Considered facade solar collector is a standard selective liquid flat-plate collector integrated into a building envelope. Layout of investigated type of facade collector is shown in Figure 1. The collector consists of standard spectrally selective absorber (а/є = 0.9/0.09), an air gap and single safety glazing. Collector back and edge insulation is common to building insulation layer. Facade collectors are usually available in wooden frames as large-scale installation panels. Collector panel is directly mounted on insulation envelope of building facade, there is no thermal separation between absorber and insulation envelope in the form of ventilation gap. Solar collector is thermally coupled to the building wall. The integration brings several essential advantages in comparison with solar collectors mounted separately from building envelope (in the front of the envelope or on the flat roof). Additionally to the basic function of solar collector, facade collector serves also as protection shield against atmospheric effects (weather protection) and improves the thermal properties of the building with respect to passive solar gains. Furthermore, collector integration into building

facade is aesthetically more attractive solution when compared to collector plants placed on the flat roofs, which create foreign-like bodies on buildings.