Most curtain walling manufacturers stand back from making roof glazing. Why? Because it is difficult! The combination of rain and wind leads to water defying gravity and running uphill and not just downhill. Therefore, normal principles for water tightness do not apply.It is not possible to design a roof light which will prevent water from entering under all thinkable weather conditions. This is particularly true if part of the roof light is openable. Any high quality roof light must effectively drain penetrating water before it enters the actual building. An energy efficient roof light has to be airtight. In windy conditions there are large pressure differences between the different sides of the building – not least on the roof! This requires a solution with double sealing layers.Efficient air tightness measures will also prevent warm moist air from inside the building entering the roof light construction and condensate on the colder outer surfaces. Vitral has developed and produced roof glazing solutions since 1956 and has substantial experience in making water and airtight solutions free of condensation risks Vitral’s solutions are tested for water and air tightness. Always demand from your roof glazing supplier that the product is tested by an accredited and independent test institute and meets relevant regulations..