The process of olive oil extraction produces olive stone, a residue which cause considerable problems of disposal. This paper proposes and analyzes an original use of olive stone in order to improve the heat insulation performances of cement lime mortar and reduce its final density. To this purpose, the paper illustrates a set of small-scale tests, which were conducted on specimens of cement lime mortar mixed with different percentages of olive stone, in compliance with the protocols ISO. These tests allowed to evaluate the relations between thermal conductance, density and water absorption per each percentage of olive stone. It was observed that adding 70% of dry weight of olive stone allowed to reduce the average thermal conductance of cement lime mortar by over 76% and its density by around 30%. Furthermore, tests highlighted that the decrease in thermal conductance, which was related to the increase in the percentage of added olive stone, is greater than the decrease in density. In order for the tests to be carried out, a prototype of portable measuring system was developed, which was based on the measurement of heat flow and allowed to obtain average thermal conductance values with average error below 10%. (C) 2013 Elsevier B.V. All rights reserved.