lime and water. The resulting product is then put in by hand and tamped down.
"It's a great product," Alan said.
"It's termite proof. And it's breathable, so there's no issues with humidity and moisture, mould."
The walls are sealed with special breathable sealer, and if painted, again, with breathable paint.
The hempcrete itself is not a structural product. It is formed around the timber frame of the house.
"So it's an insulation product. And it's also a thermal mass product. Here, we're relying on this in winter to pick up some of the heat from the room and store it in the wall. And in summer, it'll take some of the heat out of the air and return it to the ground; sort of passive solar situation," Alan explained.
It's carbon negative. If everybody build with this we'd be in a much better situation.- Architect Alan Smith
One major benefit of building with hempcrete, particularly in rural locations, is that it is fireproof.
"I can put a blowtorch to it and it won't burn."
Invite your mates and save money
The cost of using hempcrete is comparable to other building materials. However, if you wish to hire a builder to construct the house, be prepared to pay.
Hempcrete is more suited, at this stage, to those who can gather a bunch of people to help them put in the hempcrete and tamp it down. It is very labour intensive.
"It's not very commercial from an investment point of view; you won't see people out there building hemp houses around the place. But if you're a home builder, get your mates around each weekend to help you out," Alan said.
For builder Don Everingham, "It's different," he said.
"I had a couple of guys who were only willing to do two days a week or three days a week, because of the fumes. And it gets into any sores, because it's lime.
"But now we know a few secrets about it, I'd do it again."
Alan, though, is a fan of hempcrete.
"It's carbon negative. If everybody built with this we'd be in a much better situation," he said.
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