Hemp used to tackle housing crisis

Simon Crittenden of Hills Carpentry and Building, Woodside, is designing and building compact, 'carbon positive', transportable homes using hempcrete - a building material made from the woody core of hemp stalks (hurd).

"We're using a waste water product to create a building product, when there is a shortage of building products," he said.

"Hemp is green and renewable, and it grows quickly, with only 120-150 days between sowing and harvesting.

"Plus one hectare of industrial hemp can absord 22 tonnes of CO2 while growing and a futher 108 kilograms per lineal square metre of external wall over 50 years, which we need to start doing more of for the future."

Mr Crittenden has been using the renewable product for four years, and while it may cost up to 15 per cent more than traditional building materials, he says hempcrete's long-term benefits far out weigh its higher initial cost.

"Hempcrete is very energy efficient, it regulates the temperature in a house," he said.

"In one of the houses we partially built with hempcrete - in summer last year it was 43 degrees Celcius outside and only 23 degrees inside in the kitchen at 3pm in the afternoon, there was no air-conditioning in the house hence reducing the need for it.

"It also doesn't allow mould to develop, it has no volatile organic compounds, so you're minimising noxious chemicals in your building, and creating a healthy home.

"It encases the timber frame and essentially petrifies the wood, so termites won't touch it, and it is the only building material currently on the planet that increases in strength during is lifetime due to its carbon absorption.

"It's also suitable for building in a flame zone areas as hempcrete burns at above 1200 degrees Celcius, whereas double brick can explode at 800 degrees.

"Plus it can't be overstated enough how pleasant and peaceful it is in a hempcrete house, it has a beautiful sense of well being."

Mr Crittenden has already built three homes in Mount Barker using hempcrete, completed one extension in Adelaide and a prototype of one of his compact, transportable display homes is in the works in the Adelaide Hills.

"I have a few clients who are looking to 'grow their own house' by way of an industrial hemp crop on their property and have me build them a hempcrete home - it's a real 'paddock to plate' building experience," he said.

So far, all the hemp hurd he has used has been imported from Europe - a costly exercise Mr Crittenden aims to solve by growing his own hemp in partnership with friend hills farmer Matt Dunn.

The two are growing a trial hectare of hemp varieties King G and Frog, fertilised by a special compost mix and irrigated by wastewater.

Sown in early October, the crop is expected to grow to 5-6 metres tall before being harvested in mid-March.

"We will harvest some King G seed off to grow more ourselves, but it will mainly be harvested for the fibre," Mr Dunn said.

Mr Crittenden said 1ha of a biomass hemp crop yields about 10t.

"You need about 6t to build a 280-300 square metre house," he said.

His compact homes have a 60sqm footprint, but had "no restrictions on height".

"It's the size of a 'granny flat' in the Adelaide Hills and Mount Barker council areas for those wanting a second dwelling on their property, which can double as a fire shelter," he said.

But by no means are these "miniature homes", Mr Crittenden said.

His display home has two bedrooms, two living areas, a kitchen and bathroom/laundry.

"Being of a modular style, there's also the ability to add more bedrooms, bathrooms and living areas if needed," he said.

"We build and transport to site for installation."

Mr Crittenden said the energy efficient nature of the home also made them suitable for off-grid living and short-stay accommodation.

But the partnership's hemp-to-home plan is not all smooth sailing, with questions still surrounding how the crop will be harvested and processed most efficiently.

"It's still an industry very much in its infancy," Mr Dunn said.

"There is full commercialisation of the industry in the northern hemisphere, but not in Australia yet, with the exception being what hemp growing guru Gavin Hopkins has been able to achieve by 'splitting the atom' in NSW.

"There is limited machinery out there to harvest hemp efficiently and it's an expensive investment.

"Plus we're only dealing with 1ha at the moment. We might be harvesting this by hand yet, or using a cutter bar on an excavator, and putting it through a woodchipper.

"Then we may bale it, while we sort out how we are going to process it."

Mr Dunn said they had the capacity to expand their cropping area to 100ha in the next three years.

"So we will need to look at investing in proper machinery in the future," he said.

"We may also be looking for investors to help expand our havesting and processing capacity."