What is condensation?

Condensation on double glazing or condensation on your window?

Condensation is the process by which water vapour in the air is changed into liquid water. Condensation generally occurs in the atmosphere when warm air rises, cools and loses its capacity to hold water vapour. The water vapour condenses on a cool surface to form water. This can easily be explained another way, when you take a cold drink outside in the summer, the outside of the glass gets wet with condensation, this is a normal reaction when warm air meets a cold surface. Condensation is crucial to the water cycle because it is responsible for the formation of clouds. Clouds produce rain, the primary way water returns to the surface. In short, condensation occurs naturally in our environment.

Condensation in the home

Condensation affects new and old buildings alike. As properties have become better heated and insulated the instances of condensation forming are on the increase. Older style houses were often built on suspended floors, had chimneys and were generally quite draughty! First evidence of condensation may be water droplets forming on the inside of the window pane, because the glass has a lower temperature than the fabric of the wall. Please remember the windows are not the cause of the condensation, they are merely an indication of a condensation problem. A family of four in a three-bedroom property can generate as much as 18 gallons of water per week as a result of cooking, bathing and by keeping house plants. With double glazed windows and doors and no ventilation this moisture becomes trapped within the property and can cause mold growth, commonly seen around windows and external corners of the walls.

Internal condensation is more likely in the winter months. This happens when moisture in the air contacts a surface whose temperature is lower than the dew point (the temperature in which air manufactures dew).

Can I treat condensation?

In short the answer is “No”. Condensation can only be controlled, but there are some steps that you can take to reduce your indoor humidity level.

One way is to make sure that all appliances requiring a vent (for example tumble dryers) are vented properly. Avoid using gas heaters (these produce a lot of moisture) and install extractor fans. Extractor fans are an excellent way to increase the air flow and reduce humidity if installed correctly. Areas that would benefit the most would be bathrooms and kitchens. Drying clothes on radiators, cooking and house plants all add to the moisture in the air. Bedroom windows attract condensation in the winter months because the average person expells over a pint of water while sleeping over-night. The mositure laden air will condense on the coldest place, this is usually the window.

Another option is to make sure that your home is properly vented. There are a couple of ways to achieve this desired effect. One solution for most cases would be to open a window in each room for a short period of time after use. When cooking then keep the kitchen door shut and ventilate the kitchen before opening the door, the same principle applies to bathrooms and shower rooms. This should stop the moist air spreading around the house.

Condensation on the external pane of glass?

The temperature of a typical double glazed window is usually above that of the exterior night time air because of the heat flow from the warm interior of the building. But if the unit has a very low U-Value (thermal conductivity) from the use of a low emissivity coating and Argon gas (like the ones used in KJM’s Energy Rated Windows) then on a still air night, the temperature of the outer glass surface can easily fall below the exterior air temperature or even its dew point temperature. When the glass temperature falls below the dew point temperature condensation occurs. This condensation will not evaporate until the glass is heated by wind, sunlight or heat transfer from inside your house. Our triple glazed windows will suffer external condensation, as they are very thermally efficient! In short the more efficient the windows are, the likelihood of external condensation will rise!

Condensation between the panes of glass?

Unfortunately this means the seal on the glass unit has failed. There is a process that enables this to be repaired (by a specialist contractor), however it will not remove the old water marks from between the panes. The easiest solution is to replace the glass unit, a very simple task on modern glazing that has a beaded system. KJM offer a free measuring and quoting service. All old glass units are sorted and skipped for recycling.

Further technical information from our manufacturer can be found on Condensation on Glass. Please also see KJM’s Blog article on Condensation.


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