So Why build with hemp?
In New Zealand we have two significant crises. Building homes with hempcrete can address directly and help mitigate both. The first is the global climate crisis and, the second is the very poor quality of so many kiwi homes (in terms of being damp and cold).
Impact Of The Global Climate Crisis
On New Zealand
Through the construction and heating/cooling of buildings, the construction industry globally is responsible for 25% of all carbon emissions. To address this statistic and the impact it has on climate change, the New Zealand Green Building Council is calling for all new homes to be carbon zero by 2030. This is to support the NZ government’s legislated commitment to our being carbon zero, as a country, by 2050. For new homes to actually be carbon zero, we need to be using construction materials that have a carbon zero footprint. We also need to construct buildings that require minimal heating or cooling.
Hemp As a Carbon Neutral
Negative Building Material
Hempcrete is one of the few building materials that can actually achieve a NEGATIVE carbon footprint. Hemp sequesters (takes out) significant amounts of carbon from the atmosphere as it is growing, and then continues to do so to a certain capacity once it is combined with its lime binder. One cubic metre of concrete creates around 150kg of CO2 One cubic metre of hempcrete sequesters approximately 300 kg of CO2 This means that every hempcrete home (or commercial building) is actually helping the planet by REDUCING the amount of carbon in the atmosphere, rather than contributing to it.
Heating or Cooling
Hempcrete homes require minimal heating / cooling because of the unique combination of hempcrete’s very good R Value AND its strong thermal mass performance (the ability to absorb heat and release it back into the interior space when the temperature drops). A straw bale home has a good R value, it has almost zero thermal mass performance; rammed earth houses have a great thermal mass performance but very low R value. Hempcrete is unique in having both a high R value AND good thermal Mass performance, meaning that heating / cooling of the home is minimal. This is good news for the home owner (comfort and electricity bills) and the environment (significant reduction of carbon emissions).
Thermal Value (R value) Achieved
In Hemp Lime Buildings
|Thickness in mm of Hemp lime Walling Materials||100mm||150mm||200mm||250mm||300mm||400mm|
|R Value achieved:||1.4||2.1||2.85||3.55||4.25||5.0|
|Thickness in mm of Hemp lime Roofing & Subfloor Insulation||100mm||150mm||200mm||250mm||300mm|
|R Value achieved:||2||3||4||5||6|
(R values table credit and a heap of fantastic hemp construction info:
No More Damp, Mouldy, Leaking
Hempcrete has a natural hygroscopic performance capacity. This means a hempcrete wall can absorb moisture from inside the building when there is an increase in humidity (caused by high rainfall, showering, boiling kettles & cooking, drying laundry inside, using gas heaters, costal air, high humidity regions). The hemp wall then naturally releases the moisture back into the interior space, when the internal humidity level has dropped. This means that condensation, black mould and a ‘leaky home’ are not possible in a hempcrete home. This greatly assists with minimising asthma and other respiratory diseases that are increasing exponentially in New Zealand. A hempcrete home is one of the healthiest buildings to live in. The outside of the hempcrete home does not need any cladding. To keep it watertight it is rendered with lime plaster. Having overhanging eaves is also a useful idea if the home is in a known high rainfall area.
Leaky Home Crisis!
The leaky home crisis in New Zealand is effecting around 90 000 existing homes and will cost at least NZ$48 billion to fix. (This figure does not include all the commercial and non-residential buildings that are also failing). Sadly, leaky failing homes are STILL being constructed in NZ today, 2020. One of the main causes of leaky homes is using cladding material which fails – and the NZ building code specifies that cladding on a new home only has to last 15 years!!! This is unsustainable and outrageous. A hempcrete house effectively fossilises or ‘cures’ so it becomes harder each year. Hempcrete buildings exist in Japan and India that are centuries old!!! With the impact on inhabitants’ physical and mental health, and the associated financial burden on our healthcare service, living in a damp leaking house is one of the biggest health and social issues we collectively face here in New Zealand today. Building homes in New Zealand with hempcrete, provides a real and achievable solution.
Hempcrete’s Fire Resistance:
Safety For You and Your Loved Ones
Hempcrete is a nonflammable building material (meaning it is almost impossible to catch fire). “A fire test was conducted in August 2019 by Professor Marton Marosszeky, Director at BCRC, Sydney, NSW. Built from Australian Hemp Masonry Company’s products, a previously constructed hempcrete wall was rendered with 10mm of AHMC Hemp-lime Render. A week later a 600mm high pile of bush timber was piled up and ignited at the base of the wall. The test was conducted to simulate an ember attack situation during bushfires where there is potential for a buildup of fuel at the base of walls. The fire was maintained for 1 hour and fully documented. No damage was observed in the 200mm thick, 10mm rendered hempcrete wall exposed to a 600mm high flame from a fire burning right against the wall for a period of 60 minutes.” (Credit: hempmasonry.com.au)