Why does my New Double Glazing mist up on the outside?

Have you ever wondered why some of your windows get foggy when it’s chilly outside and cosy inside? It’s not because they are feeling cold or shy. It’s because of a natural process called condensation.

Condensation is when water vapour in the air turns into liquid water droplets on a surface. It happens when the air is moist and the surface is colder than the dew point temperature of the air. The dew point temperature is the temperature at which the air can no longer hold all the water vapour it has and some of it condenses.

Condensation on the outside pane

If your windows are made of energy-saving double glazed glass, this means they have two or more panes of glass separated by a layer of gas or air. This layer and the coating on the glass act as a cosy blanket and stop heat from escaping from your room to the outside. Although it might seem like a slight drawback, it’s actually good for your comfort and your wallet, as it lowers your energy bills.

When it is cold outside and warm inside, the temperature difference between the two sides of the window increases. This can make the outer pane of the window very cold, especially at night or in winter. If the air outside is damp, such as after rain or snow, it can reach the dew point temperature on the cold surface of the outer pane and form condensation.

But don’t fret, this is not a sign of a problem with your window. It is a sign that your window is doing its job of keeping the heat in. It also means that the air inside your room is relatively dry and comfy. Condensation on the outer pane of your window usually goes away when the sun comes up and warms up the glass or when the outside air becomes drier.

Condensation on the inner glass pane

Condensation on the inner pane of glass facing the inside of the house (one which you can wipe away), is a sign that the room is quite humid, this can be caused by things like our breathing at night time, drying wet clothes on a radiator in close proximity to the window, or even something more serious like water getting in between the frame and brickwork making the walls damp. This means the window would need re-sealing properly.

Condensation between the 2 panes of glass

However, if you see condensation ‘between’ the two panes of glass (one that you can’t wipe away), it can mean that the seals on the window are broken, letting moist air enter the space between the panes. This can reduce the performance of your window and cause damage to the frames and the walls. To prevent this we would recommend that you replace your glass unit with a new replacement glass unit.

Why don’t we have a Condensation problem on other glass units?

You may notice that other glass units don’t have the same condensation issue as your new state of the art energy saving glass, this is because the glass units that don’t suffer from this phenomenon are very likely to be double-glazed glass that doesn’t have the special energy-saving benefits or special coatings. They let heat out more quickly and therefore don’t contrast the difference between the warmth inside and the cold outside quite as well as the latest energy-saving glass units do..

It’s highly likely that these units are just standard glass units with no extra energy-saving benefits. In this case, it is recommended that you replace these ones with energy-saving glass as well, to make your home more toasty warm in the winter and cooler in the summer.