condensation on glass panels

Condensation is a natural occurrence and can appear on all types of glass panels. Whether they are external or internal, it can occur when moist, or humid air comes into contact with the colder surface. The low thermal mass of the glass means it cannot hold heat and is usually cold to touch.

Unfortunately, condensation tends to be more prevalent in the winter season when it is colder outside, and the windows and doors are closed to retain the heat in occupied properties. Because of this, it is paramount when considering glazing all projects must consider ventilation, this is key to removing any moisture build-up within the home.

Traditional single glazed units will of course have the most condensation appearing on the glass, as the glass is as cold on the inside as the outside. With the recent introduction of double and triple glazed units, condensation has reduced. However, occasional condensation can still form, as described below.

Internal condensation

With recent insulation requirements for glazing efficiency, the internal pane of the glass can have condensation issues. This is due to the temperature variation between the external and internal environment.

Water droplets occur depending on how much moisture there is in the home. For example, the steam from a kettle, drying washing, cooking, plants, or shower will naturally be absorbed into the air. When this water vapour comes into contact with a colder surface the air will be chilled.

Double and triple glazing can help to reduce the amount of condensation on the windows. However, it cannot completely eradicate the issue. If the air temperature within the room is low (not heated) and not well ventilated the air reaches a point when it becomes too saturated. This cooler air meets the colder internal glass and vapour will turn back into moisture. When this happens water droplets will appear on the glass. 

External condensation

Fortunately, when external condensation appears on the outside of the glass it is not a sign of poor performance. It is actually a positive sign that your glass windows, doors, or roof lights are doing a good job. In fact, the purpose for which they were designed.

With modern glazing efficiencies, maintaining a comfortable internal temperature, saving on energy costs, and meeting building regulations windows and doors are more thermally efficient.

The more highly insulated your glass is, the greater the likelihood of external condensation forming on the outside of the glass. With modern low/e (emissivity) glass heat is retained within the room and not lost through the glass. The internal panel is considerably warmer than the outer panel compared to single or old double-glazed units where the temperature differences are not as great.

Internal cavity condensation

Having condensation on your glass is perfectly normal, as pointed out above. However, having condensation on the inside of the cavity within the glass is not. If this happens unfortunately the glass cannot be fixed and will need to be replaced. 

The manufacturers guarantee should cover this within the guaranteed period. New glass will need to be ordered and installed, outside of the guarantee this will be chargeable.

How can I stop condensation on my glass panels?

If you have vents on your windows or doors try and keep them open to ventilate the space. Also, make sure doors are kept shut when taking a shower, cooking, or even boiling the kettle, and use a fan to reduce the levels of vapour in the room.

Using an air-conditioned unit can help to dry the air in the room. By using a dehumidifier or a moisture eliminator it should remove the main cause of condensation.

Plants are a wonderful addition to any room but unfortunately, they add too much moisture into the air. If you want to avoid this happening it would be wise to move them to a more suitable well-ventilated room during colder seasons when external temperatures are significantly different from the internal temperature in the room.

For more information view the Glass & Glazing Federation website.