The effect of glazing on nZEB performance

In the last decades, European countries have provided for stringent energy requirements for new buildings. In improving the energy performance of buildings, windows play a significant role as they largely influence the energy need. The windows design should base on the balanced trade-off between the solar heat gains and the heat transfer by transmission. In the paper, for some Italian climatic zones, the relation between the optimal window-to-wall ratio (WWR) and the energy need in residential nearly zero-energy buildings (nZEBs) is investigated. In the case studies, the envelope thermo-physical properties are consistent with the nZEB requirements established at national level. The energy performance assessment is carried out by means of a detailed dynamic simulation tool (EnergyPlus). The influence of different orientations and sizes of windows on the energy performance and the peak power are studied. The paper analyses the effect of WWR in the design of nZEBs.