Testing Methods for Determining the Thermal Properties of Earth Building Materials

Jacob Roos - 2003

The inherent variability of earth building materials means there is a lack of reliable information on their thermal properties compared to that for more uniform, mass-produced building fabrics. However, such information is required to assess the thermal performance of a building design. Furthermore, many existing methods for testing thermal properties are unsuitable for earth building materials, as their inhomogeneous nature requires relatively large sample sizes.

The aim of this thesis was to develop and adapt suitable methods for determining the thermal properties of earth building materials and in the process determine the properties of a type of cement stabilised pressed earth. A dynamic, in-situ method of obtaining thermal diffusivity was developed and implemented using a purpose-built instrumented test wall section. Standard laboratory methods were used to obtain other material properties, and the thermal conductivity of the target material at in-use conditions calculated from the combined results.

The instrumented test wall is unveiled to the public at the official 'wall opening' party

The average thermal properties of the target material at equilibrium moisture content were found and were very similar to that for standard ‘sand and gravel’ concrete. The methods developed were successful at obtaining results for the target material within an acceptable error bound, given the significant degree of compositional variation between samples.