The amount of heat that buildings lose from Windows in winter is considerable. According to U.S. statistics, about 30 percent of the energy consumed by buildings is lost through Windows. In Sweden the proportion is even higher, at about 70 per cent. China's statistics show that about . The practice at home and abroad has proved that improving the thermal insulation performance of building envelope, especially the thermal insulation performance of Windows, is an economical and effective method to prevent the heat loss of buildings. The application of insulating glass in architecture plays a key role. According to us data, the annual heating energy consumption of silver grey hollow glass Windows in high-rise office buildings is 5494KJ per square foot, which is about 2/3 less than that of single glass Windows (17775KJ per square foot).
With the development of China's national economy, the state has increasingly high requirements on environmental protection, energy conservation and improvement of living conditions, and a number of technical regulations have been formulated accordingly. Revised in 1995 "civil building energy-saving design standards" < JGJ26095 > (hereinafter referred to as the new standards) required that the building heating energy consumption is lower than the standard in the 1980s (the building bears 30%, the heating system bears 20%), the building enclosure structural materials and Windows heat transfer coefficient put forward new requirements.
The heat transfer coefficient of single glazed glass window is 6W/ m2.k, the heat transfer coefficient of single framed double glass steel-plastic composite window is 3.5w/m2.k, and the heat transfer coefficient of single framed double glass plastic window is 2.6w/m2.k. Insulating glass must be used for Windows with a heat transfer coefficient below 2.5w/m2.k.
According to the new standards, Beijing, tianjin, shenyang, dalian and other places to adopt double glass can meet the requirements. But double glass is easy to produce condensation problem, especially when double glass seal is not strict, the inner surface of hollow glass is easy to fog and affect the performance. Therefore, replacing double glass window with insulating glass is an inevitable development trend.
Although the new standard of our country is opposite the requirement of coefficient of heat transfer of window had very big raise than original standard, but there is certain gap still compared with abroad.
At present, the main problem of using insulating glass in China's construction industry is the increase of building cost. The increase in building costs can be quickly recouped from the savings. The results of technical and economic calculation of buildings using insulating glass made by the planning department show that the energy-saving effect obtained by using insulating glass in cold areas of China (northeast China and Inner Mongolia) can compensate the increased building cost within 4-5 years.