DON’T PANIC IF YOU SEE CONDENSATION ON THE OUTSIDE OF YOUR WINDOWS – this means your energy efficient glass is working!
Twice a year, during Spring and Autumn, you are more likely to see condensation forming on the outside of your windows, usually first thing in the morning, only to clear by around midday. So why is this?
Moisture condenses out of the air onto a cold surface that is said to be below the dew point. The dew point varies with the air temperature and the amount of moisture it contains. Particularly in spring and autumn, the glass temperature can fall to a low level during the night and the dew point can be comparatively high in these seasons. The glass temperature can be below the dew point under these conditions and moisture can condense onto the surface, usually in the central area of the pane.
The windows we fit in our homes are now much more thermally efficient than in the past. Here at Harp, we install Planitherm Energy Efficiency sealed units as standard. However with single glazing and older style double glazing, a large proportion of heat was lost to the outside through the glass. With modern low emissivity glass, more of the heat is kept inside and the outer pane is not heated as much.
The more thermally insulating the glass is, the lower the outer pane temperature is likely to be and the greater the risk of condensation on the external surface.
You may notice that not all of the panes are affected by early morning condensation, even in the same window. Subtle differences in orientation and the position of objects outside the window can change the surface temperature of the glass to the point that one pane suffers and another does not. Any object such as a canopy or tree blocking off the window to a clear night sky will also reduce the effect.
A plus point is the knowledge that your windows are keeping the heat in as they are designed to do, proving that you have a superior insulating glass product.
For further in-depth information about condensation, the different types of condensation and causes of condensation, please see the Saint Gobain main website (St Gobain manufacture Planitherm glass).