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Hempcrete – Australian Hemp Masonry

Hempcrete House - Nick Sowden

Recently completed AHMC hempcrete construction in Sydney- Acoustic prototype housing.

Hempcrete

Construction from hemp lime composites is a new emerging technology that has has developed from ancient practices; It has been practiced for a few hundred years in Poland and Austria, 25 years in France and the last ten years in the UK and Australia. It is refered to as Canobiote, Canosmose, Isochanvre, Hemcrete, Hempcrete, Hemp Masonry or Hemp lime composite construction.  Hempcrete or hemp masonry gaining recognition as an efficient carbon neutral form of construction and is being increasingly used in the construction of individual homes and social housing schemes as well as in commercial buildings.

In 2002 we began doing research with the University of NSW to develop an Australian hemp lime composite building material. We developed AHMC propriety binders for hempcrete construction, hemp lime insulation and hemp lime renders. We are now ready to supply materials to the Australian Market.

Between 2009 -10, the UK Government invested £6.3m under the Low Carbon Investment Fund (LCIF) to support the construction of 283 low carbon affordable homes built with a range of innovative, highly insulating, renewable materials. They further funded a 2 year monitoring project and report. The conclusions were published in the proceedings of the 1st International Conference on Zero Carbon Buildings Today and in the Future, Birmingham City University, 11-12 September 2014:

“We believe that hemcrete has considerable potential for transforming the UK construction industry. The stable internal temperature and relative humidity lead to reduced reliance on mechanical systems, and to their lower installation and running costs. The stability of internal conditions has a considerable positive influence on thermal comfort. The negative embodied carbon facilitates substantial long-term carbon emissions savings and goes a long way towards achieving the future UK carbon emissions targets. Overall, we need more projects like this, and a closer collaboration between designers, developers, users and researchers from the early stage of the project.”

Hempcrete is a highly sustainable, low-embodied energy product requiring no kiln baking and it has excellent thermal insulation properties. It is a carbon positive material; it takes more carbon out of the atmosphere than it adds. These characteristics recommend the material in the context of legislation such as Basix and the expected development of further legislation related to energy consumption and greenhouse gas emissions.

While early hemp lime building research projects suggested that hemp lime masonry was 10% more expensive to build with than conventional masonry, a standard 3 bedroom home completed at the National Non Food Crop Centre in the UK for just £75,000 has proven that hemcrete can be used to build affordable homes on a large scale.

Since the Suffolk Housing project, further projects have been built in the UK including the Adnam’s Brewery and Distribution Centre Building in Southwald. The walling of the 2400 sq metre brewery and distribution centre incorporates a number of hemp lime products, as does the associated commercial vehicle maintenance facility.

Adnams Brewery Commercial Hemp project

The Adnams Brewery Distribution Centre in the UK was built using Hemp masonry blocks.

The choice to build the Adnam’s Brewery Building from hemp masonry rather than conventional masonry meant that 500 tonnes of CO2 emissions were saved during the building process as hemp lime captures carbon from the atmosphere and locks it into the fabric of the building. According to Prof Woolley, the warehouse development “has catapulted this environmentally friendly technology into mainstream commercial building”.

In 2011, the Triangle Project in Swindon a social housing project including 16 two-bed houses, 13 three-bed houses, 7 four-bed houses, 4 one-bed apartments and 2 two-bed apartments was completed. These buildings and a number of other hemp homes and a range of sustainable homes were assessed over a 2 year occupancy period through the UK’s Renewable House Monitoring Program.

The report released in 2015, showed that the consequent reduction of heating plant size and of the corresponding energy consumption and carbon emissions could be in the range between 50% and 80% lower than in buildings with conventional brick and block construction insulated to the same U-value as the hempcrete construction.

The Report also recognised the lower energy demand in-use, combined with the negative embodied carbon footprint (carbon sequestration potential) of the hemcrete structure as  -4.3 tonnes CO2 , as compared with +10.7 tonnes CO2 for brick-block house of the same dimensions.

Overall hempcrete is a very low embodied energy product. While lime production does have a significant carbon footprint, the fact that the building material contains such a high proportion of hemp means that this is more than offset. There is no kiln baking in the production of the final product, further contributing to this being a low embodied energy product.

  • termite, pest and mould resistant
  • durable (weather-resistant)
  • low thermal conductivity (R value = 4.2 for 300mm thick wall)
  • solid mass construction giving excellent thermal envolope
  • hygroscopic thereby buffering fluctuating temperature and humidity
  • low carbon footprint (~100kg of CO2 lockup per cubic metre used)
  • fully recyclable and reusable