The Australian Hemp Masonry Company

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Thermal Performance

Thermal Performance of Hemp Lime composites

Hemp lime construction offers a range of solutions to building construction, but of greatest interest to anyone choosing to specify this material is its thermal performance. Currently in Australia the insulation or R value is the major measure of thermal performance.  However 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 a number of further scientific experiments which are 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.
Diagram showing typical heat gain in summer for an uninsulated home. Ceiling 25-35%, Walls 15-25%, Floor 10-20%, Air leaks 5-15%, Windows 25-35%.
Typical heat gain in summer for an uninsulated
home (Source: yourhome.gov.au)
Diagram showing typical heat loss in winter from an uninsulated home. Ceiling 25-35%, Walls 10-20%, Floor 10-20%, Air leaks 15-25%, Windows 11-20%.
Typical heat loss in winter from an uninsulated
home (Source: yourhome.gov.au)

What is an insulation R-value?

The insulation 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

What is the recommended R-value in your region?

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BCA – Min R-Values

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Thermal performance and hemp – lime construction

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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 (compares with +10.7 tonnes CO2 for a brick- block house of same dimensions)”

Proceedings of the 1st International Conference on Zero Carbon Buildings Today and in the Future, Birmingham City University, 11-12 September 2014.