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Why have my windows gone misty ?


Window units are made and inserted with desiccant during manufacture. This is used to take the moisture out of the sealed unit. After a number of years or if damaged the desiccant will begin to fail. The result of this is that your windows become filled with condensation.


What is the most common cause of premature failure in windows?


If a unit is not fully sealed all the way round, during manufacture, the unit is likely to fail within a relatively short time scale.The worst case is when the drainage is blocked, with even a small amount of water getting in. This can reduce the life of a good unit by around 50% in terms of its life expectancy.


What happens if the seal on the outside gets broken?


Similar to the 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 that has been stuck together will come apart quicker if immersed in water, and even quicker if that water contains a solvent or any oil based contaminants.


More Q and A from the DIY “NOT” website


I have some window units that have blown and wondered if it's somehow possible to remove the moisture from the inside of a double glazed unit rather than buying new units. This will only be a temporary fix as I plan to fit new windows when funds allow. I thought about drilling 2 holes one in the top spacer bar and one in the bottom then blasting in some warm air to dry things out then re-sealing.

Answer 1

Personally I think you will just be wasting your time.

When a sealed unit has failed the perimeter edge sealant is allowing air to enter the cavity between the glass this in turn takes moisture into the cavity.

When a sealed unit is first manufactured the normal method of construction is two sheets of glass with an aluminium spacer bar to hold the glass apart. The two longest lengths of spacer are filled with desiccant crystals, and the perimeter edge is sealed.(known as hermetically sealed).

When the sealant edge fails, for whatever reason, the moisture is drawn into the cavity and the crystals absorb the moisture. But, when full they cannot absorb any more moisture, so condensation is formed between the pains. The initial job is to de hydrate the air trapped in the cavity when first sealed.

hope this gives you an insight as to what you are trying to reverse.


Answer 2

I agree with the above, whatever "miracle cure" you try will only ever be short lived.

Just in case anyone else was thinking about messing about with blown double glazed units, don't bother! The cost of replacing them may be much cheaper than you think. I was very surprised as I thought I would be looking at twice that amount.

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