Two inter-comparisons have been carried out between organisations in the British Isles that undertake measurements of the thermal properties of insulations and other low thermal conductivity materials by appropriate standard methods. The overall aims were to establish that consistent levels of measurement practice were being maintained to declared or acceptable precision limits and to provide information that could be used to assist all organisations to improve their measurement capabilities.The first inter-comparison involved the seven organisations that are accredited by the United Kingdom Accreditation Service for measurements using the guarded hot plate method in accordance with the IS08302. The second included the seventeen organisations that use the heat flow meter apparatus according to IS08301 in research and quality control laboratories particularly those associated with manufacturers of different thermal insulation products.