Hemp is known for its use in the fashion and wellness industries, with brands like KITX and BEAR respectively utilising the benefits of hemp in their clothing and products, now this plant fibre is making its mark as a sustainable building fabric.
At last years BDA National Design Awards, a house in Mudgee, NSW coined the ‘Mudgee Hempcrete House’ won the Paul Dass Memorial Prize, a prestigious award given to a designer for outstanding achievement in building design, and the award for Best Residential Building. Within this house as the name suggest is Hempcrete.
Hempcrete is a lightweight bio-composite made of the inner woody core of the hemp plant, weighing about an eighth of the weight of concrete. The material is used as an insulator rather than for a structural element. The core of the plant is mixed with a lime-based binder to allow it to be formed into slabs. The Hempcrete walls in the Mudgee house comes from locally grown hemp, giving the property insulation that is breathable, avoiding condensation and moisture issues. One of the big positives of using hemp is that the plant itself and how it is harvested makes it a regenerative farming process.
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We spoke to Dick Clarke, the designer behind the Mudgee house and principal of Envirotecture who has 35 years of experience in the field along with a Master of Sustainable Futures degree on the topic of the effect of state and local planning instruments on the sustainability of the built environment.
EWP: What was the inspiration for the design?
Dick Clarke: Inspiration came from the client’s design brief which stressed a desire for natural materials and the need for bushfire resistant materials to deal with the risks of a rural property surrounded by bush
EWP: What other sustainable building materials or design features are incorporated into the Mudgee Hempcrete house?
DC: The long plan of the home provides maximum northern solar exposure to warm the home during the cold winters, generous overhangs provide the shading required of an area that can frequent top 40 degrees Celsius. A retractable awning over the northern deck gives the flexibility to provide sun or shade as desired during the shoulder seasons.
The ceiling of the dining room conceals the working mechanisms of the warm air transfer system, a series of off-the-shelf fans and ducts that pull heat from directly above the slow combustion stove and delivers it to the bedrooms. This system negates the need for any other heating systems beyond the sun and fallen timber that needs to be gathered for bushfire safety.
EWP: What positive impact does the use of Hempcrete provide when designing a house?
DC: Hempcrete improves the performance and liveability of a building in a huge range of ways. It is thermally efficient –it controls heat flows through the wall; it is breathable –it moderates internal humidity; it is non-flammable –it is safe and code compliant in cooking spaces and bushfire zones; it is long-lasting – provided the detailing and construction quality is good, and maintenance is carried out, as in any building type, it will last hundreds of years.
EWP: What is the main difference between traditional building materials and Hempcrete?
DC: Hempcrete is a natural and renewable resource, locally grown with excellent insulation values. It is one of those super-crops offering an incredible yield that is part of the regenerative farming revolution.
EWP: In your opinion, is there an increase in a want for sustainable materials to be used in new buildings?
DC: Absolutely, people are increasingly aware of the way their homes impact on the environment and reflect their ecological footprint. The demand for Hempcrete, however, is not only being driven by environmental concern, but also by a focus on health. People want homes that are healthy, comfortable and sustainable and hempcrete ticks all these boxes.
EWP: How much does it cost and is it comparable in cost to building materials that perform the same function?
DC: The home cost approximately $700k which is about 15% higher than a regular timber framed, fibre cement clad building, which would achieve the same level of bushfire resistance, but would not come close in terms of thermal comfort and sustainability.
EWP: Where can a person access Hempcrete and where is it grown?
DC: Hempcrete can be sourced from farms within four hours of most sites in Australia, all states grow hemp except the Northern Territory.
EWP: Any other sustainability trends in the building industry we can expect?
DC: There’s an increasing shift to prefabricated homes where modules are built off-site in factories and then shipped to site as whole units.
And even more excitingly, there’s growing interest in PassivHaus. Passivhaus involves creating homes with incredibly high-performing glazing, insulation and airtightness. Together with the use of a Heat Recovery Ventilation System, this results in thermally efficient buildings with minimal reliance on mechanical heating and cooling.
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