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Woodland Blog


It’s a curious thing and worth a mention, especially at this time of year. Condensation on the outside of a double-glazed unit is actually a sign that your windows are working really effectively.

There are three places on a double-glazed unit you will potentially find condensation; on the inside face of the inner pane i.e. inside the room, inside the cavity between the two panes of glass, and on the outside face of the outer pane i.e. outside your house.

Let’s take a moment to briefly explain all three.

Firstly, condensation on the inside face of the inner pane. This is very common on single glazed windows and is caused by moisture in the air coming into contact with a cold surface (the glass!). If your windows are single glazed there is probably only a 2-3mm pane of glass between you and the outside world (brrr!). Any moisture in the air is going to condense on that glass as soon as the outside temperature drops significantly. Moisture in the air is caused by a few factors, such as people inside breathing, having showers /baths, hanging out washing etc. This is exacerbated if you don’t have adequate air exchange or poor ventilation. So, if you sleep in your bedroom in winter with the windows closed, you are likely to wake up with water pouring down the windows panes. A similar effect can be seen on older double-glazed windows. Condensation on the outer pane is a similar principle but in reverse, and we will look at that in a moment.

It’s worth mentioning that modern double glazing should eliminate much if not all of any condensation on the inner pane. Depending on air flow and environmental conditions, there is always a chance of a little condensation, but you should find that new windows suffer from condensation much less than older /single glazed windows.

The second type of condensation is caused when moisture gets into the cavity between the double glazing, and this signifies a breakdown of the unit. This usually manifests itself by a misty looking patch that comes and goes at different times of day and in different conditions. If not dealt with, over time the misty patch will likely leave a residue on the inside of the glass where moisture has evaporated and left mineral deposits behind. If left unattended the moisture will continue to build up and it looks quite unsightly. It is worth having a glazier replace the panes. At Woodland we have spent many years developing our glazing system so the chances of any unit breakdown is minimal, but for piece of mind all our units are guaranteed for 10 years against this type of failure, so in the unlikely event of this happening we would pop out and replace the pane if required.

So, on to phenomenon of condensation manifesting on the outside face of the outer pane. Firstly, if this happens to you, don’t worry! It is likely you have recently had your windows or doors replaced and it shows they are doing what they should be doing.

Modern double-glazed units incorporate technology that wasn’t around when double glazing first became common-place. We don’t know how other people make their units, but as a guide, double glazed units made here at Woodland use the latest thermally coated glass on the inner pane, warm-edge spacer bar, and Argon or Krypton gas-filled cavities. We could go into detail about all these facets, but suffice to say for now that the result is a very well insulated glazing surface.

In the depths of winter when you are snug and warm in your home (with your beautiful new Woodland windows of course!), you may find that the inner pane is quite warm, as it is being warmed by your heating etc. However, because of the coatings and the gas-filled units, this heat is not able to escape as quickly. In fact it can’t even reach the outer pane to any great degree. This means the outer pane remains very cold. Because the outer pane stays cold, in certain conditions you may find that moisture-laden air the comes into contact with the glass, then condenses on the outer pane as it is quickly cooled.

To summarise, if you do find condensation on the outside, don’t be alarmed, it is just a sign your windows are keeping you warm on the inside.

If you would like to find out more about how Woodland of Kingston can help keep your home warm this winter by installing new wooden windows and doors, give us a call today, we will be happy to help.

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