Sleeping While The Rest Of The World Doesn't

Prevention and treatment of condensation in your double-glazed windows

Double glazing is an excellent way of keeping your home insulated. However, there are a few things that can go wrong with them, and one of these is condensation in the air gap between the two panes.

The problem

Condensation occurs when warm air from the room enters the gap between the panes and meets the cooler air within. It condenses, leaving moisture on the surface of the windows. As well as forming a mist on the window that can interfere with the view, it can also lead to black mould and even cause dry or wet rot on the wall below.

The cause

Condensation usually occurs in double-glazed windows when the seal around the panes has deteriorated so that air can pass through. By and large, the better quality of the windows in the first place, the longer the seal will last, but it is likely to degrade and crack sooner or later. As well as causing problems with condensation, this also means that the heat from your home will be leaking out.


It is much easier to prevent condensation than it is to treat. Your best line of defence is to detect the gaps in the sealant before the moisture has had a chance to collect in the windows. Do this by regularly running your finger around the seals to ensure they are intact. If you feel any breakages or gaps in the sealant, it should be repaired as soon as possible.

You can also try to reduce the amount of moisture in your home in the first place. Ensure that everywhere is well ventilated, and consider investing in a dehumidifier to remove the moisture from the air.

Treating condensation

If you have condensation in your windows, you will need to repair or replace them. Repairing can only be done by a specialist, and involves drilling a small hole in the window, using a desiccant to completely dry it out and then re-sealing the unit. Although this should be cheaper than replacing the windows, you should ask yourself if they are coming to the end of their life anyway, and if it might be cheaper in the long run to replace them.

Preventing condensation is far cheaper and more effective than trying to treat it. Check your double-glazed windows regularly and reduce moisture in your property, and they should keep your home warm and attractive for many years.