The paper presents results of simulation tests for the heat balance of double, triple and quadruple glazed windows with eastern, southern, western and northern exposure, conducted for the climate conditions of the city of Poznań and the Wielkopolska region in response to the needs of eco power engineering. It was shown that in the summer period a greater number of window panes and a change in exposure from southern to eastern, western and northern result in a considerable reduction of heat balance for these windows. In the summer months from May to August heat balance of windows with eastern, southern and western exposure is comparable. The heat balance of windows with the northern exposure is much lower in each month of the summer period. In the winter period the highest and positive heat balance is recorded for windows with the southern exposure. Windows facing the other geographical directions have a comparable balance with values around zero. At all the exposures an increased number of window panes to a relatively limited extent improves heat balance, in general for the entire winter period and in its individual months.