Renfrewshire Council

Avoid condensation dampness

Condensation dampness is common in houses which are poorly heated and insulated.  

This problem can lead to staining and mould growth damaging wallpaper, walls, window frames, furniture and clothing.  

This produces higher numbers of dust mites due to the moist conditions and can also increase the risk of illness such as asthma and bronchitis.

This page tells you more about condensation, where it arises and how to tackle it.

What is condensation?

Air contains a certain amount of 'invisible' water vapour. The higher the temperature of the air, the more water vapour it holds.

Condensation occurs when air carrying vapour comes into contact with a cool surface. At this reduced temperature less water can be held and it is deposited. This is why the bathroom mirror steams up after a shower or a window when you breathe on it.

Where does condensation dampness occur?

The most vulnerable areas will either be rooms where a large amount of moisture is produced, i.e. bathroom/kitchen, cold surfaces in other rooms where this moisture can travel to. The effects of this may be visible, for example drops of water on gloss painted windowsill's, but often the water drops will soak into the wall and a problem will not be diagnosed until black mould patches start to appear.

Warm, moist air will move to colder areas in homes. For example, if the main living room is heated but the bedrooms are unheated.  When the warm moist air comes into contact with cold surfaces, condensation will form. 

The following areas are particularly prone to condensation:

  • Cold surfaces like mirrors, single glazed windows, and metal window frames
  • Kitchens and bathrooms
  • Walls of unheated rooms
  • Cold corners of rooms
  • Wardrobes/cupboards and furniture against an outside wall

How to tackle condensation dampness

The major difference between condensation and other forms of dampness is that you have the ability to reduce or solve the problem just through changing behaviour in the home. Try following these steps:

Reduce the moisture: Bathing, washing and cooking all produce moisture that can't be avoided. Simple changes are effective in tackling condensation dampness:

  • Keep lids on saucepans while cooking
  • Tumble driers should be vented to the outside
  • Avoid the use of bottled gas and paraffin heaters as these produce high levels of vapour
  • Dry washing outside when possible
  • When creating steam in the kitchen/bathroom open windows and close doors to these rooms.

Increase ventilation:  Ventilation does two things, it allows moist air to escape and increases the volume of air moving through the home.  Many houses have built in ventilation measures such as trickle ventilators and extractor fans. Here's some tips:

  • Kitchen and bathrooms with severe condensation problems should not be draught proofed.
  • Bedrooms should be ventilated at night.

Heating: Condensation is more likely to be a problem in homes which are under heated. Try to keep temperatures in all rooms above 15°C as this will reduce condensation forming on external walls.

Insulation: Following the steps on this page should reduce any condensation dampness problems you  have. If a problem still exists, insulating your home will have a threefold value in tackling the problem through:

  • Warming the surface temperature of wall, ceilings and windows
  • Generally increase the temperature of the home
  • Reducing heating costs - meaning the home is heated to a higher standard more affordably