Air Flow WindowAn Effective Element in Reduction of Buildings' Energy Consumption in Tehran

In the past few decades, at the time of the beginning of energy crisis in the World, efforts to reduce energy consumption in buildings has led to vast and serious skin insulation in both old and new buildings. Insulation to avoid heat transfer and cold air infiltration, along with supplying fresh air and maintaining indoor air quality has challenged experts in the building industry all over the world. When this challenge gets together with the tendency to use more glass surfaces in buildings, a new kind of window is invented to fairly overcome troubles in a novel way. This new window, named “supply air window”, is one of the four kinds of “air flow windows”. In a supply air window there are three layers of glass, a conventional double glazed sealed unit and a third sheet of glass. The air gap between the double glazed unit and the third sheet is not sealed. There is a vent hole to the outdoors at the bottom and another vent leading to the indoors at the top. Fresh air comes in from the bottom and moves up between the panes of glass before entering the room. As it rises, the air collects heat from the indoor pane of glass and carries it up into the room instead of allowing the heat to escape outside. Furthermore, heat from sun, trapped between the glass layers (greenhouse effect), is also collected and carried into the house. You get fresh air coming into the room but it is not such cold air, having recycled energy which would otherwise have escaped, and picked up more from the sunshine. The effective U-value is dramatically decreased. The purpose of this article is introducing the supply air window and implementing feasibility study about its endemic use. To achieve this goal, structural investigation of the window has been done using computer simulation-with WIS program- and numerical calculation -according to ISO standards- to find the best structure with the optimum performance for heating period in Tehran. Results of the investigations on 5 different configuration showed that having one Low-E coating on the third layer of the window (with other characteristics mentioned in the paper), leads to the best temperature and comfort conditions and eventually with the lowest energy consumption, it can have the best performance. Also, the influence of parameters such as air velocity, depth of the ventilated space and windows geometry on the performance of the window, were studied. After that, the impact of the window on the building was examined through its use in a given room and comparing the results of obtained consumption load with the room with conventional windows.  The results indicates higher ability of the new window to increase the performance of glass surfaces (reducing heat transfer and improving thermal comfort) and also reduction in energy consumption in the ventilation part, so that utilizing supply air window leads to 46% final energy saving compared to triple pane window and 50% reduction in energy consumption compared to ordinary double pane windows