BAL FZ Hempcrete Home 

They say good things come in small packages. That’s certainly true for the fondly named ‘Hempy’ – a small hempcrete house built on a block with the highest bushfire rating, BAL-FZ, in Blackheath in the Blue Mountains west of Sydney. 

Owners Kamil and Vercha wanted a warm and well-insulated house, like the ones they’d lived in in Europe. They also wanted to build with natural materials, so they engaged designer and hempcrete expert Kirstie Wulf, director of Shelter Building Design. The couple had a draft design for the house, which Kirstie finessed to refine the proportions, optimise passive solar performance and meet BAL-FZ standards. “It’s great to have clients who know what they want. Vercha and Kamil were passionate and involved in the project,” she says.  

The L-shaped house is set toward the back of the north-west facing site to bring in as much northern light as possible and to keep it further away from the most likely bushfire attack path. The internal space is 76 square metres, neatly housing two bedrooms, a bathroom and laundry along the rear of the block with an open kitchen, dining and living room taking advantage of north-east and north-west sun. This living space opens onto a deck with a large eave for shading in summer; the front corner of the eave is cut at an angle to let the winter sun in and accommodate an existing tree. “With the eaves and shading, we aren’t baking in summer, and the light in winter still reaches into the house,” Kamil explains. 

“We can’t see the hempcrete now that it’s rendered, but we can feel that we’re surrounded by thick walls. It’s very comfortable and cosy,” says Vercha. In fact, one small section of wall has been left unrendered and exposed to create an ‘honesty window’, offering a view of the fibre structure of the hemp.  

Vercha and Kamil used Tradical hempcrete from supplier Oz Hemp: a mixture of lime, hemp hurd and water. Hempcrete provides excellent insulation and thermal properties, keeping the house cool as the day warms up, and warm as outside cools at night. “The winters are cold in Blackheath, so it’s nice to come home to a house that maintains a fairly constant temperature,” Kamil says.  

The Tradical hempcrete is CodeMark certified and exceeds minimum requirements for BAL-FZ rated building. Being in a direct flame zone, the house couldn’t feature any timber externally, with the exception of the timber-framed windows and doors from Paarhammer, which are also BAL-FZ rated. Hempy is a small house so there aren’t a lot of windows, but these rigorously tested, Australian-designed and made windows (with German hardware) are still an investment. Kirstie designed and strategically positioned the windows to make sure each one serves its purpose. “Because they’re expensive, you have to think about each window’s size, placement and purpose: whether it’s for light, views or cross ventilation. It’s really useful to do that in any build,” says Kirstie. 

The need to avoid external timber can make decking a difficult issue in bushfire zones. Kamil and Vercha chose non-combustible fibre cement with a ceramic wood-look tile on top. It gives the impression of timber and meets the BAL-FZ requirement for no gaps in the decking (gaps are dangerous for ember ingress). 

The bushfire rating does not impose restrictions on timber use inside, though. FSC-certified spotted gum flooring and paulownia timber lining boards to the ceilings give a soft and natural feel to the space. Delicate timber trim conceals the junction between the roof and walls, curving with the hempcrete, and the timber flooring is cut to be flush with the rounded corners of the sandstone slab beneath the wood stove.  

With the hempcrete, insulation and double glazing, Hempy has a 7.9-Star rating, but would be rated even higher in a milder climate. “It takes a lot more to get to 7.9 Stars in the cooler Blackheath climate,” says Kirstie. Beautiful, comfortable, energy efficient and bushfire resistant, Hempy demonstrates that a house can be small and also functional and lovely. “A lot of thought has been put into making sure that things are not bigger than they need to be,” says Kirstie. “I think the message is slowly getting out that people really don’t need huge houses.”