Following a successful inter-comparison of methods to measure the thermal conductivity of thin specimens of masonry materials, a second inter-comparison involving seven participants of the first investigation has now been carried out on a specimen of low density insulating autoclaved aerated concrete. Base values were determined by three established organizations using the guarded hot plate method. Three organizations then used the guarded heat flow meter and three used contact transient methods. Details of the participants, the material, the apparatus features and test criteria are provided together with a summary and discussion of the results. Overall, the results are promising with very good agreement deviations (<3% to 5%) obtained between the hot plate and guarded heat-flow meter methods providing that the specimen thermal conductance for the latter method was within the original calibration limits. However, there is somewhat less agreement (deviations <10%) between the results of the transient methods and the hot-plates. Possible explanations are discussed and should be investigated further. It would appear that while the steady-state method is suitable for the overall thermal conductivity range of appropriate masonry materials, the use of transient techniques is questionable for the low density cellular forms of material.
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