Layered wall appearance on the hemp house being built in Nothland.
HEMP HOUSE
NORTHLAND Hempcrete is a relatively new building material that is turning heads in New Zealand because of its high-performance attributes, its sustainability and low environmental footprint, and the simplicity of the system which can be installed successfully by the owner. We are building the first Hempcrete house in the Northland/ Auckland region, and only the fourth consented hempcrete home in New Zealand. By Toby Ricketts
18
SPRING 2020
H
emp ‘shiv’, which is the inner woody core of industrial hemp plants, are cut into short lengths and mixed with a binder. This is primarily made up of hydraulic lime which is combined with water. When mixed it becomes porridge like in consistency, and is ready to place into the formwork to form monolithic walls of the house, both interior and exterior. Mixing only takes a couple of minutes (with the right hardware), and once the hempcrete has been placed, it is firm within an hour, solid within four hours, and fully cured within 6 – 14 weeks depending on temperature. Due to the location of our build we needed to construct our house on pole foundations, and so had to rule out heavier natural building techniques, such as rammed earth, mudbrick, or even light earth. Hempcrete is less than one tenth the weight of concrete (at 330kg per cu/m) so it was feasible to construct on a supported and braced platform. This is
the first hempcrete building on poles in New Zealand, and possibly the strongest, with 146 x 250SED poles and heavy duty bracing installed. It’s a strong building! We’ve chosen to build our house with Hempcrete as the benefits are many and varied; - Excellent insulation rating (R=5 @400mm, R=2.85 @ 200mm) - Moisture permeability – moisture can transit through the walls - Thermal mass – retaining warmth in winter, cool in summer - Fire-proof – will not burn - Rot and mould proof - Rodent proof - Amazing acoustic properties, both sound proofing and sound control - Carbon negative – actively sequesters carbon from the air in the lime hardening process
EARTHBUILDING MAGAZINE - www.earthbuilding.org.nz
