Most homes get condensation at some time or other. But if it happens frequently and isn’t stopped, it can lead to mould growth and damp. Luckily, there are several ways to deal with it.

In this guide, we cover the causes of condensation and how to remove and prevent it. We also look at long term condensation solutions that can stop it coming back for good.

Condensation is water that collects on cold hard surfaces when warm air touches them. It most commonly occurs in winter on surfaces such as windows, doors and walls, and unventilated spaces, such as built-in wardrobes and cupboards.

Condensation can also form in rooms with high humidity, such as the kitchen and bathroom.

Condensation forms on windows when warm air from inside collides with the cold glass surface. When this collision happens, the air reaches its ‘dew point’, where the moisture held in the warm air condenses and merges to become visible water droplets.

Condensation on windows typically happens in winter because low outdoor temperatures make the windowpane colder, and heating makes inside air warmer.

You’ll also find that condensation on exterior windows is more likely to affect single-glazed windows than double-glazed ones. This is because double-glazed windows have an air gap between the two panes of glass, which act as a thermal barrier against the cold from outside. This means the inside windowpane stays closer to the indoor temperature. So, when warm air indoors touches the windowpane, it doesn’t reach its dew point. 

Single glazing doesn’t have this thermal barrier, which means the window’s surface will get a lot colder than the inside pane of a double-glazed window. Therefore, making condensation more likely.

Another reason windows get condensation is increased moisture levels in the air due to household activities. These include showering and bathing, cooking, drying clothes indoors and breathing. Two adults sleeping, for example, can expire up to half a litre of water, which is why bedrooms often have condensation on the windows in the morning. Plant pots and flowers in the home can also add to moisture levels.

Warm air holds more moisture, so condensation from these activities is much heavier. 

Double-glazed window panes are sealed units, and there should be no way air can get between the two panes of glass. So, if you find condensation between the panes of glass, then the seals have failed, and the windows need to be replaced. If the windows are new, they should be covered by a manufacturer’s warranty.

Condensation on the outside of windows

During summer, condensation can appear on the outside of windows early in the morning. This is due to humid outdoor air warming up quickly and touching the windowpane that’s still cold. This type of condensation is nothing to worry about, and it will clear on its own.

Condensation left on windows can, over time, lead to damage on both uPVC and wooden window frames. 

uPVC windows are designed to be hardwearing. But when the inside seals constantly flip between being wet and then getting exposed to intense sunlight, they expand and contract, making them dry out and crack. This can lead to the seals failing, so the glass will fog up between the panes, and the window will lose its insulating benefits.

This combination of alternating damp and strong sunlight also damages wooden window frames. The wood will dry and crack, and paint and varnish will peel. Over time, the window frame will deteriorate and will need to be replaced.

On top of this, both types of windows will be susceptible to mould growth and a build-up of limescale.

Condensation on windows is most likely to occur in rooms where:

• There is little or no ventilation

• There is a lot of humidity (such as in the bathroom or kitchen)

• Clothes are drying

• People are sleeping (the heat from respiration can cause condensation)

Mould and damp are caused by excess moisture in the air that has no way of escaping. Excess moisture can come from condensation left on a surface or steam created through showering, cooking or drying clothes.

Damp on walls can also be caused by structural problems, such as a leaking roof, failed damp-proof course, overflowing gutters or plumbing problems. If damp is left for more than 24 hours on a surface, mould and mildew form. 

Mould and damp can be prevented by using a dehumidifier, which we’ll cover later in this guide.

Here are 8 top tips to stop condensation on windows:

1. Open windows in bedrooms at night
   The warm air people breathe out while sleeping increases humidity. There's nowhere for the moist air to go when windows are closed, so it turns into condensation. Opening the window allows the warm air to escape instead.   
    

2. Keep curtains open in bedrooms at night
   Closed curtains are great draught excluders, but they also prevent the windowpane from being warmed up by central heating. This makes the glass colder than it could be, therefore causing condensation. Keeping curtains open at night means the glass temperature will stay closer to the room temperature so condensation won’t form. If it’s not practical to keep curtains open, changing them to thinner curtains will still make a difference. 
    

