Hempcrete

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Construction block made from hempcrete

Hempcrete is a mixture of hemp hurds (shives) and lime (possibly including natural hydraulic lime,[1] sand, pozzolans or cement) used as a material for construction and insulation.[2] It is marketed under names like Hempcrete, Canobiote, Canosmose, and Isochanvre.[3] Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and consequently does not need expansion joints.[3]

However, the typical compressive strength is around 1 MPa,[4] around 1/20 that of residential grade concrete. Hempcrete walls must be used together with a frame of another material that supports the vertical load in building construction, as hempcrete's density is 15% that of traditional concrete.[5] (Despite the URL, the article does not mention the strength compared to concrete and the title appears to have been corrected.) Tests in Sweden showed disappointing thermal performance: "The hempcrete building system showed to have a thermal performance similar to that of passive houses in more southern climates. In the north of Sweden however the hempcrete building required up to 20% more energy than the passive house to maintain comfortable indoor temperatures." - This is speculative and based on a software simulation that a student performed for his university project that takes into account only the U values, not the thermal mass of hempcrete. [6]

Like other plant products, the hemp crop absorbs carbon dioxide gas as it grows, retaining the carbon and releasing the oxygen. 165 kg of carbon can be theoretically absorbed and locked up by 1 m3 of hempcrete wall over many decades.[7]

References[edit]

  1. ^ Allin, Steve. Building with Hemp, Seed Press, 2005, ISBN 978-0-9551109-0-0. (p. 146, 1st Edition).
  2. ^ "NNFCC Renewable Building Materials Factsheet: An Introduction". National Non-Food Crops Centre. February 21, 2008. Retrieved 2011-02-16. 
  3. ^ a b Priesnitz, Rolf B. (March–April 2006). "Hemp For Houses". Natural Life Magazine. 
  4. ^ "Tradical Hemcrete 2008 Information Pack" (PDF). American Lime Technology. Retrieved 2009-08-25. 
  5. ^ Flahiff, Daniel (August 24, 2009). "Hemcrete®: Carbon Negative Hemp Walls". Inhabitat. 
  6. ^ Ahlberg, Johan and Georges, Elza and Norlén, Mikael (2014) The potential of hemp buildings in different climates: A comparison between a common passive house and the hempcrete building system. Uppsala University, Department of Engineering Sciences.
  7. ^ "Tradical Hemcrete 2008 Information Pack" (PDF). American Lime Technology. Retrieved 2010-05-15. 

External links[edit]