Assessment and improvement of the performance of antisolar surfaces and coatings

Solar reflectance and thermal emittance are key parameters to evaluate solar heat gains through opaquebuilding elements. A high solar reflectance allows building surfaces to minimize absorption of solarenergy, whereas a high thermal emittance allows returning to the environment most of the solar energythat is however absorbed by any actual surface. Therefore, summer overheating of buildings can beprevented by selecting external coatings with proper values of both properties.In this work, the role of radiative properties is explained in quantitative terms. Standard test methodsfor their measurement are also presented. The behavior of some typical cool roof surfaces is then analyzed,in order to point out the limits of qualitative selection criteria and demonstrate the need of quantitativeapproaches to enable product comparison and development. Eventually, the perspectives offered by theuse of advanced materials and coatings are also highlighted.