The presence of water inside the walls can be considered one of the most important causes of degradation in historical buildings. In particular, evaporation can give rise to salt deposits inside the superficial pores. Evaporation flux from wall surfaces can quantitatively be estimated by measuring the surface temperature since it depends in a sensitive way on the evaporation rate. The value of the surface temperature, in equilibrium conditions for all the different heat exchange contributions to the wall, depends on the evaporation rate, material's thermal conductivity as well as temperature and ventilation experimental conditions.Several experiments have been performed on brick, plaster and stone specimens with different porosity values in the laboratory of the "Istituto di Fisica Generale Applicata" to empirically obtain correlations of temperature with evaporation rate. A climatic room with controlled environmental parameters (temperature, relative humidity, ventilation, thermal irradiation) was employed and cooling effects due to evaporation were investigated in steady conditions by a SW IR thermographic camera.Tables for evaporation rate, water content and surface temperature values (Φ, Wc, Ts) were obtained for several materials. Applicability limits of the thermographic technique for moisture detection are discussed.