Condensation Control


Condensation Control

What is Condensation?

Condensation occurs when water vapour changes state and becomes liquid, the opposite of evaporation. This happens when humid air cools and water vapour condenses into liquid water droplets. It can also happen when the air becomes too humid, beyond its saturation point.

Condensation is a key part of the water cycle, forming water droplets in clouds when warm and cold fronts meet.

Condensation can also occur when warm and humid air meets a cold surface, such as a window or wall within a home and can affect homes of all ages and sizes especially during the winter months.

Many homes in Scotland experience issues with condensation, damp, and Black Spot Mould. As condensation can cause damp and Black Spot Mould conditions within houses, it is important to take steps to address the problem.


  • Around 20% of homes both old and new are affected by condensation or Black Spot Mould.
  • Untreated Black Spot Mould can trigger respiratory problems.

Condensation – what to look out for

All properties are different and the reasons that they are affected by Condensation or Black Spot Mould will also be different and issues will display differently.  Any of the issues below may indicate the presence of Condensation:

  • Water gathering on the inside of your windows or at the windowsill 
  • Water gathering on surfaces such as kitchen/bathroom tiles
  • Growth of black mould on walls, ceilings and skirting
  • Peeling of wallpaper or deteriorating paintwork
  • Mould growing on clothes or stored articles
  • A strong musty smell

For condensation to occur, the air must have some degree of humidity. Cooking, boiling the kettle, drying clothes inside, and running a shower are all causes of humidity within households. Even the act of breathing releases water vapour into the surroundings. A lack of ventilation may worsen the humidity level of this warm air, increasing the likelihood of condensation occurring.

Simply put, humid air cannot escape if there is not adequate ventilation. The result being that the warm air may cause condensation in the colder areas of the house.

Condensation is much more common in the winter months for a range of reasons. Householders may keep windows closed to keep out the cold and are much more likely to dry washed clothes inside. This both decreases ventilation and increases moisture within the house. Improving ventilation can help to decrease this damp, stale air.

Central heating will raise the temperature of the air within the home, in contrast to the cold air outside and any unheated spots in the house will likely be very cold in the winter too. This can result in condensation occurring on cold windows, or unheated interior walls. High levels of condensation can cause significant areas of damp and a whole host of issues.

Condensation Solutions

To lower the chance of Condensation forming we recommend the following:

  • Ensure the affected property/room is adequately ventilated. i.e., Open trickle vents at window area for a few hours each day at the very least.
  • Ensure the property is adequately heated. This is especially important throughout the winter months.
  • Refrain from drying washing on radiators or anywhere inside if possible.
  • Refrain from cooking or showering without proper ventilation.

Extractor fans are commonly installed in kitchens and bathrooms to combat condensation. They help to get rid of excess humid air at the source, stopping it from being dispersed across a house or property.

We can assist with the installation of extractor fans, if required.  Please request an appointment with one of our surveyors for further advice.

For more serious cases of condensation, we may recommend the installation of a Positive Input Ventilation (PIV) Unit.  These come in a variety of options to suit your property and can be used in houses and flats. PIV units work by drawing air from the outside, where it is filtered before being passed through a modern ceiling diffuser. Please request an appointment with one of our surveyors for further advice. (Book a survey button)

Black Spot Mould

Black spot mould is a fungus (Aspergillus Niger) which forms as a result of condensation. Black spot mould usually appears in areas where there is very little air movement such as window reveals, floor / ceiling and floor / wall junctions and behind furniture that is positioned behind colder walls.

Once steps have been taken to combat the cause of the condensation you should attempt to clean the areas affected by Black Spot Mould.  If left untreated the black spot mould spores can cause health issues such as allergic reactions and respiratory problems.

We can supply a Mould Eradication Kit which can be used to clean the affected areas and when applied to paint, as directed, can stop mould reforming.

If you are interested in purchasing a Mould Eradication Kit, please get in touch to order

Further information on dealing with condensation can be found in this booklet – PCA Condensation Leaflet