“The mattresses that Zac will sleep on, they’ll be completely plant-based, natural hemp-based mattresses,” Bakker said.
Joost Bakker and Zac Efron on a flat roof at the home of Bakker’s mother in regional Victoria.Credit: Joost Bakker
Insulation, curtains, rugs and internal walls will be made of hemp, he said, as will the joinery in the kitchens. This is a technique that featured in an award-winning design for Woodleigh School on Melbourne’s Mornington Peninsula, co-developed by Bakker.
An example of hemp joinery at Woodleigh School on the Mornington Peninsula.Credit: Earl Carter
For Efron’s build, there is potential for the washing machine and dryer to be made partly from hemp, and battery technologies that use hemp are being considered.
“So we’re really using it in so many different ways throughout the building,” Bakker said.
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Industrial hemp is a form of cannabis that has very low tetrahydrocannabinol (THC), the component in cannabis that makes users feel high. Laws associated with hemp in Australia changed in 2017, meaning humans could consume hemp food products and industrial hemp could be grown for seed supply and for fibre.
Professor Rachel Burton, who specialises in plant science at the University of Adelaide, said the hemp industry was growing. Despite hemp not being widely used yet, she said there was potential for whole houses to be built out of the “long-lasting” product in future.
“Hemp is a crop that essentially grows quite fast, but it fixes carbon as it grows. So the material that you end up with is carbon-neutral,” Burton said. “It’s sustainable … in terms of the Australian landscape, it’s fireproof.”
In construction, hemp can be used for flooring but is mainly used to build walls, Burton said. A part of the hemp called the “hurd” is mixed with a binder, generally lime, to create a mud-like blend that is put between boards.
“You just pack it in, and then you just let it dry and then take the boards off, and essentially you have a wall,” she said.
Hemp bricks are lighter than conventional bricks.Credit: Joost Bakker
For Efron’s house, Bakker has worked with a Victorian block maker to create hemp bricks that don’t need lime, a product he said was often mined.
Instead, they are using oyster shells to bind the hemp to create bricks that look like Besser blocks. They are pricier than conventional brick, but may speed up construction since they are lighter.
“You get a really beautiful block,” he said. “They’re great because they pull in pollution from the atmosphere.”
Bakker estimated they would need 2200 hemp-based blocks for Efron’s home.
Oyster shells are being used to make hemp bricks for Efron’s home.Credit: Joost Bakker
Burton said the lack of processing facilities was slowing the use of hemp in construction. Other experts say builders need more training and education.
“There’s quite a lot of work to advertise the benefits of hemp … and as builders get more familiar with it, I think it will be incorporated,” she said.
“I’m hopeful that it will because … we have to start looking at different building materials.”
Sara Wilkinson, professor of sustainable property at the University of Technology Sydney, said as hemp was a low-carbon material, it was more sustainable than conventional materials like brick.
“Zac’s greenhouse” is slated to be finished by September 2026, Bakker says.Credit: Joost Bakker
“Given the large environmental impact of our conventional building materials – these low carbon sustainable materials are much needed,” she said.
As for Efron’s hemp-forward home, council has approved plans and foundation work has been done, said Bakker, with the “actual build” to start in February. Bakker intends September completion.
All internal walls are designed to “pull in pollution and breathe”, Bakker said, adding that even the floor was designed to be grounded.
“When Zac walks barefoot throughout his building, he’s always connected to the earth’s magnetic field.”
