Blog Items

Blog Post

External Condensation

17 Sep 2012

We often get asked about external condensation as there is a common misconception that it is caused through a fault in glazing units. Condensation, a natural occurrence, can occur on the external surface of double glazed units, especially as winter approaches. To help explain, we investigate the causes below.

What Causes External Condensation?

Condensation is caused when the outside temperature of glass is lower than the temperature inside. Cold nights and dropping temperatures result in the formation of water vapour on the external outer panes of windows.

Moisture condenses out of the air onto a cold surface at what is known as dew point. The dew point temperature is the temperature at which the air can no longer "hold" all of the water vapour which is mixed with it. Some of the water vapour at this point must therefore condense into liquid water.

Typically in the spring and autumn months the dew point can be comparatively higher, causing condensation to occur more regularly.

Condensation and Modern Glazing

Condensation on the external surface is becoming more common as the types of glazing units being fitted into homes today are much more thermally efficient than in the past. The more thermally insulating the glass is, the lower the outer pane temperature is likely to be and the greater chance condensation will occur on external surfaces. With traditional style single glazing and older style double glazing, a large proportion of heat was lost to the outside through the glass.



There is not much that can be done to prevent external condensation. A plus point is the knowledge that the glass is keeping the heat in as it is designed to do, demonstrating that you have a highly thermally insulating product.  In many cases the condensation does not last long, as a little heat from the sun will warm the outer pane of the glass enough to allow the water to evaporate. However one of the major benefits of energy efficient double and triple glazing is the reduction or in most cases the total removal of internal condensation when compared to single glazing.

Pilkington Activ™

Those people who have fitted Pilkington Activ™ self-cleaning glass may also notice that they get fewer occurrences. Pilkington Activ™ is best suited to tackle condensation, with its properties that allow beads of water to form on the surface of the glass, and run simply off.

For information on Pilkington Activ™ and its self-cleaning properties please visit our official website or click here.