Weather Performance Testing and Ratings Explained

Weather performance testing assesses if windows and doors meet the requirements set out by British or European Standards.

Glazing systems can be tested to prove their effectiveness as a barrier against weather including water tightness, air permeability and wind resistance. The windows and doors are then given a ‘class’ to indicate how they performed in each test.

The BS 6375 series of standards includes testing pressure levels for air permeability, watertightness and wind resistance for external windows and doors.

sieger glazing package including slim sliding glass doors and casement windows

Air Permeability

It is EN 12207 that tests windows and doors for air permeability. This is designed to test the amount of air that will travel through a glass elevation under pressure from elements such as wind.

The test is in accordance with BS EN 1026 and the windows and doors to be tested are done so at a third party, accredited testing facility to ensure accurate ratings.

Negative and positive air pressures are directed at each side of the system once it has been built into a testing unit. This method tries to both force air at the window from one side and suck air through the window from the ‘internal’ side.

The resulting classes denote how much pressure the window or door was subjected to with acceptable air travel through the system. Windows and doors tested to Class 4 indicate a product that was tested with air pressures of 600 Pa in pressure.

It is also a requirement of the Building Regulations in all regions of the UK that new homes are assessed for overall air leakage.

steel look sliding glass doors with glazing bars and gable end windows and rooflights
three pane black bifold door with tall fixed casement windows

Water Tightness

Windows and doors are tested for their water tightness under EN 12208 and testing is carried out as per BS EN 1027.

The window or door is installed within a testing rig and water is forced at the windows through water nozzles at differing pressures for lengthening periods of time, replicating rain.

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.

The highest designated class is 9A which indicates the glazing system was unprotected and withstood 600 Pa of water pressure for 55 minutes.

Classes 1-7 with a B sub-label indicate that the windows or doors were partially protect by a balustrade or similar.

Wind Load

The resistance to wind load is tested through EN 12210 in accordance with BS EN 12211, it is designed to test the wind load a window or door can withstand without serious deflection or damage.

The resulting classes are broken into two elements; the number (1-5) which indicates the pressure of wind applied to the product and the letter (A-C) which indicates the amount of deflection accepted in the test.

For example, a class 5 tested product has been tested with winds up to 2000 Pa pressure.

The resistance to window load test includes a deflection test, a repeated pressure test and operational test, an air permeability test and finally a safety test. The Air Permeability Test is repeated after the Wind Load Test to assess the damage that may have occurred during this test.

aluminium lantern rooflight above a four pane bifold door with a traffic door
three pane aluminium bifold door bringing light into a pastel coloured kitchen extension
In all of the above tests an ‘E’ results (such as E2400) indicates the tested product exceeded the defined testing method boundaries and testing was continued with increasing pressures. The number following E shows the pressure the window or door was tested to.

If you have any other questions about glazing or Sieger Systems, don’t hesitate to get in touch with our team.

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