How can I prevent condensation on the insides of my windows?


Condensation on the insides of your windows is a common occurrence once the weather starts getting colder. From autumn through winter and into the beginnings of spring, the chilly weather causes condensation which may lead to problems with your home and your health if not dealt with.

A little condensation may not be much of an issue, but a lot of condensed water continually building up on your windows will cause problems over time. This article details the causes of condensation, as well as tips on how to prevent it.



Why does condensation occur?

Frost on window

The cold days and even colder nights in the autumn and winter months make the glass in your windows very cold to the touch.

In contrast to this, the inside of your home will be warm, keeping you and your family toasty. Warm air is better able to hold moisture, so once this air begins to cool it cannot hold the moisture any longer and it turns into droplets of water.

The natural water vapour in the air, added to by breathing, cooking, showering and other daily household activities, condenses when it comes into contact with the cold surface of the window pane. This causes droplets of moisture on the glass. In particularly bad cases, the condensation present may be sufficient to result in water running down the window pane.



What causes condensation on the insides of windows?

Cooking steam

Modern life has led to an increase in water vapour production, while the modern home means that it is harder for water vapour to escape.

There are many everyday activities which add to the natural humidity of the air, including breathing, cooking and washing.

Take a look at the amount of water that can be released in a 24-hour period by an average family:

  • 4 people sleeping: 1.5 litres
  • 4 people active: 3.2 litres
  • Cooking: 2.6 litres
  • Washing up: 1.0 litres
  • Washing clothes: 4.0 litres
  • Drying clothes: 4.5 litres
  • Bathing: 0.5 litres

This means that a family of four can easily create 17.3 litres of water in a day. That’s 121.1 litres or 26.6 gallons per week.

While there are many advantages to the well-insulated nature of the modern home, this unfortunately makes it more difficult for water vapour to escape. Lack of ventilation is one of the main causes of condensation in the home.



How do I prevent condensation on the insides of my windows?

The main ways to prevent condensation are controlling sources of humidity, keeping your home at a constant temperature, and ensuring adequate ventilation.

Control the sources of humidity

Extraction fan

It would be ridiculous to suggest that you simply stop cooking or showering in order to reduce your home’s relative humidity, but there are many ways in which you can lessen the output of water vapour, including:

  • When cooking or showering, ensure that you use an extractor fan to pull the steam out of your home
  • Ensure that all gas burners, tumble dryers, etc. are properly vented to the outside
  • Keep the bathroom or kitchen door closed to prevent the moisture escaping to other parts of your home
  • Cover pots with lids when cooking and only use the minimum amount of water needed when boiling
  • Hang your clothes outside to dry when you can
  • Avoid using paraffin and portable flueless gas heaters, as these release a lot of moisture into the air when they burn

You might also want to try using a dehumidifier to get rid of excess moisture in the air, though these can be expensive to run and are not ideal as a long-term solution.

Keep your home at a constant temperature

boiler dials being turned

Keeping your home at an even, low temperature for prolonged periods of time is a good way to ward off condensation. This prevents areas of cold, which is where the condensation is most likely to occur. In cold weather, set your central heating to provide a constant background heat throughout the day, even when there is nobody home and in rooms which are not used.

You could also look into insulating your loft or cavity walls to better keep the heat in. Government grants and discount schemes are often available if you are unable to afford heating costs or insulation work.

Ensure adequate ventilation

Window ventilation

You should always make sure to air out your home for a few minutes every day. Outside air generally has a lower humidity than the air inside your home, so along with allowing higher humidity air to leave the property, it also allows drier air to enter. This brings down the relative humidity of the air in your home.

One of the reasons why we see more condensation in the winter is because we shut up our homes to keep them warm, which also traps the damp air inside. While it may be a bit chilly, airing out your home in the winter is important to prevent a build-up of damp.

Try opening your windows just a crack to let the house air out over a period of a few hours, or opening them wide for just a few minutes. Be careful not to over-ventilate your home during cold weather, as it will make your home colder and require that the boiler work harder to reach the desired temperature. The knock on effect then is that it'd bump up your heating bills.



Damage caused by condensation on windows

Rusty nail

A small amount of condensation just in the corners of your windows probably isn’t going to cause too many problems, but if you’re frequently seeing a lot of condensation, enough to cover a large area of your window or even causing water to run down the window pane, then you’re likely to see damage if you don’t take care of the issue.

This damage can include:

  • Damage to wallpaper, including staining, warping and peeling
  • Damage to plaster
  • Damage to paintwork
  • Rotting of wooden frames or sills
  • Rusting of metal components in or around the windows

You should bear in mind that if there is condensation on your windows which you are seeing, there could be condensation build-ups in other areas in your home that you do not see. It is possible that there could be condensation in your loft, for example, where it may be causing unnoticed damage.

If you are seeing a lot of condensation on your windows, it’s worth checking other areas of your home for condensation and any resulting damage. Glass, paint, tiles, varnish and plastics are all materials which stop water vapour ad cause condensation to form on their surface. If your home is damp, you may see rot in woodwork or plaster, which can be costly to fix.



Condensation and mould growth

Mould on window

While water vapour itself does not cause any health problems, damp conditions and high humidity often lead to mould growth. In large quantities, mould spores can be really bad for your health. Mould can be detected by the appearance of patches and spots on surfaces, along with a musty odour. It can also damage, stain and ruin anything from paint and wallpaper to clothes and furnishings, which could be costly to replace if left untreated.

The most common mould caused by condensation is black spot mould, although other types of mould may occur depending on conditions. Some types of mould are toxic, such as Stachybotrys chartarum, which is black and slimy, so you should always be careful when investigating mould growths.

Mould requires a persistently high humidity in order to thrive, usually over 75%, and, as such, it usually develops in areas with poor airflow and high levels of damp. This makes bathrooms a very common area for mould growth.

The health problems most associated with mould include respiratory problems, asthma and allergic reactions. It can also affect the immune system, making you more susceptible to viruses and infections. If you are unfortunate enough to be harbouring toxic black mould, the health concerns are more serious, and can include neurological, circulatory and even vision problems. If you are experiencing severe mould problems, you should seek professional advice for removal and treatment.


VHL in London

If you’re looking for the most efficient way to heat your home and keep condensation at bay, speak to VHL’s expert team. We will work with you to determine the perfect boiler solution for your home, so get in touch today.


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