Cooling roofs through low temperature solar-heat transformations in hydrophilic porous materials

The principle of roofs cooling through the water vapor adsorption–desorption cycle in porous materials is presented. In order to study the effect, porous materials of natural origin or synthesized at our laboratory were characterized at the micro-scale with UV–VIS-NIR spectrometry, thermal and water vapor adsorption measurements and tested at the urban scale in a wind tunnel of controlled environmental conditions and simulated sun. In the later, the difference of temperature increase under simulated solar irradiation between a highly hydrophilic mesoporous sample and marble dust with comparable reflectance indicates that the low temperature solar heat transformation and evaporation cooling can be considered as an additional mechanism toward the reduction of building heat fluxes.