Helpful tips on how to reduce problems in your home caused by

Condensation and mould


All properties can get condensation and mould

We’re all able to reduce the amount of condensation in our homes by learning what it is, finding out what causes it and how we can reduce it.

Here we explain how mould and condensation can occur, and what you can do to prevent it from affecting your home.

Condensation is...

There’s always some moisture in the air, even if you can’t see it.

Air is like a sponge; the warmer it is the more moisture it’ll hold. As warm air cools it can’t hold all the moisture it’s carrying and will deposit it as tiny droplets of water. These droplets, known as condensation, are most noticeable on cold surfaces or in areas where there is little movement of air.

Common places include:

  • Bedroom windows first thing on a cold morning
  • The bathroom mirror and walls after a shower
  • Kitchen windows and walls during cooking
  • On the inside of an external wall behind large pieces of furniture
  • Condensation is a common issue and is easily controlled. It’s created through our everyday activities at home from bathing to cooking and drying clothes. Even breathing adds some moisture to the air

What causes condensation?

  • Too much moisture being produced
  • Not enough ventilation
  • Cold surfaces
  • Poorly heated rooms

To help reduce and control condensation and mould in the long term you’ll need to review all of these issues.

First steps against condensation

There are some simple things you should do straight away when you notice condensation. Dry your windows and windowsills every morning with a cloth. You’ll also need to check and dry surfaces in the kitchen or bathroom as they may have become wet due to steam. Wring out the cloth rather than drying it on a radiator.

Effects of excessive condensation

If moisture has been present for a long time or condensation is excessive, mould may have begun to grow. If left untreated, mould will spread so it must be treated as soon as you see it. Mould can worsen existing respiratory problems, including asthma and bronchitis so it’s important you do this.

First steps to removing mould

Take a photo of the mould before you begin treatment. It will help you monitor your progress with controlling the cause, and confirm what changes you’ve made that are working.

In cases where you’ve tried everything to control condensation but you still notice mould, it’ll help Aster Group to confirm and resolve damp issues possibly caused by building defects.

To kill and remove mould, wipe down or spray walls and window frames with a fungicidal wash that carries a Health and Safety Executive (HSE) ‘approval number’.

Make sure that you follow the instructions for its safe use. These fungicidal washes are often available at local supermarkets.

You’ll need to have any clothes with mildew marks dry-cleaned and shampoo any affected carpets. Do not try to remove mould by using a brush or vacuum cleaner.

Ventilating your property

All properties will have some form of ventilation to help remove moist air and replace it with fresh air from outside. Ventilation is designed to keep your home fresh, healthy and comfortable. It’s typically installed as:

Extractor fans

Usually the ventilation in your bathroom and kitchen will be provided by an extractor fan. Some turn on automatically when you switch the light on, others a separate switch. Special fans designed to monitor moisture levels in the air can run all the time to maintain the air quality. Extractor fans cost very little to run over a year; about £8.

Trickle vents

These are installed to the inside of your window frames and must be left open where relevant.


You can also reduce the potential for condensation by ‘cross-ventilating’ your home for 30 minutes every day. You can do this by opening small windows on opposite sides of the house (or diagonally opposite if you live in a flat). You only need to open your windows to the first notch. It’s advised to open interior room doors to allow drier air to circulate throughout your home. Be careful not to ‘over-ventilate’ your home when it is cold, as it’ll cause the temperature inside to drop. Also make sure accessible windows will not cause a security problem and remember to close them when you go out.

Keeping warm

Condensation becomes less likely when your home is warm.

Condensation becomes less likely when your home is warm. The temperature of your home is affected by how you use your heating system and how well insulated the building is.

Heating one room to a high level and leaving other rooms cold creates and worsens condensation in the unheated rooms. It is better to have a medium level of heat throughout. If you don’t have heating in every room, you could keep the doors of unheated rooms open to allow some heat into them.

You may also want to consider using supplementary heating on a low setting. We recommend you don’t use bottled gas heaters as these create moisture. If you’re out the house all day you might want to consider keeping the heating on low all day in cold weather to control persistent condensation.

Keep a check on your energy costs if you choose either of these heating methods. We’ve got some simple ways to save energy in your home on page 11.

If you’re worried about heating costs we’ve included some useful contact numbers for companies who can help.

Reducing mould growth

Reducing mould growth After initially treating the mould we advise you redecorate using a good-quality fungicidal paint.

After initially treating the mould we advise you redecorate using a good-quality fungicidal paint, or if you’re replacing or hanging wallpaper use a fungicidal resistant paste, to help prevent mould reoccurring. The effect of fungicidal or anti-mould paint is destroyed if covered with ordinary paint or wallpaper

When to get help

Sometimes condensation and mould are caused by something more serious such as water getting into the building through a structural fault or a leak. For example, condensation doesn’t leave a ‘tide-mark’ around its edges on walls and is only present in cold weather. Some homes can also be effected by damp, which will need further to be investigated further to resolve.

Useful information:

There may be a time when you need to talk to someone about your energy costs or use. If you’re struggling to pay your bills always call your energy provider first. They’ll be able to check if your current tariff suits your needs and may also be able to check if you’re eligible for certain benefits that help pay towards your energy costs.

Here are some other useful numbers to call:

  • Advice on managing energy costs:
    Home Heat Helpline: 0800 33 66 99
  • Free, confidential and impartial advice on consumer issues:
    Citizens Advice Bureau (CAB) Consumer Line: 08454 04 05 06
  • Impartial advice on energy efficiency and sustainability:
    Energy Savings Trust (EST): 0800 123 1234

Further assistance

If your problems with condensation and mould persist after following these guidelines you can contact Aster to discuss the problems you’re experiencing and request a digital meter that measures the humidity in your home.

Contact us

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