External Condensation
This problem tends to raise it's head in Spring and Autumn, and only when particular temperatures and climates collide
It's a natural phenomenon and doesn't affect the performance or longevity of the windows and doors at all. It's is, put simply, a bi-products of todays more thermally efficient glazing - and as our glazing continues to improve, it is likely more people will experience this issue
Pilkington, one of the world's largest glass suppliers, talks about external condensation like this
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 glassis, 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. |
Can anything be done about it?
Well some innovate products have been released by Pilkington and Planitherm / Saint Gobian - however it costs more, and doesn't seem to sell (currently) in high enough volume to test its performance in the real world - only time will tell
The trick is to know that the problem exists, that it isn't causing any damage, is temporary and just proves you have well insulated windows
Read about Internal and External Condensation at http://www.heronhurst.co.uk/condensation which includes a downloadable comprehensive information booklet produced by the GGF - The Glass and Glazing Federation