In order to get a realistic analysis of the optical performance of the Photovoltaic modules, a room has been considered where a traditional glass fagade was replaced by a PV fagade made of high visual modules. In that case the solar light was measured before and after the application.

The intervention aimed to increase the comfort in order to increase the control of the direct light entering the windows and to avoid the over heating, particularly in the summertime.

The day light factor method [4,5] has been used to characterise the indoor lighting conditions.

The daylight factor DF is defined as the ratio of the solar lighting in a particular point inside the room E divided for the lighting outside on an horizontal surface facing the hemispherical sky without any obstruction.

A method to have an approximated value of DF is the average day ligh factor DFm defined as

DFm = Eim / Ee, hm x 100

Ei is the average solar lighting on a point inside the room [lux]

Ee, hm is the average lighting on an horizontal plane outside, caused by the whole sky, excluding the direct component [lux]

The room is a part of the CR ENEA building at Portici (Na). It is located at the ground floor,

3.6 mx5 m, for a surface of 18 m2. The fagade facing the South presented a surface of

11. 7 m2 completely glazed and it is the object of the project.

Initially the fagade, 5.01 x2.14 squares meters, in a structure made of reinforced concrete, was divided in four vertical windows, divided with frames. The project intended to keep the original dimensions but has been realized in a different way, with three vertical partitions including two modules each. In conclusion the PV fagade is composed by 6 glass-glass modules realized by Schuco using the SGgPROSOL® technology in a sandwich structure with the two external panes made of heat-strengthened glass (sGGPLANIDUR®) and the solar cells bonded between them by means of an high-transparent resin.