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

Fenestration has always been regarded as the weak element in the building envelope due to its role in determining of the energy balance of a building. At the same time, cooling performance is becoming a significant parameter for evaluating the energy performance of buildings in Europe. Due to the plethora of window products with advanced properties currently existing on the market, it is not always easy for engineers to select the optimum solution. In this paper, the cooling performance of windows in the warmest part of Europe is evaluated with regard to their geometrical, thermophysical and optical characteristics, as well as their shading provisions. The analysis shows that the contribution of the windows in determining cooling loads is maximized when their solar transmittance is high and their thermal transmittance is low. Moreover, in the Mediterranean regions the increased thermal efficiency of transparent elements in buildings with controlled ventilation, such as offices, prohibits the dissipation of heat toward the ambient environment and ultimately result in higher cooling energy loads.

► The cooling energy performance of windows in Mediterranean zone is evaluated.
► Their geometry, U and g values and shading are taken into account.
► Cooling loads attributed to the window are maximized when g is high and U is low.
► Increased window thermal efficiency prevents heat dissipation and results in increased cooling loads.
► Shading is more efficient when the window's solar and thermal transmittance is high.