The light transmittance of PC systems is lower than the corresponding glazing system solutions, above all for types S5 and S9 (the reduction is about 30–35%), even if the light is diffused, avoiding glare problems and improving visual comfort in some situations. In general, the measured light transmission values of PC systems are adequate for non-residential buildings, because in these buildings the transparent areas are usually large and they often cover the whole fac¸ ade