Damp and condensation-the facts

Damp is unhealthy. It makes you feel colder. The black mould that grows on damp surfaces can cause respiratory problems, as well as looking unpleasant. And clothes can get spoilt by mould if they’re damp.


Water gets into the air from:

  • Breathing and sweating
  • Cooking
  • Drying laundry
  • Washing, bathing and showering 

Damp gets into your house because:

  • It condenses out of the air
  • It comes though gaps and holes e.g. slipped slates on the roof
  • It comes through the walls or up through the floor, for example if the damp course is faulty or an overflow keeps dripping.


 Black mould grows where surfaces are often damp.

Sometimes it’s clear why – we all get black mould round the sink, basins and shower tray.

On walls and windows, it’s usually from condensation of water out of the air – this happens when the air is damp and surfaces are cold. That’s why it happens most on cold uninsulated outside walls, at the bottom of cold window frames, and in corners and the back of cupboards where there’s  no air movement to dry it.

Taking action

Obviously, first fix any problems with the building and its plumbing which are causing leaks 

After that, there are three ways to tackle it:

  • Change your habits so less water gets into the air
  • Have more ventilation to move air around.
  • Make cold walls warmer
1.  Change your habits
  • Keep the lids on saucepans.
  • Dry clothes outside.
  • Dry washing in one room upstairs with the door shut and the window open. (Tumble driers use a lot of electricity and so are expensive to run and cause global warming).
  • Shut the bathroom and kitchen doors when you’re using them, and for a while after.
  • If you have mould in your wardrobe, move it away from an outside wall.

2.  Increase Ventilation

Many older houses have more than enough ventilation anyway through gaps and cracks! If not:

  • Install – and use - extractor fans in the bathroom and kitchen.
  • Keep windows open.
  • Keep window vents unblocked.

3.  Make cold warmer

  • Check your loft insulation is 10 inches deep and reaches into all the corners to avoid cold patches in your ceilings.
  • Double or secondary glazing reduces condensation and mould growth, as well as keeping you warmer and cutting your bills.
  • Insulate cavity walls. 


Home Energy – Damp and Condensation (L0)                                     WinACC May 2016


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