Assessing cooling energy performance of windows for residential buildings in the Mediterranean zone

Heat transfer through windows accounts for a significant proportion of energy used in the building sector for covering both heating and cooling needs, since the optical and the thermal characteristics of conventional fenestration products constitute them more “vulnerable” in energy flows when compared to opaque building elements. In this study, an approach for evaluating the cooling energy performance of residential windows is presented. It is based on a parametric study, which aims at highlighting the impact of the window configuration on its energy behavior in terms of geometrical characteristics, thermophysical and optical properties, as well as orientation and shading levels. The results underlined the magnitude of the relationship between the thermal and optical properties of the transparent elements with respect to their orientation; especially for residential buildings, the solar transmittance determines at a considerable extent the cooling energy performance of fenestration, at least in the warmest part of Europe. Furthermore, the statistical analysis of the derived data provided mathematical expressions, which can be used in praxis for predicting the cooling energy performance of windows with respect to their thermal and optical characteristics.

► Cooling energy performance of residential windows in warm climates is studied.
► It is primarily determined by the window’s solar transmittance g and orientation.
► Advanced windows perform worse when compared to conventional ones with the same g.
► Shading contributes notably in decreasing the cooling loads attributed to the window.
► Equations for predicting the cooling energy performance of windows were developed.