Black Knight Secondary Glazing
Black Knight Secondary Glazing

About Condensation

Many people experience condensation and the resulting mould growth in their properties but if you can understand what causes it and why you can begin to control its effects.


There has been a considerable amount of research done over the years to investigate the causes. Studies have shown that fitting secondary double glazing is one of the most effective ways to eliminate the problem.


When does condensation occur?

  • whenever moist, warm air, encounters a cold surface
  • more likely during the colder months particularly at night

Why does condensation occur?

  • Water vapour from breathing - one person breathes out about half a pint of water every hour
  • Over three quarters of all damp problems in buildings is caused by human activity and the effects of condensation 

Why does condensation appear on windows?

  • Although you can see condensation on windows it is also on surfaces such as walls floors and on furniture – it just isn’t as visible as on glass
  • Radiators below windows cause warm air to rise and condensate on colder glass particularly in a bedroom

The important factors in controlling and eliminating this are proper insulation, reducing excessive moisture, adequate ventilation and heating levels

It is important to realise that some buildings are more prone to condensation than others – construction type is a big factor

Controlling condensation

  • Adequate insulation prevents expensive heat from escaping
  • Ensuring sufficient background ventilation particularly in areas of higher humidity such as kitchens and bathrooms to regularly change saturated air with unsaturated air

Severe condensation problems and dampness


If you are suffering severe condensation or dampness it is important to find out if there are underlying structural defects.

Additional information

  • more information about condensation control
  • all the causes of condensation