Glazed building wall as a solar thermal collector

A good chance to separate thermal and living functions of the building shell appears in indirect passive systems, where absorption and accumulation of the transmitted solar energy takes place close to the wall glazing. A wall of this kind, that transmits, absorbs and accumulates solar energy becomes for a building solar thermal collector. In the whole building scale heating demand reduction, due to this passive solar system may reach 14%. Some further reduction of heating but also cooling demand will be possible when internal air exchange between distinguished thermal zones is considered. Total amount of the useful solar gains from well designed indirect system (windows) is very close to the gains attainable form large indirect system (collecting and accumulating wall). But a major advantage of the indirect system consists in significantly reduced overheating risk in winter and summer. Unfortunately, comparison of the direct solar system and collecting wall, based on combined energy use and investment costs criterion, indicates application of rationally designed passive direct systems.