3. Open windows in bathrooms when showering or bathing
   Showering and bathing create a considerable amount of steam in a short space of time, so condensation is inevitable. Opening the window will allow the steam to escape quickly. The wider it is opened, the better. It may be necessary to keep the window open for some time after, too, to ensure all the moist air has escaped. And close the internal bathroom door to prevent steam from escaping into the home instead.
    

4. Open windows in kitchens when cooking
   Cooking, boiling pans and using the kettle create a lot of steam in a kitchen. As do activities such as washing up, clothes washing and using a tumble dryer. Opening windows wide whilst doing these activities will provide ventilation and allow the warm air to escape rather than cause condensation on the window.
    

5. Dry clothes outside
   As they dry, wet clothes placed on an airer or radiator release moisture into the air, raising the humidity and causing condensation. Preferably, clothes should be dried outside. But if that’s not possible due to the weather, open windows to allow the air to escape. Also, try to dry clothes in a room with plenty of windows to allow sunlight to dry them quicker.
    

6. Keep heating on constantly at a low temperature
   Extreme and frequent rises and drops in temperature exacerbate condensation problems. First, the decrease in temperature when the heating goes off makes windows cold. Then the sudden rise when the heating comes on warms the air quickly, but not the glass, so condensation forms. Keeping the heating on constantly but at a lower temperature stops the glass from getting as cold and helps to prevent condensation from forming.
    

7. Replace windows with condensation between the panes
   Double-glazed windows will never have condensation trapped between the two panes of glass unless they are faulty. If this happens, then the windows will need to be replaced.
    

8. Fix damp problems
   Excessive condensation can cause damp, but not all damp is caused by condensation. Damp can also be caused by structural problems, which we cover in more detail later in this guide. Damp increases humidity and therefore increases the chance of condensation forming on windows. So, fixing the damp problem will also stop condensation on windows.

Condensation doesn’t just affect windows. It will form on any cold surface, including walls. And if the wall is left damp for too long, mould can grow, so it must be removed as quickly as possible.

Use one of these three methods to remove moisture from walls:

1. Ventilate the room daily to allow moisture to evaporate by opening the windows wide for 20 minutes

2. Use a dehumidifier to draw out and capture the moisture

3. Use anti-condensation paint on the walls to add an extra layer of insulation and prevent condensation from building up

Condensation in the home can be stopped by reducing humidity and increasing ventilation. Less humidity in the air means less water vapour to turn into condensation. And increased ventilation provides a way for water in the air to escape.

Damp surfaces provide ideal conditions for mould and mildew to grow, and mould can cause serious health problems. So, it’s vital to get rid of mould and stop it from coming back. 

To stop mould:

1. Prevent walls from getting damp by opening windows or turning on an extractor fan when showering or bathing

2. Dry damp walls using a towel within 24 hours to prevent mould from growing

3. Clean, disinfect and dry surfaces prone to mould growth

To stop mould from coming back, you must remove all traces of mould growth and spores that linger in the air:

• Remove mould by washing it away with ready to use mould and mildew spray or a mix of one part bleach to four parts water

• Dry all surfaces after washing

• Disinfect wooden surfaces

• Replace cardboard storage boxes to get rid of any remaining mould spores

• Throw away soft items that are mouldy and can’t be washed

• Shampoo soft furnishings

• Vacuum 

Condensation is one of the most common causes of damp in a home. But it’s not the only cause. Damp can also be caused by structural problems such as penetrating rain on an exposed wall, failed damp-proof course, overflowing gutters, a leaking roof, and plumbing problems.

Signs of damp in a home are damp patches on walls, flaking plaster, peeling wallpaper and mould growth. You may also notice a distinct, musty, damp smell. Here’s our advice to remove this odour. 

