Hempcrete – Australian Hemp Masonry
Hempcrete is a general term for hemp lime building materials. Also known as Hemp Masonry, Hemcrete or Hemp lime construction it is gaining recognition as a highly energy-efficient, carbon neutral form of building and increasingly being used in the construction of residential and commercial buildings globally, including in Australia.
AHMC Hemp Masonry is a highly sustainable, low-embodied energy product with exceptional thermal performance. It is also termite, pest, mould and fire resistant and fully recyclable and reusable.
Early hemp lime building research projects in the UK suggested that hemp lime masonry was 10% more expensive to build with than conventional masonry, however a standard 3 bedroom home built 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.
Our experience in Australia is that simple hemp homes equivalent in cost to brick veneer can be built on easily accessible building sites. The cost of any hemp build is influenced by multiple variables including the site and ease of construction, the hemp finishes chosen (off-form or rendered), fixtures, inclusions, flooring materials and other finishes in the build.
AHMC materials can be installed by builders or owner builders who have undertaken a weekend workshop. This option achieves significant cost savings and is proving to be a great option for lower income home owners.
Commercial Hemp Construction in Australia
The first commercial hemp building in Australia, the new Maths and Science Building at the Cape Byron Steiner School in NNSW, built using AHMC materials is nearing completion. While not of the scale of commercial buildings in the UK, this a major milestone.
UK Commercial Construction projects which serve as great examples of the potential include:
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.
Compared to building with conventional masonry, 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.
The Triangle Housing Project (2011) in Swindon
( 16 two-bed houses, 13 three-bed houses, 7 four-bed houses, 4 one-bed apartments and 2 two-bed apartments.) These buildings were assessed over a 2 year occupancy period through the UK’s Renewable House Monitoring Program. The report (2015), showed thatthe 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”.
The following conclusions were also 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:
“ 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.”
*** While lime production does have a significant energy footprint, the fact that the building material contains such a high proportion of hemp means that this is more than offset.