The roundhouse frame and roof was built by Australian Roundhouses; and Josh Proudman did the hempcrete walls and ceiling fit-out. The off-grid construction, home to Ken Leach and Sandy Martin, was completed in June this year after almost two years of planning and research. The actual build took 97 days, but a wait on materials and holidays extended the construction, Ms Martin said.

Mr Leach has been a member of the Alternative Technology Association, now Renew, since 1996. “I’ve had an interest in sustainability and the environment for a number of years, and it just followed on,” he said.

The roundhouse design has a 22-sided corrugated iron roof. The framework and materials used in the exterior and interior can all be offset in the environment. Ms Martin is creating one-off pieces to fit the interior. It is powered by 12 lead acid batteries that conduct energy from 14 solar panels on a shed roof. They power both the house and shed, Mr Leach said. “The amount of power we actually have is about 3KW hours,” he said. “I'm totally off the grid, so I don't have power bills.”

Adjusting to life in a sustainable house isn’t without its challenges. They’ve learnt to be smart with appliance use. Also included is a dry-composting toilet. The 300mm hempcrete walls maintain an even temperature all year and are more fire-resistant than traditional wooden-build homes, Mr Leach said.

The house, at 558 Redgrounds Heights Road, will be one of 200 such homes open to the public on September 16, 10am to 4pm, for Sustainable House Day.