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> Hempcrete, made from mixing woody hemp fibre (from inside the hemp stalk), with lime and water, is then pushed into timber frames by hand to build an insulati

by twic 7y ago

> Hempcrete, made from mixing woody hemp fibre (from inside the hemp stalk), with lime and water, is then pushed into timber frames by hand to build an insulating wall. So it's a reinforced lime mortar, rather than a concrete alternative. You can use it to fill space, but not to bear load. More practical and quantitative detail here: https://greenbuildingcanada.ca/2017/advantages-building-hempcrete/ https://greenbuildingcanada.ca/2017/advantages-building-hemp...

NeedMoreTea 7y ago
Curtain walling is used just about everywhere else, no reason it can't succeed in housing too. There was a Guardian piece about a hempcrete house just yesterday, with the hempcrete held in frames made from the hemp stalks and resin made from agricultural waste. Started out as a barn, so there was a steel structural frame to be filled in. The prospect of carbon negative building has to be a huge plus. https://www.theguardian.com/artanddesign/2019/dec/07/flat-house-margent-farm-cambridgeshire-hemp-practice-architecture-carbon-energy https://www.theguardian.com/artanddesign/2019/dec/07/flat-ho...
- ogrisel 7y ago
  Lime production is carbon intensive (heat + chemical C02 release from the limestone) and the hempcrete curing will take 50 years to fix back the second part. So it can be carbon negative (by fixing the carbon of the hemp itself) but only on the long term (50 years after production) and assuming that the heat used for lime production was from non-fossil source in the first place (which is not the case today: the cement industry typically produces heat by burning natural gas). The heat could be produced from burning green hydrogen (hydrogen produced by water electrolysis using renewable power) but as of today is still too expensive compared to using fossil fuels.
  - ogrisel 7y ago
    A simpler alternative to get carbon negative buildings is to use Cross-Laminated-Timber (CLT) to build both the frame and the walls themselves.
  - deleted 7y ago
    [deleted]
calibas 7y ago
I believe it can bear load, but it takes something like a decade to harden to that point. It's like very slow curing concrete.
shermozle 7y ago
I have a hempcrete extension on my house in Sydney. It's not load-bearing but it very effectively insulates. It's packed into formwork so there's no gaps or seams. This is in a city with mostly terrible thermally-performing buildings so, combined with double glazed windows (also rare in residential in Australia) we have an amazing house thermally. Regularly 10 degrees cooler than outside in Summer and the reverse in Winter. We originally were going to use another high-performance technical product to achieve the same. The cost ended up about the same. Hempcrete has higher labour costs and the technical product cost more but went up much quicker.

by twic 7y ago

NeedMoreTea 7y ago

Curtain walling is used just about everywhere else, no reason it can't succeed in housing too. There was a Guardian piece about a hempcrete house just yesterday, with the hempcrete held in frames made from the hemp stalks and resin made from agricultural waste. Started out as a barn, so there was a steel structural frame to be filled in. The prospect of carbon negative building has to be a huge plus. https://www.theguardian.com/artanddesign/2019/dec/07/flat-house-margent-farm-cambridgeshire-hemp-practice-architecture-carbon-energy https://www.theguardian.com/artanddesign/2019/dec/07/flat-ho...

ogrisel 7y ago
Lime production is carbon intensive (heat + chemical C02 release from the limestone) and the hempcrete curing will take 50 years to fix back the second part. So it can be carbon negative (by fixing the carbon of the hemp itself) but only on the long term (50 years after production) and assuming that the heat used for lime production was from non-fossil source in the first place (which is not the case today: the cement industry typically produces heat by burning natural gas). The heat could be produced from burning green hydrogen (hydrogen produced by water electrolysis using renewable power) but as of today is still too expensive compared to using fossil fuels.
- ogrisel 7y ago
  A simpler alternative to get carbon negative buildings is to use Cross-Laminated-Timber (CLT) to build both the frame and the walls themselves.
- deleted 7y ago
  [deleted]

calibas 7y ago

I believe it can bear load, but it takes something like a decade to harden to that point. It's like very slow curing concrete.

shermozle 7y ago

I have a hempcrete extension on my house in Sydney. It's not load-bearing but it very effectively insulates. It's packed into formwork so there's no gaps or seams. This is in a city with mostly terrible thermally-performing buildings so, combined with double glazed windows (also rare in residential in Australia) we have an amazing house thermally. Regularly 10 degrees cooler than outside in Summer and the reverse in Winter. We originally were going to use another high-performance technical product to achieve the same. The cost ended up about the same. Hempcrete has higher labour costs and the technical product cost more but went up much quicker.