Noise and thermal insulation

No more moisture with thermal insulation glass!

Condensation happens when moisture in the air suddenly cools and condenses on a cold window.

Although it is difficult to prevent this on the outside of a window, by installing well insulated double glazing window (Low E), condensation problems on the room-side can be greatly reduced. As the room facing pane of an insulated double glazing window stays warmer, the air that comes into contact with it does not cool and condense.
There are three main ways to improve thermal insulation, and thus reduce condensation, in a double glazing window :
- By using Low E glass
- By upgrading from an aluminium edge spacer to a warm edge spacer bar
- By substituting a dehydrated air cavity filling with an inert gas, such as argon

In a properly sealed double glazing window there should be relatively little condensation in the window’s inner cavity as dehydrated air and desiccants are used. If there is condensation in the double glazing window's cavity, this is probably due to a seal failure.

What is condensation?

Condensation is defined as the physical process by which a gas or vapour changes into a liquid. If the temperature of an object (e.g. grass, metal, glass) falls below what is known as the ‘Dew Point’ temperature for a given relative humidity of the surrounding air, water vapour from the atmosphere condenses into water droplets on its surface.
This "dew point" varies according to the amount of water in the atmosphere (known as humidity). In humid conditions condensation occurs at higher temperatures.
In cold conditions condensation occurs despite relatively low humidity.

Indoor condensation

The principal cause of condensation on glass on the inside of a building is a high internal humidity level coupled with a low outside temperature which cools the inside surface to below the dew point, particularly around the edges.
Bathrooms, kitchens and other areas where humidity levels are high are particularly susceptible to this problem.

Ways of controlling indoor condensation :

In order to control this form of condensation, consideration should be given to improving the heating and ventilation in these areas. However, another way to reduce the problem is to use high performance double glazing window containing an enhanced thermal insulation glass.

Windows manufactured using an energy efficient low-emissivity (or low-E) glass actually restricts heat exchange across the air space between the two panes of glass. This keeps the inner pane of glass warmer thus reducing the instances when condensation can form.
In addition, the use of a "Warm-edge" spacer bar made of insulating material will reduce the risk of condensation at the edges.

Outdoor condensation

Condensation forms on the outdoor surface of glass when its temperature drops below the outdoor dew point temperature. Again, windows manufactured with a double-glazing window containing energy efficient low-emissivity glass, have enhanced thermal insulation properties thanks to a high performance transparent coating that reflects heat from radiators or fires back into the room.
As a result the outer pane of glass does not get warmed by heat escaping from inside the building through the glass and remains cooler in comparison to less efficient thermal insulation glass.

External condensation only occurs in certain climatic conditions with high humidity levels and/or particularly cold weather. It is possible that external condensation will appear on some windows but not on others.
This is due to localised atmospheric conditions such as shelter from nearby trees or buildings, variable air currents and wind speeds and varying levels of nearby vegetation.

Condensation on insulating double glazing window

Condensation on the outdoor surface of such high performance windows is in no way an indication of a defective unit. Indeed, this can be seen as a positive indication that the enhanced thermally insulating double glazing window are actively reducing heat loss through the glass (see table overleaf).

This form of condensation can be counteracted through the use of a hydrophilic coating such as traditional self-cleaning glass. Traditionally a self-cleaning glass attracts water across the surface in a "sheeting" effect allowing clear vision through glass that is susceptible to external condensation.

Defective Units

The formation of condensation on the inner faces of the double glazing window is an indication that the air or gas cavity is no longer completely sealed. The desiccant will rapidly become saturated and any damp air penetrating via the seal around the perimeter will reduce visibility by forming condensation on faces 2 and 3.
The double glazing window must therefore be replaced as this cannot be reversed. This double glazing window must be replaced in accordance with the terms and conditions of the warranty.

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