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Water tightness in an aluminium window.

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How is water tightness determined in an aluminium window?


In other articles we talked about the importance of air leaks and how Class permeability was calculated; now we are going to talk about the subject of water tightness in aluminium windows. Windows are designed to provide natural light, while they protect us from weather elements such as temperature, wind, rain, etc. Therefore, one of the factors to consider when prescribing an aluminium window it is the water tightness level of the window. But… How do we know if an aluminium window is really watertight?

Windows must undergo strict quality controls in order to prove its resistance, insulation and water tightness capabilities. In the case of water tightness, the tests are carried out in accordance with de UNE-EN-1027 standard. Water tightness in a window is its capacity to avoid water filtrations. The classification according the water tightness is measured by the pressure level where the first filtration occurs. This scale uses an alphanumeric index and it is divided into segments going from less tightness to more tightness, from 1A to 9A. CTE doesn’t require minimum water tightness in windows in its Basic Document of Protection against Dampness. However, in Extrual we take very seriously water tightness performances in our aluminium windows.

Test Procedure

To calculate the classification of each window, they are sprayed with a certain amount of water, through many nozzles, on their outer surface while high pressures are applied till the water flows to the inner surface. In the test the windows are exposed to the specific conditions of a hurricane, withstanding 160 km/h winds and being sprayed with more than 450 litres/hour of water

There are two test methods. For method A the nozzles have a 24º angle direction below the horizontal towards the window. While in method B the windows are sprayed in an 84º angle. The amount of water also varies depending on the method; 21/min.m2 for A and 11/min.m2 for method B. Once the sample is conditioned, the test is carried out in the following manner.

  1. First the sample is sprayed just with water for 15 minutes.
  2. Then, every 5 minutes, pressure is increased in 50 Pa steps until it reaches 300 Pa. Once there the steps increase by 150 Pa reaching 600 Pa after one hour of test.

 The results record the pressure and the place at which the water infiltration occurred, and the time that passed in that pressure till penetration.



If you are looking for aluminium windows with high tightness, you can trust us. Our E-65 series has a E-1200 Pa tightness and a thermal transmittance of 1,2 W/m2K. With any doubt we are talking about one of the best opening windows in the market.

Useful links

Opening window E-65 Series (here)


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