The adaptation of building constructions to energy saving requirements entails the study of the performance of constructive systems making up the building envelope. Since the facade is the envelope constructive system of greater impact, in terms of energy demand, the thermal characterisation of its components is of great interest. In this article, hardened lime pastes and different lime mortars with dolomite aggregate and calcined diatom additions at different temperatures are compared, firstly, in terms of thermal conductivity. Parameters such as aggregate type, binder, aggregate proportion, water content, bulk density of the mixture in hardened state and compaction time are studied as well. The wide application of lime and diatom mortars, in relation to traditional lime and mortars containing crushed marble, with reductions of their thermal conductivity up to 41.5% is proven, from the results of this research. (c) 2014 Elsevier B.V. All rights reserved.