Air Tightness Research Of Building Windows In North China Cold Area

Building energy consumption is taking a huge proportion of total energy consumption.And the energy consumed by building HVAC system is 56%to 58%of building energy consumption.For a building,the energy consumption is consisting of two aspects of heat loss,the heat quantity consumed by heat conduction of building envelope and heat quantity used to heat the infiltration outdoor air.Air infiltration is influenced by building airtightness and the pressure difference between indoor and outdoor air.As to the building in China,the airtightness of building windows is the primary factor especially in North area with a temperature difference larger than 20 ~oC.In order to precisely analysis the energy consumed by cold air infiltration,we need to have a visualized understand of the airtightness of building windows.The windows frame material and switch form have experienced a large innovation in the past several decades as with the development of economy and manufacturing ability in China.According to the results of other researchers,we summarized the windows form used in different decades in North area of China.And we picked out Tianjin as typical area because of this place contains buildings of different years.Based on relevant statistics data,we get the residence building area of every year.By field research,we concluded the most common used windows in Tianjin area.At last,we decided to get the infiltration data of these windows by experiment measurement.After comparison and selection,we finally choose five types of windows as measure object.They are PVC monolayer windows,PVC double layer windows,aluminium alloy sash windows,aluminium alloy casement windows and aluminium alloy inclined sash windows.We totally measured 15 windows for every type contains 3windows.And we also compared the influence of window frame type and switch form on the performance of air tightness.Except for aluminium alloy inclined sash windows,the other 4 kind windows nearly have the same air tightness performance.When the pressure difference between indoor and outdoor air is 5 Pa,the infiltration rate is among 10 and 20 m~3/h.For these 4 kind windows,with the pressure difference variation from 0 to 60 Pa,the air infiltration rate range from 10 to 60 m~3/h.According to testing results,the aluminium alloy inclined sash windows have the largest infiltration rate.For different windows,air tightness performance is rated to the switch form,frame material,using time and function environment.In all of these windows,the aluminium alloy inclined sash windows have the worst air tightness performance,and PVC double layer windows is the best.However,the PVC material will age and deformation during function period;this will affect its air tightness performance.Because of illumination,the windows in lower layers with less infiltration rate than higher layers.Even though traditional pressurization method can measure air infiltration rate accurately,with many preparation need to do before testing,this method is troublesome to operate.At last,we proposed a new method to measure the penetration rate of windows.This method is based on infrared thermal imaging technical.By an IR camera,we can get the temperature distribution on the window surface.According to these information and indoor/outdoor pressure difference,based on heat transfer theory and energy conservation law,we can calculate this penetration rate.This newly proposed method can not only measure the infiltration rate but also get the crack size.By means of experiment,we verified the veracity of this method.For the results of laboratory testing,the error is less than 30%and most of the results are less than 15%.The crack Height measured by IR method is 25%-50%bigger than real crack,closed to real Height.So we consider this method is a reliably method to test window air penetration rate.