Annual thermal performance of ventilated roofs in different climates: an energy analysis

According to the increasing desire and necessity to use all the available indoor spaces, the attics are more and more used as living spaces in buildings. In regions with high level of solar radiation such as Mediterranean countries, the roofs receive large amounts of solar radiation during the summer, and their superficial temperature can reach values between 60 and 70 °C causing unacceptable indoor conditions. As a matter of fact, ventilated roofs have gained more and more interest in recent years due to the possibility to reduce the cooling load and the energy needs of buildings. The paper reports on the effect of ventilated roofs, comparing the annual energy performances of a typical residential building with a ventilated roof with one with a traditional no-ventilated roof. The simulations are carried out by Trnsys coupled to Comis, a multi-zone air infiltration, ventilation and contaminant transport simulation program. The two software are used in a parallel operation strategy to simulate the ventilated roof building in different climates, in order to analyze the energy effectiveness of the different solutions varying the slope of the roof, the thickness of the air layer, the orientation and the thermal insulation level of the building. The results are discussed in terms of cooling and heating energy needs of the reference building.