The southern curtain wall composed of PV modules is capable not only of electricity, but also heat generation. The sun rays falling on their surface are being
transformed into the heat. Due to the so-called "greenhouse effect” the heat is trapped in the empty space between the layers. In this way, a 15 cm cavity is heated by means of insolation. During winter, the heated air is conducted to a heating plant, where it is used to warm the fresh-air intake. The heat gains from PV modules surface also play a significant role in passive heating and cooling of the inner space. The cavity becomes a passive solar collector and thermal buffer. It participates in decreasing unfavourable temperature fluctuations by the inner layer of the southern wall, as well as constitutes an extra thermal isolation. The same thinking happens in summer. The heat coming from the PV modules causes the so-called "stuck effect” that intensifies natural ventilation in the void between two layers. This enables to draw out used warm air from the inner space, favourably increasing air volume exchange. This contributes to preventing overheating during sunny outcast days. In this way, the PV modules’ usage exerts influence on thermal comfort directly all year round (fig.2).

In terms of visual comfort, the cells within the PV modules are laid to a pattern that allows daylight to pass through the gaps. This creates a pleasant lighting environment in summer, shielding the interior against excessive direct sunlight and giving subdued natural light under heavy solar radiation. On the other hand, the densely laid opaque PV cells stop desirable winter daylight causing the inner space to be naturally lit with the aid of the skylights, glazed surfaces in the rear walls and glazed „belt” in the upper part of the southern curtain wall. During outcast days, sun rays leaking through the gaps cause strong contrasts and shadow patterns on floor surfaces that may disadvantageously affect lighting environment and comfort of the user.

fig.3lighting environmentbythe Last but not least the curtain waN made of PV

wall with PVm0dules modules does not allow the occupants to retain visual

contact with the outside (fig.3).