Why do double glazed sealed units fail?
Not sealed correctly during manufacture: If a sealed unit is not fully sealed all the way round, or not sealed properly, the unit is likely to fail within a relatively short time scale, and this will be normally within a year. This would be covered under the manufacturer’s warranty period (five or ten years). Not seated correctly on glazing blocks: Difficult to be exact about to what extent this will contribute to premature failure, as each case will vary. Worst case would be if drainage was blocked together with even a small amount water getting in, which could reduce the life of a ‘good’ unit by around 50% in terms of its otherwise fair life expectancy. Exterior seals not fitting correctly, letting water in: Again, similar to above, but if some of the water getting in contains washing up liquid or similar, then this will attack and degrade the perimeter seal, usually along the bottom edge. Anything stuck together will come apart quicker if immersed in water, and even quicker if that
