Window Condensation

During certain months of the year, here at Walkers, our staff receive many phone calls and emails in relation to condensation – namely from customers who have just had some fabulous brand new, A-rated windows installed.

Condensation is often associated with old, thermally inefficient windows but that’s due to the common myth that new A-rated, double glazing will completely eliminate it. While we can understand some of our customer’s concerns, here’s your guide to condensation and why there is really nothing to worry about. In fact, if anything, a little condensation means that your new windows are doing their job properly!

Internal condensation

Internal condensation can be caused by a whole host of human activity and usually as a consequence of a ventilation problem rather than a fault in your double glazing. It is worth noting that it cannot be caused purely by the installation of double or triple glazing.

However, internal condensation can become a real problem if left alone as it can lead to damp problems which in turn will allow mould to develop, wallpaper to peel off and damage furnishing.

General day to day activities that cause internal condensation are:

  • Breathing: (Yes, really!) two sleeping adults produce approximately 1 litre of moisture in 8 hours, which is absorbed as water vapour into the atmosphere and can add to internal condensation. Where you can, it is advisable to leave a window a jar while you sleep or leave your bedroom door open to allow the room to remain ventilated.
  • Cooking: steam created by saucepans, ovens and kettles may seem to disappear but they have to go somewhere – have been absorbed into the atmosphere. To avoid creating condensation, make sure you prop open a window or use an extractor fan whilst cooking.
  • Washing up, bathing, laundry: any activity that involves hot warms creates the vapour clouds given off by the hot water are rapidly absorbed into the atmosphere. If you’re leaving damp clothes to dry or enjoying an indulgent bath, keep the room ventilated with extractor fans or open windows.
  • New property: the bricks, timber, concrete and other materials in an average 3 bedroomed house absorb about 7000 litres of water during construction. Much of this is dissipated into the indoor atmosphere, thus creating condensation.

External Condensation

According to the Glass and Glazing Federation, “Due to recent innovations in the efficiency of double and triple glazing, along with updated requirements of building regulations and the lowering of carbon emissions, certain weather conditions may allow the formation of external condensation on energy efficient windows and doors. This is a natural phenomenon and a clear indication that the window or door is preventing heat loss from your house.”

Condensation forms when the temperature on the outside surface of the glass drops below the outdoor dew point temperature. Double and triple glazed windows contain energy efficient, low emission glass which boasts enhanced thermal efficiency which deflects heat from radiators and heaters back into the room. As a result, the outer pane of glass doesn’t heat up as the heat does not escape from the room – unlike with less thermally efficient windows. External condensation only occurs in certain climatic conditions – a variable combination of high relative humidity and clear cold conditions normally experienced in spring and autumn.

For more information on Walkers Windows high security windows and doors and energy efficient A-rated double glazing or if you’d like a free, no obligation quote – visit or contact us on 0800 849 222 9.