Condensation Explained

Condensation, both internal and external, on glazing is a regular complaint by homeowners. The condensation does not come out of the glass and is not caused by windows.Essentially, condensation results from atmospheric moisture vapour turning into a liquid and depositing onto impenetrable surfaces. This is increased when temperatures fall – typically in winter. The glass presents the ideal surface for moisture vapour to condense upon, as it is generally colder than other areas of the fabric of the building.It needs to be accepted that the moisture vapour and, thus, the condensation is already present in the building; it is more the conditions that allow condensation to form that must be addressed. Some basic steps can be undertaken :

• Increase ventilation.
  • Open trickle vents in moisture-producing rooms
    • Kitchens & Bathrooms
  • This can also be done by opening bathroom windows after use.
  • I am using extractor fans effectively – setting extended time before auto switch off.
  • Using extractors in kitchens when cooking
    • An open window on to vent also for boiling water type
• Increase internal temperature
  • Warm air holds more water vapour than cold air; thus, warmer air means less condensation.
    • Currently, with excessively high energy costs, home heating may be restricted, which increases the likelihood of condensation forming.
• Reduce moisture vapour production.
  • Do not dry clothes on radiators.
  • Reduce usage of gas fires – burning Methane (natural gas) produces moisture vapour.
    • Many homes have gas fires, which may seem more economical than using the full heating system.
  • Have windows on to vent in bedrooms at night, as breathing produces water vapour!

Modern buildings are more airtight with ventilation measures built in. However, they also use much water during construction – e.g. newly plastered walls & solid concrete floors. This water may take time to evaporate entirely, and condensation would generally reduce as the building ages. Likewise, new decorative works and building projects may use water in existing homes, creating additional moisture vapour for some time.In summary, ventilation and warmer room temperatures will reduce condensation that appears on the glazing. Windows do not cause the problem, but the result is seen in windows.As a comparison and demonstration that condensation is not the windows' fault, if one removes a bottle of beer, wine or milk from the fridge and places it on the kitchen counter, it will soon have moisture condensed upon it. Where has this moisture come from? It hasn’t leaked out of the vessel; it is not beer, wine or milk; what is it? It is moisture present within the building condensing onto the calm surface.Condensation may seem more prevalent in some buildings than others, but the root causes are the same - lack of ventilation and low temperatures. If conventional corrective measures, some described above, are not sufficient to reduce condensation to acceptable levels, mechanical extraction in the form of a dehumidifier may be required. This may only be needed when condensation is at its worst for any given situation.