Weather Performance of Windows And Doors


Weather performance testing is a means of assessing the product’s ability to achieve specific requirements in areas such as air permeability, water tightness and resistance to wind load . 

Weather testing includes: 

  • Air Permeability
  • Water tightness
  • Resistance to Wind Load

Relavant standards for weather performance

The relavant standards are as follows: 

  • BS6375 Part 1 is the classification for weather tightness and guidance on selection and specification.
  • BS EN 14351-1 is the harmonized European Standard for windows & external doorsets.

ions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).

Air permability test (BS EN 12207)

The air permeability, air leakage or air tightness is the measure of the ability of a window or door to resist the uncontrolled flow of air (in or out). Air permability test measures the volume of air that would pass through a window or door at a certain pressure.

Performance levels are grouped into four ‘classes’ where class 1 is the lowest level of performance and
class 4 the best.

Watertightness test (BS EN 12208)

The objective of the test is to determine the watertightness of the windows and doors by applying a steady water spray test to the product and applying air pressure to the product which is increased every 5 minutes.

Resistance to wind test 

The resistance to wind load test includes a deflection test, a repeated pressure test and operational test, an air permeability test and finally a safety test.  This performance feature guarantees that external windows and doors are wind resistant. Because the resistance to wind load is an important design factor especially in high-rise windows and doors and in exposed facades, where the wind pressures are considerable. 

Relavant standards are as follows: 

  • EN 12210: Windows and doors – Wind resistance – Classification
  • EN 12211: Windows and doors – Wind resistance – Test method

The standards provide for 5 classes (+ specific) with three test pressures for each class:

  • P1: Measuring distortion
  • P2: Repeated 50 times
  • P3: Safety test

Performance for maximum test pressure is grouped into 5 classes, where class one is the lowest performance and class 5 is the best.



0No test

BS EN 12424 distinguishes between 5 wind classes, where class 0 provides no information on the wind load and always applies when no measurement is being carried out.  

Performance levels for deflection are grouped into classes A, B and C, where A is the worst and C is the

A class 5 window or door can withstand 2000Pa of pressure, which is the equivalent to 127mph winds. To put this into perspective, on the Beaufort Scale, when the wind exceeds 74mph it is classed as a force 12, which is hurricane force.