Solar reflecting tile coverings for traditional South-European Buildings

An effective solution to summer overheating of buildings is provided by “cool roofs”. These are building coverings with high reflectance to solar radiation and high emittance in the infrared range. They have been investigated extensively in the U.S.A., where certification procedures have already been developed by independent bodies, and certified products are commercially available.Common cool roof products have white or very light colors. As a result, they are difficult to use in most ancient or traditional south-European buildings, which typically have steep-slope roofs covered by red clay tiles. On the other hand, in places like the historical centers of Italian and other Mediterranean cities the rooms immediately below the roof are often inhabited, so that the relatively low solar reflectance of tile coverings makes summer overheating a major problem. This can be effectively addressed by using tiles coated with “cool colors”, that is colors with the same spectral response of clay tiles in the visible, but highly reflecting in the near infrared range, which includes about half of solar radiation. Cool colors can yield the same visible aspect of common building surfaces, but much higher solar reflectance.In the aim of verifying the potential of cool color tile coverings, an investigation was started at the DIMeC. Materials for cool color coating were analyzed in the laboratory, verifying their radiation properties as a function of composition and pigment content. Prototypes of red roof tiles have been built using easily available materials with solar reflectance almost twice that of conventional tiles.