“…When designing natural ventilation systems, it is necessary to consider factors such as architectural and structural features of orthodox churches [9,10,11], the power of heating systems [12,13,14], heat generation from visitors and inhabitants, candles and church lamps [15]. The thermal and air humidity conditions of ancient time facilities could be the issue of saving the unique interiors and the whole constructions [1,3,5]. And for sure for space heating capacity and heat consumption of historical buildings of different type [4,15].…”