The insulation of the building envelope contributes to the reduction of annual energy consumptions. The development of new materials, such as fibre reinforced insulating coatings, could be useful in order to obtain an effective solution for the improvement of energy performance and for reinforcement of the walls. The evaluation of the thermal and mechanical characteristics of building coatings with good thermal insulation properties and mechanical resistance is the aim of the present paper. A new experimental apparatus, Small Hot-Box, built at the University of Perugia, was used for the evaluation of the thermal conductivity of four different coatings (with and without a reinforced structure). No European standards are available for this innovative facility, but it takes into account some prescriptions of EN ISO 8990. The apparatus was calibrated with materials of known thermal conductivity. The thermal conductivity can be calculated with both the thermal flux meter and the Hot Box method. Good values of the thermal conductivity, in the range of 0.09–0.11 W/mK were found for all the samples, except for one (0.21–0.24 W/mK). Mechanical tests were also carried out in laboratory on all the samples and results were used to evaluate the shear modulus and strength of the wall panels.