At present understading the behaviour of buildings with respect to energy useage becomes a difficult task due to the various factors affecting the energy use. Neverthless, the perpetual advent of software have provided plenty of oppetunities in forecating energy performance of a building,once it is put for usage. In the present study an energy simulating tool is used to model the thermal, ventilation and various energy intaking processes in a building to forecast its energy performance. In order precisely calculate the energy usages in building the tool consider the outside claimate of the building warmth resources within the building and the use of construction materials. This building energy imitating technique is argubly proved as an influential practice for observing energy routine of building,estimating architectural design, decide upon appropiate structural resources and system required as well.Using this tool complex issues with respect to buildings could be scrutinized and their performances also be appraised.