Discover how to get rid of that damp smell:

• Ensure all traces of mould and mildew are washed away (as described in the section above)

• Try washing musty smelling soft furnishings in the washing machine with some white vinegar added to the usual detergent 

• Throw away items affected by mould if they can’t be cleaned

• Get the air circulating in the home – open windows and use fans to blow fresh air through and stale air out

• Put some charcoal or cat litter in a jar next to an area affected by damp to soak up the damp smell

• Boil some lemons, then leave them in the musty smelling room to cool off 

Once you’ve got rid of the musty smell, stop it from coming back by getting rid of all damp. 

1. Regularly clear condensation from windows with a towel or window vac

2. Use a dehumidifier to draw out and capture moisture

3. Open windows for 20 minutes every day

4. Increase ventilation (see the air ventilation improvements section below)

5. Keep the house warm, so surfaces don’t get cold and attract condensation

A dehumidifier is an air conditioning unit that removes humidity from the air to prevent the build-up of condensation and damp.

There are two types of dehumidifiers:

• Refrigerant dehumidifier
  A refrigerant dehumidifier works by drawing air through a filter and over cold coils. Water condenses on the coils and drips into a water tank. This type of dehumidifier needs the air to be warm to work, so it’s best suited for use in heated rooms.
• Desiccant dehumidifier
   A desiccant dehumidifier extracts water from the air using an absorbent material. The material is heated to turn the moist air into water, which then drips into a water tank. This type of dehumidifier is best suited to cold, unheated rooms.
• Are dehumidifiers good for damp?
  Dehumidifiers vastly improve damp and condensation problems in a home because they reduce moisture levels. They’re most useful in rooms where there’s a lot of humidity. For example, a kitchen or bathroom. A room where clothes are dried. Or in a bedroom where condensation builds up from the heat caused by breathing. 
  Watch our video to see how the WDH 16L dehumidifier works:
  https://www.youtube.com/watch?v=DMopw45GbiQ 

Removing condensation as quickly as possible is a good way to reduce the risk of damp and mould forming. But it’s better to prevent condensation in the first place. And the best way to do this is by using products designed to improve ventilation as follows:

• Ventilation building materials
  Ventilation building materials are devices that are installed into walls, windows or roofs. They improve ventilation by allowing air to flow through them in both directions so the building can breathe and moisture can escape. Several types of ventilation building materials are available, such as air bricks, air vents, roof ventilation tiles, ventilated soffits and window vents.
• Heating and insulationThe frequent rises and drops in temperature caused by central heating being switched on and off contribute to condensation forming. This is further exacerbated in a home with poor insulation because the temperature difference is more dramatic. Also, the colder a surface is, the more likely it is that condensation will form on it. Improving insulation adds overall warmth to a home and prevents extreme temperature changes. It also helps to keep surfaces warmer. So, cavity wall insulation, for example, stops cold spots on walls. And loft insulation prevents the ceiling from being cold.
• Bathroom ventilation
  Bathrooms are the most humid rooms in a home. One of the simplest ways to reduce condensation is to open a window when showering or bathing. But this doesn’t stop condensation entirely and isn’t practical during the winter. So, to increase ventilation, install an extractor fan. For best results, leave the fan running for an hour after the shower or bath, and close the internal bathroom door to prevent moisture from escaping into the home.
• Kitchen ventilation
  Kitchens are also humid rooms due to the steam created when cooking. Open the windows when cooking to allow steam to escape to improve ventilation. You can also install an extractor fan above the hob or stove which will draw the moisture out of the air as it’s created. Keeping the lids on saucepans also helps to reduce the steam escaping so much. And if there is a vented tumble dryer in the kitchen, ensure it’s adequately vented to the outside.

If damp and mould caused by condensation become a big problem, it’s worth investing in some long-term solutions to stop it from coming back.

Long-term solutions include improving ventilation and insulation, as described in the section above. Upgrading single-glazed windows to double-glazing. And installing extractor fans in the kitchen and bathroom.