Green roof for zero energy buildings: a pilot project

Zero Energy Buildings (ZEBs) and nearly Zero Energy Buildings (nZEBs) can be designed from scratch or they can be obtained after deep refurbishments of existing constructions. Both passive and active strategies are fundamental to achieve the ZEB or nZEB target. According to this, among passive systems, green roofs can be a viable solution because they allow to achieve energy savings, also reducing the urban heat island phenomenon. In this research, an innovative roof-lawn system was preliminary analyzed by installing several measurement instruments for obtaining information about thermal heat exchanges. Heat-flow meters, surface temperature and air temperature probes were installed, comparing the performance of the roof-lawn system with a nearby simple old roof, in order to quantify the two different behaviors from a thermal point of view.

The roof-lawn system revealed its advantages, showing a higher thermal inertia with no overheating and a lower thermal transmittance, as well as better indoor conditions for the occupants of the building. The study is the first step of a path which aims to design a more complex and complete system, also considering the structural part of the roof. (paper)