My diploma thesis concentrates on the comparison of the amounts of energy spent for heating and cooling systems in a building with or without glass house extensions. The calculations were made in TOST computer program, developed at the Faculty of Civil and Geodetic Engineering Ljubljana. A glass house extension or a sun-room is one of possible construction elements in bio-climatic architecture. It is mainly used for collecting and storing solar energy and can be easily converted into a comfortable living area. Building a sun-room requires cautious planning as only well engineered glass panels and accumulation materials can contribute to energy savings. The calculations showed that heating energy consumption is lower in house areas within the immediate vicinity of glass house extensions. In distant parts of the building the effect of a sun-room is negligible. Buildings without glass extensions do not require cooling whereas the necessity for cooling systems is greater in all of the affected parts of buildings with sun-room extensions. The cooling energy consumption can be reduced by shading methods executed over sun-rooms as well as on buildings themselves. I have presented two possible methods of shading: using jutting roofs over the glass constructions, and shading with deciduous greenery covers.