Condensation, mould and damp

Most of us create at least 4 pints of moisture per day just by breathing, cooking, bathing, washing and drying clothes - normal everyday activities that everyone performs at home. When temperatures drop, the air can no longer hold onto all the moisture generated; it will migrate to the coldest parts of the house and condense onto the windows and walls. 

When levels reach 70% humidity, mould will start to form but also conditions are ideal for dust mites both of which are known triggers of asthma and allergies. This is why problems occur during the winter rather than the summer.

So how do you spot condensation?

  • Streaming windows and walls
  • damp areas can appear on walls, especially behind furniture and in corners
  • wallpaper can start to peel
  • mould growth, usually black mould, starts to appear on window frames, walls and ceilings
  • soft furnishings and fabrics become prone to mould and mildew
  • there is a constant musty damp smell in the property 

An ideal balance would be for a property to maintain a constant level of warmth through adequate building design, insulation and heating, whilst ensuring that any moisture produced by the occupant can be quickly removed through adequate ventilation. 

By affecting one of these issues you may improve or cause deterioration to the conditions. Practical difficulties such as increased heating costs can prevent this from happening.

For more practical advice on how to reduce concentration:

Tips for tenants on how to reduce moisture in the air

  • keep the inside temperature reasonably constant for as much of the time as possible. A healthy indoor temperature for a living room is 21 °C for other rooms 18 °C other areas and 22 °C for bathrooms.
  • avoid drying clothes indoors.  If you have no choice place the clothes rack in a well ventilated room keeping the door shut
  • ensure that any tumble drier is externally vented or the condensate reservoir regularly emptied
  • keep furniture away from walls
  • do not disable any extraction units
  • open windows and close doors when cooking and taking showers/baths 

Tips for landlords on adequate insulation, heating and ventilation

  • ensure every room has adequate heating to prevent creating a cold rooms. See above for a healthy indoor temperature.
  • ensure there is a means for rapid ventilation at times of peak moisture. Such as an extract system in the kitchen and bathroom.
  • ensure the property is adequately insulated. Cavity wall insulation and loft insulation will ensure that heat does not just escape and property is affordable to heat. 

Landlords have a responsibility under the Housing Health and Safety Rating System (HHSRS) to assess hazards and risks within rental properties. 

Local authorities are under a duty to take action against Category 1 hazards which include damp, mould growth and excess cold.

Further information

You can speak to our Environmental Health Technical Support team about any of these concerns by:

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