Energy savings and summer thermal comfort for retrofitted buildings: A complex balance

In the last years many buildings in Europe have undergone energy retrofit, in order to improve their performance and reduce the energy needs. In most cases, retrofit solutions were based on the application of insulating materials either to the outside walls or to the roof. Such a practice, which undoubtedly improves the winter performance, can also induce non-negligible drawbacks in summer and in other warm months, mostly due to solar gains. The aim of this paper is to study the consequences of a typical retrofit solution, aiming to get the “nZEB” label, on summer thermal comfort. The study is based on dynamic simulations carried out with EnergyPlus on a public residential building, located in the city of Catania, Southern Italy. The analysis is repeated for various values of the insulation thickness, to be applied to the outer face of the external walls. Besides, nighttime ventilation is scheduled in summer at various opening rates of the windows, with the aim to reduce overheating. The results of the simulations may help designers to find the right balance between insulation needs and summer thermal comfort for the retrofit of existing residential buildings.