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Basic Knowledge | 2019.12.11
Air tightness, Water tightness and Wind-load Resistance of Building Exterior Doors and Windows
The three physical properties of building fenestration system generally refer to the air tightness, water tightness, and wind-load resistance. These three properties are the required items in fenestration testing.

Air tightness, Water tightness and Wind-load Resistance of Building Exterior Doors and Windows


The three physical properties of building fenestration system generally refer to the air tightness, water tightness, and wind-load resistance. These three properties are the required items in fenestration testing. In 1986, China enacted the inspection standard for the three physical properties of building exterior doors and windows.  The standard was later updated in 2002. The new national standard was revised in the following aspects:

1.  Add the rate of air permeability per unit area as a rating indicator, to derive comprehensive rating when combined with the rate of air permeability per unit seam length rating indicator.  

2.  Add the content of inspecting air permeability rate under negative pressure differential.

3.  Specify the scope of use of the pressure fluctuation on water tightness performance.  

4.  Add the content of engineering inspection over the performance of wind-load resistance.


Air permeability performance, also known as air tightness, refers to the resistance of the closed exterior doors and windows to air leakage. The airtight performance of the exterior doors and windows has a great impact on the heat loss.  The better the airtight performance, the lesser the thermal exchange and the impact on room temperature. The measurement of air tightness takes the air penetration per unit seam length and unit area under standard condition when the pressure difference between the inside and outside the window equals to 10 Pa as the rating indicator. The air tightness is divided into 8 levels. The higher the number, the lesser the heat loss and the better the air tightness. Good air permeability is conducive to energy conservation and environmental protection.


The performance rating of the air tightness of exterior doors and windows

Level

Rating indicator q1

Rating indicator q2

1

4.0≥q1>3.5

12.0≥q2>10.5

2

3.5≥q1>3.0

10.5≥q2>9.0

3

3.0≥q1>2.5

9.0≥q2>7.5

4

2.5≥q1>2.0

9.0≥q2>7.5

5

2.0≥q1>1.5

6.0≥q2>4.5

6

1.5≥q1>1.0

4.5≥q2>3.0

7

1.0≥q1>0.5

3.0≥q2>1.5

8

q1≤0.5

q2≤1.5


Unit of indicator value:

q1: Indicator value per unit open seam. Measuring unit is m3/(m·h);

q2: Indicator value per unit area. Measuring unit is m3/(m2·h)

The data are extracted from “Graduations and Test Methods of Air Permeability Water tightness and Wind Load Resistance Performance for Building External Windows and Doors”.


Water tightness refers to the resistance of the closed exterior doors and windows to water leakage under wind and rain at the same time. General testing of the water tightness of exterior doors and windows is conducted according to the standard set forth in the “Graduations and Test Methods of Air Permeability ,Water tightness and Wind Load Resistance Performance for Building External Windows and Doors”, which specifies in detail the testing equipment requirements, performance testing methods, and the rating  indicators for water tightness. The testing devices simulate the condition of exterior doors and windows in the stormy weather, measure the pressure difference between the two sides of the doors and windows using pressure supply system, water supply system, pressure and water flow measuring system to determine the pressure differential during severe leakage, and finally identify the water tightness factor and rating of the doors and windows. The water tightness of doors and windows is divided into 6 levels with a higher level representing stronger water tightness. The doors and windows with good waterproof performance can effectively prevent the intrusion of rainwater into their internal structure to ensure a longer service life.


The performance rating of the water tightness of exterior doors and windows

Level

Rating indicator(Unit: Pa)

1

100≤△P<150

2

150≤△P<250

3

250≤△P<350

4

350≤△P<500

5

500≤△P<700

6

△P≥700

P is the pressure difference in a severe leakage. As defined in the national fenestration standard, it represents the pressure difference when a severe leakage in the testing samples of the exterior doors and windows occurs.

Severe leakage refers to: continuous spout from the test sample interface; continuous flow out of the test sample interface.  

Level 6 should have the specific testing pressure indicated after rating. The data are extracted from Graduations and Test Methods of Air Permeability Water tightness and Wind Load Resistance Performance for Building External Windows and Doors”. 


Wind-load resistance refers to the resistance of the closed doors and windows to wind pressure without any damages (e.g. cracking, panel breakage, local yield, bonding failure, etc.) and functional impairment such as loose hardware and opening difficulties. There are up to 9 levels of wind resistance for doors and windows. The higher the number, the stronger the wind-load resistance. It is worth noting that the wind-load resistance level is not the same as the typhoon level. Wind load resistance level 9 indicates that the window can withstand more than 5000 Pa of wind pressure, easily resisting the destructive force of the Category 12 hurricane.


The performance rating of the wind-load resistance of exterior doors and windows

Level

Rating indicator(Unit: kPa)

1

1.0≤P<1.5

2

1.5≤P<2.0

3

2.0≤P<2.5

4

2.5≤P<3.0

5

3.0≤P<3.5

6

3.5≤P<4.0

7

4.0≤P<4.5

8

4.5≤P<5.0

9

P≥5.0

The data are extracted from “Graduations and Test Methods of Air Permeability Water tightness and Wind Load Resistance Performance for Building External Windows and Doors”.

Level 9 should have the specific testing pressure indicated after rating.