In Mediterranean regions the solar radiation in summer causes an overheating of the building envelope(roof and walls) and then of the indoor and the need for air-conditioning. Passive systems to limit solar effect mainly consist of ventilated facades and roofs. Roof is the most exposed element to solar radiation and this causes excessive heating of the attic and other rooms, therefore causing a high energy requirement for cooling that is the major energy demand in air-conditioning, not yet regulated by law in several European countries, most of them in South Europe where it should be more important.
130 million of population in South Europe correspond to almost 5.2 billion of square meters of house floor space and from 1 to 2 billion of square meters of roof surface (single or double-storey buildings, mansards and so on). Pitched roofs are very widespread in Mediterranean regions like Italy, Spain and Greece, but also in France, Portugal and so on, thus tiled roofs could be amounted from 50% to 80% of overall roof surface (that means from 500 to 1300 million of square meters). Even if the energy requirement in cooling depends on the age of the buildings and their use, several studies depict in 60 kWht/m2 the energy requirement for space cooling. Therefore, the energy demand for under-roof space cooling range from 30.000 to 70.000 GWht, that are equivalent to 10.000-25.000 GWhe taking into account a coefficient of performance equal to 3 (COP) for the chiller operating.