Fitting modern low-emissivity glazing does increase the chances of external condensation but this is not a fault in the glass or the windows. The phenomenon is a natural and predictable event caused by the outer pane of the glazing being colder than that of the glass that it replaced. With single glazing and old double glazing a larger proportion of heat was lost to the outside through the glass. With modern low-e glazing more of the heat is kept inside and the outer pane is not heated as much.

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. In Spring and Autumn in particular 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 is more often likely to be below the dew point in these conditions and the moisture condenses onto the surface.

Energy Efficient Windows

We are all obliged to fit more thermally efficient windows and glazing in our homes to comply with the latest Building Regulations. The trend is to use glass that has lower U-values thus providing better thermal insulation and, the lower the U-value, the lower the outer pane temperature is likely to be and the bigger the potential of condensation on the external surface. In northern European countries where the weather is much colder, glazing with very low U-values is a must and the phenomenon is understood and accepted. These householders are focused on saving energy and maintaining a comfortable internal environment.

In the vast majority of cases the condensation does not last long. A little heat from the sun warms the outer glass enough to evaporate the moisture and a gentle breeze or wind will do the same job.

You may notice that not all of the panes are affected by early morning condensation even in the same window. Even 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 (be it an overhang, canopy, tree etc.) blocking off the window to a clear night sky may also have the effect reducing the occurrences.

A plus point is the knowledge that your windows are keeping the heat in as they are designed to do thus proving that you have a superior insulating glass product. The presence of external condensation in a particular season does not mean that the glass will suffer the same throughout the year. Any occurrence is beyond the control of the window supplier and is a natural result of the environmental conditions.

If you are experiencing condensation to the inside of the room or there is condensation between the panes of glass then that is a different problem. Misting between the panes indicates a seal failure and the glass should be replaced. Misting inside the room may be as a result of a failed unit seal but is more likely to be the humidity or moisture content of the air in the room being very high eg. from a bathroom or kitchen. Bottled gas and paraffin heaters produce a lot of moisture and even breathing expels enough moisture in an unventilated space to cause the formation of condensation. Increasing the ventilation to such spaces helps control the problem.

Another First From ENERGLAZE

If you are one of the unlucky ones that suffer from prolonged external condensation as a result of highly efficient glass panels and the condensation stays for long periods then we have a product to help eliminate the problem.

NEW PILKINGTON ANTI-CONDENSATION GLASS – The solution to external condensation.

Pilkington Anti-condensation Glass is used on the outer pane of the double glazed unit. It provides a second low-emissivity glass which is designed to delay the onset of external condensation and hence improve the view through the window. As with most ENERGLAZE products there is no need to change your window frames just the glass.

ENERGLAZE are the first company in Ireland to offer Pilkington Anti-Condensation glass as a solution to external condensation on glass. And remember there is no need to change your window frames.