Eco-friendly Homes Go Upmarket
Once the preserve of DIY alternative home builders, eco-friendly building materials such as mudbrick, rammed earth, straw bales and hemp are now being used to create the most luxurious (and sustainable) of homes.
Sustainable building materials are no longer exclusive to DIY homes constructed on communes tucked away in isolated locations. Across New Zealand we are seeing exciting, even super luxurious, homes being constructed from previously “alternative” building materials such as mudbrick, rammed earth and straw bales. And why not? Not only are these materials eco-friendly, they can also be aesthetically beautiful and create homes that are healthier and more comfortable to live in.
One eco-friendly building material that is exciting us with its potential is hemp. The versatile hemp plant (a relative of the more contentious cannabis plant) has been used for centuries to make rope and other practical materials, even clothing, and is now being championed as the ultimate eco-friendly building material – a high-performance, low-impact and contemporary building product.
As a building material, hemp does great things for the performance and livability of a home, its kind on the environment in its processing and is one of the super crops being hailed as part of the regenerative farming revolution.
Hemp used in building comes with many labels, including hemp-lime composite, hempcrete, hemp masonry and in situ hemp. The plant itself is quick-growing (over four metres in less than 100 days), requires no herbicide or fertiliser and acts as a nitrogen fixer, and its straight-forward processing adds little embodied energy to the final building product. It sequesters carbon dioxide while growing and continues to act as a carbon sink when mixed with lime to form a building material.
Hemp masonry is thermally efficient, providing good levels of insulation, breathable – which reduces internal humidity, and non-flammable, making it an ideal material for bushfire zones.
The woody stem, known as hurd, is crushed and mixed with lime and water in a process rather like making concrete. The most common system of hemp construction is for formwork to be erected on either side of a timber frame and the hemp/lime mix placed and lightly tamped down to remove air pockets. Inside, hemp walls can be finished with natural clay or lime render or left in their natural state to celebrate the unique textural effects.
On the exterior, hemp masonry needs to be rendered to make it rain-proof. However, the render must be breathable. Suitable lime-based renders are available from Australian Hemp Masonry Company, Ozhempand Rockcote, in a variety of textures and colours.
Rockcote also produces a smooth, glass-like render suitable for finishing hemp walls in wet areas.
Speedier construction methods, such as precast hemp/lime blocks, are available in some countries such as the UK, but not as yet here in New Zealand.
To date, very few hemp homes have been approved and constructed in New Zealand, but with so many advantages, and costs equivalent to more traditional building materials, we can only see this number growing as rapidly as the amazing hemp plant itself.
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