The air tightness of building doors and windows refers to the ability to prevent air infiltration when external doors and windows are closed normally. Using doors and windows with good air tightness can save heating and cooling energy to the greatest extent. Therefore, controlling the air permeability of building doors and windows has become an effective way to realize energy saving. But the higher the air tightness, the better. At least ensure a certain amount of air exchange, otherwise the indoor air will be turbid, which will affect work efficiency and endanger health.
When testing the air tightness of the external window, firstly, the openable part of the tested part is completely sealed; Then, positive and negative wind loads are applied in stages, and the additional air permeability when the positive and negative loads are reached in each stage is recorded; Then remove the sealing device, repeat the above process and measure the total air permeability.
According to GB/T 7 106-2008 "Classification and Testing Methods for Airtightness, Watertightness and Wind Pressure Resistance of Building Doors and Windows", in the standard state, air permeability per unit slit length q 1 and air permeability per unit area q2 are used as classification evaluation indexes for airtightness.
In order to ensure the accuracy of the grading index value, the measured value under the pressure difference of 100Pa is converted into the corresponding value under the pressure difference of 10Pa, and the average air permeability per unit area of the three specimens is used as the evaluation index to grade their respective grades, and finally the most unfavorable grade of the two is taken as the grade of the group of specimens.
2. Water tightness test
Watertightness refers to the ability of the external window to prevent rainwater infiltration under the simultaneous action of wind and rain when it is normally closed.
When the outdoor wind and rain act at the same time, the rain will penetrate into the room through the gap of the external window, polluting the indoor decoration and furnishings, and causing economic losses and insecurity to the residents.
Rainwater seeps into the window frame profile. If it is not removed in time, the accumulated water in the profile cavity for a long time will corrode metal materials and hardware parts, affect the normal switch, shorten the service life of the external window, and cause the profile to freeze and crack in winter, resulting in serious damage and deformation. Therefore, the geometric shape, size, exposure degree, rainfall, pressure difference between the outer window chamber and the inside and outside all directly affect the watertightness.
Watertightness detection is divided into stable pressurization method and fluctuating pressurization method. It is necessary to choose appropriate detection methods according to different environments in different regions. If it is in tropical storm and typhoon area, wave pressure method should be adopted. The grading inspection and the project are located in non-tropical storm and typhoon areas, and the stable pressurization method can be used. If the fluctuating pressurization method has been used for inspection, the stable pressurization method can no longer be used. The maximum pressure peak value of watertight performance should be less than the pressure difference P3 of wind pressure classification detection. The division of tropical storm and typhoon areas shall be carried out in accordance with GB 50 178.
GB/T 7 106-2008 unifies the comprehensive method of water tightness test values of three specimens: generally, the arithmetic average of the test values of three specimens is taken as the water tightness test value. If the difference between the highest value and the middle value among the three detected values is greater than two detected pressure levels, the highest value is reduced to two detected pressure levels higher than the middle value, and then the arithmetic average is performed. If the smaller two of the three detected values are equal, any one of them can be regarded as an intermediate value.
3. Wind pressure resistance test
The wind pressure resistance of building exterior windows refers to the ability of building exterior windows not to be damaged, hardware loose and difficult to close under the action of wind pressure under the normal closed state, which is evaluated by the relative degree of main stress bars.
The external window is installed on the building. Due to the wind load, the windward side of the building bears positive wind pressure, and the leeward side and side face bear negative wind pressure. At the same time, due to the different internal structure of the building, positive wind pressure and negative wind pressure may also be generated inside, resulting in the combined action of positive and negative pressure on the external window.
As a result of wind pressure, the window strips will be deformed, the splicing gap will become larger, and the air tightness and water tightness will be reduced. When the pressure generated by wind load exceeds its bearing capacity, safety accidents such as permanent deformation, broken glass, hardware damage and even window sash falling off may occur. Therefore, wind resistance is an important index related to safe use. Reasonable selection of stressed members, correct measurement of the length of stressed members and accurate calculation of their maximum surface normal deflection are the core of wind-resistant test of external windows.
The detection of wind pressure resistance of external windows can be divided into three parts: deformation detection, repeated pressurization detection and grading detection. During deformation detection, the surface normal deflection (angular displacement) under the action of each pressure difference is recorded, and the pressure difference corresponding to the maximum surface normal deflection (angular displacement) during deformation detection is obtained by using the relative linear relationship between pressure difference and deformation, which is used as the deformation detection pressure difference P 1.
Repeat the pressure test P2= 1.5P 1, and it should not exceed 3000Pa, and repeat it for 5 times;
Classification detection P3=2.5P 1, which is used to evaluate the level of maintaining the normal use function of building external windows.
GB/T 7 106-2008 unifies the classification of wind pressure resistance of building exterior doors and windows, and adopts the classification detection pressure value P3 as the classification index. The higher the grade, the higher the wind pressure resistance of the doors and windows of the building exterior wall, and the better the wind pressure resistance.