Waking up to wet windows on a cold morning is something many UK homeowners will be familiar with. You might notice droplets running down the glass, damp window sills or patches of moisture appearing on colder walls. This is condensation.
A small amount from time to time is rarely cause for alarm. However, frequent condensation can create the damp conditions that encourage mould growth and damage decorations, timber and other materials around your property.
If you have found yourself wondering, ‘why does condensation happen in my house?’, the answer usually comes down to a combination of moisture, temperature and ventilation. Understanding the problem is the first step to addressing it. In this blog, we look at what causes condensation and how to stop it.
Warm air can hold more moisture than cold air. As the temperature of that air falls, there comes a point when it can no longer hold all the water vapour it contains. This temperature is known as the dew point.
When warm indoor air meets something colder, such as a window, external wall or poorly insulated corner, the air around that surface can fall below its dew point. The excess moisture then turns into visible water droplets.
Think about the steam that appears on a bathroom mirror after a hot shower. The mirror has not suddenly become wet because water has entered through the wall. Warm, humid air has simply reached the colder glass and condensed. The same process can happen throughout your home.
Condensation can occur at any time of year, but it tends to become much more noticeable during autumn and winter. Firstly, the surfaces around your home become colder. Windows, external walls and poorly insulated areas are much more likely to reach temperatures where condensation can form.
Secondly, we naturally ventilate our homes less when it is cold outside. Windows stay closed, doors are kept shut and heating is switched on. This can leave the moisture produced during everyday life trapped inside the property. The result is warm, humid indoor air meeting increasingly cold surfaces.
That is why you may see little condensation during summer, only for wet windows and damp corners to appear once temperatures begin to drop.
Moisture is constantly being produced inside an occupied home. In most properties, this moisture causes few problems as long as there is enough ventilation for it to escape.
Problems can start when more moisture is being produced than the property can remove.
Common sources of indoor moisture include:
Even something as ordinary as preparing dinner or hanging washing on a radiator can increase indoor moisture.
One activity on its own is unlikely to cause a serious condensation problem. When several sources of moisture combine with limited ventilation and cold surfaces, however, humidity levels can quickly rise.
Windows are often the first place condensation becomes noticeable because glass tends to be one of the coldest surfaces in a room.
Older single-glazed windows can be particularly prone to the problem, although condensation can also appear on double glazing, especially during very cold weather or when indoor humidity is high.
You may notice condensation first thing in the morning in bedrooms. During the night, people continue to release moisture into the air through breathing while doors and windows are generally closed. As outdoor temperatures drop, the glass becomes colder and water begins forming on the inside.
Occasional misting may simply mean the room needs better airflow. If windows are regularly covered in water or the surrounding frames and walls remain damp, it is worth investigating further.
Windows are easy to spot, but condensation does not always appear somewhere obvious.
It can develop on:
Areas behind furniture are particularly vulnerable because air cannot circulate freely. You may therefore notice black marks behind a wardrobe or chest of drawers even when the rest of the wall appears perfectly dry.
Persistent condensation can create ideal conditions for mould. Mould thrives where there is moisture and limited airflow, which is why black mould commonly develops around windows, bathroom ceilings, colder external walls and behind furniture.
Simply wiping the mould away may improve its appearance, but it will often return if the underlying moisture problem remains. Reducing the amount of indoor moisture and improving ventilation is therefore an important part of reducing the black mould risk.
If mould continues returning despite changing how the property is heated and ventilated, there may be a wider damp or ventilation problem that requires investigation.
You do not necessarily need major building work to start improving condensation. A few changes to everyday habits can make a noticeable difference.
Bathrooms and kitchens are two of the biggest sources of moisture in most homes. Use extractor fans whenever you shower, bathe or cook, and leave them running long enough to clear the humid air afterwards.
If an existing fan does not appear to be removing moisture effectively, it may need cleaning, repairing or upgrading.
Many modern windows have trickle vents designed to provide a small but continuous amount of ventilation without requiring the window to be fully opened. It can be tempting to close them during winter to keep cold air out, but doing so can reduce airflow and allow moisture to accumulate.
Check that vents are open and have not become blocked by dust, paint or decorating work.
Opening a window for a short period after activities that generate large amounts of moisture can help humid air escape before it spreads around the rest of your home. Where possible, keep bathroom and kitchen doors closed while showering or cooking so that moisture is contained until it can be extracted.
Putting lids on saucepans helps reduce the amount of steam released into your kitchen. It is a small change, but combined with effective extraction and ventilation, it can help lower the amount of moisture entering the indoor air.
A load of wet washing contains a significant amount of water, and that moisture has to go somewhere as the clothes dry. Dry washing outdoors whenever conditions allow. If you need to dry clothes inside, choose a ventilated room, keep the door closed and use an extractor fan or dehumidifier where appropriate. Avoid placing wet washing directly over radiators if you can.
Try not to push large wardrobes, sofas or cupboards tightly against cold external walls. Leaving a small gap allows air to circulate and can reduce the chance of moisture collecting unnoticed behind furniture.
Allowing rooms and surfaces to become extremely cold can increase the likelihood of condensation. Maintaining a reasonably consistent indoor temperature can help keep internal surfaces warmer, although heating should always be used alongside ventilation rather than as a replacement for it.
A dehumidifier can help reduce humidity levels by removing moisture from the air. They can be particularly useful when drying laundry indoors or in rooms where ventilation is difficult.
However, a dehumidifier does not necessarily solve the reason moisture is building up in the first place. If condensation is caused by inadequate ventilation, consistently cold surfaces or another property issue, treating the underlying cause will usually provide a more effective long-term solution.
Sometimes opening windows and using extractor fans simply is not enough. Properties with persistent condensation may benefit from improvements to their ventilation systems, particularly where natural airflow is limited or the building has become more airtight following renovation or energy-efficiency upgrades.
The right solution will depend on the property itself. Rather than installing equipment without understanding the problem, it is important to establish where the moisture is coming from and why it is unable to escape.
A little condensation on a particularly cold morning does not automatically mean your home has a serious damp problem.
You should pay closer attention if:
It is also important to remember that not every damp patch is caused by condensation.
Penetrating damp, rising damp, plumbing leaks and other moisture problems can sometimes produce similar symptoms. Correctly identifying the source prevents time and money being spent treating the wrong problem.
Condensation is extremely common in UK homes, particularly once colder weather arrives. In many cases, small changes such as using extractor fans, keeping trickle vents open, reducing indoor moisture and improving airflow can make a significant difference.
At Croft Preservation, our experienced team can assess condensation and ventilation problems and help identify the most appropriate solution for your home. Find out more about our ventilation & condensation services by contacting us on 01202 737739 to arrange expert advice. Alternatively, complete our contact form, and we’ll be in touch.
