Currently heating and cooling account for 36% of Australia’s household energy consumption and shelter accounts for 29% our overall footprint per capita. Thermally efficient housing that is sourced from renewable resources offers a solution to this situation.
Zero Energy Building
A recent two year monitoring program on renewable houses in the UK found that the “insulating properties of hemcrete mean that heating plant can be reduced in size, reducing corresponding energy consumption and carbon emissions, which 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 hemcrete construction.”
Proceedings of the 1st International Conference on Zero Carbon Buildings Today and in the Future, Birmingham City University, 11-12 September 2014.
In early comparative analysis of identical brick and hemp homes in the UK, in the hemp home a desired temperature of 21º C is reached after the heating has been on for around 2 hours, and is then thermostatically maintained at that level for the remainder of the heating period.
In the brick house, however, a maximum temperature of 20º C is only reached after the heating has been on for approximately 4 hours. Therefore, in the morning, when the heating is on for a shorter period of time, the desired temperature is never reached in the brick house. (Centre for Alternative Technology, Wales)
When Hemp Masonry it is exposed to the sun it warms up very little, and when the outside temperature drops it is able to release heat to balance the difference in temperature between the inside and outside. (Perier 2001) These properties were also confirmed by the BRE’ s tests (2001) in Haverhill.
To date governments have focused predominantly on programs to reduce energy usage and while these are certainly necessary, so far there has been little concern about the methods and materials we are using to achieve these reductions.
Fossil fuel based insulation products requiring a lot of energy to manufacture are commonly recommended but this does not make a lot of sense if the goal is to reduce greenhouse gas emissions.
Hemp lime construction offers the opportunity to achieve high levels of operational energy efficiency and avoid energy costs as well as creating a building fabric that has a low embodied energy because it is primarily based on an agricultural commodity and does not require kiln baking to cure, instead drawing in carbon from atmosphere and locking that into the structure.
An outstanding example is the construction of the Adnam’s Brewery and Distribution Centre in Suffolk, UK (2006) where the environmentally sound choice to build the 4400 sq m building with 500mm thick hemp walls raised the cost of the 5. 8 million pound project, by 40,000 pounds, however this allowed the client to avoid installing a 40,000 pound cooling system and to avoid the ongoing costs of running the cooling system. The warehouse maintains a 12º – 14ºC environment.
More than 500 tonnes of CO2 emissions were saved compared with using conventional materials.
“Having a low impact, carbon-negative, sustainable form of construction that can be used in volume house building or even multi-storey office blocks, factories and warehouses is an exciting development that provides a genuine solution to demands for zero-carbon construction.” (Rachel Bevan & Prof. Tom Woolley, Hemp lime Construction, A Guide to Building with Hemp Lime Composites, BRE Press, UK)