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

The principle of roofs cooling through the water vapour adsorption-desorption cycle in porous materials is presented. In order to study the effect, porous materials of natural origin or synthesized at our lab, were characterized at the micro-scale with SEM, XRD, UV-VIS-NIR spectrometry, thermal and water-vapour 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 (300 W/m2) between a highly hydrophilic mesoporous sample and marble dust with comparable reflectance was almost 5 C in the first irradiation hours and reduced to 2 C at the end of irradiation.