WHAT IS R VALUE?
The R-value is a measure of a material’s resistance to heat transfer. The higher the R-value the higher the level of insulation. The BCA sets out minimum requirements for the R-values of materials used in the construction of buildings.
See http://www.yourhome.gov.au/passive-design/insulation for more information.
R VALUES OF HEMP LIME CONSTRUCTION
UK Energy efficiency, thermal performance and carbon analysis
“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. The lower energy demand in-use, combined with the negative embodied carbon footprint (carbon sequestration potential) of the hemcrete structure at -4.3 tonnes CO2 (compared with +10.7 tonnes CO2 for brick- block house of same dimensions) “
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 with the findings below which were presented at the 1st International Conference on Zero Carbon Buildings Today and in the Future, Birmingham City University, 11-12 September 2014.
Thermal value (R value) achieved in hemp lime buildings
|Thickness in mm of Hemp lime Walling Materials||100mm||150mm||200mm||250mm||300mm||400mm|
|Thickness in mm of Hemp lime Roofing & Subfloor Insulation||100mm||150mm||200mm||250mm||300mm|
WHAT IS THE RECOMMENDED R VALUE IN YOUR REGION?
INSULATION AND RECOMMENDED R VALUES FOR COMPLIANCE WITH BCA REQUIREMENTS FOR AUSTRALIAN CLIMATE ZONES
There are a number of reasons why buildings built with a Hemp-lime composite can perform significantly better thermally than conventional construction:
As well as insulating effectively, hemp-lime materials can absorb moisture and they allow water vapour to move through the building fabric. This makes them very effective in mitigating humidity in buildings.
A number of studies report on the thermal mass aspects of hemp-lime construction and notably its good thermal storage capacity. This dampens diurnal temperature variation and improves indoor temperature stability, (Bevan R & Woolley 2008),(Evrard et al., 2006).
A full understanding of thermal performance in buildings will rely on further scientific research which is underway. This scientific work involves a different approach to building science that will take account of thermal resistance, thermal capacity and mass, heat emissions from materials, moisture absorption and diffusion and other factors.
Using hemp lime for your home will help to:
- keep the warmth inside your home in winter
- prevent heat from entering your home in summer
- reduce your need for heating and cooling appliances
- reduce your heating and cooling related costs and greenhouse gas emissions.
|Typical heat gain in summer for an uninsulated|
home (Source: yourhome.gov.au)