As the temperature outside drops, how to stop condensation from affecting your windows should become a priority if you want to avoid it damaging your window frames, walls and any other areas it may be affecting.
So what causes window condensation? Basically, air contains moisture, but the temperature of the air determines how much moisture it can hold, and warm air contains more moisture than cold air.
When warm, moist air comes into contact with either a surface or air that is colder than it is, the warm air is unable to retain the same amount of moisture as it did and the water is released either into the cold air or onto the colder surface, causing condensation to form, quickly followed by mould.
The key to stopping condensation lies in controlling humidity, improving ventilation and ensuring your home is well insulated.
In this guide we explain everything you need to know about what causes condensation and your best options for rectifying the issue — and preventing it from reoccuring in the future.
What causes condensation in the home?
Day-to-day activities such as cooking, washing and drying clothes, heating and even breathing produce water vapour. Air can only hold so much moisture in the form of an invisible vapour, no matter what temperature it is.
When the air contains more moisture than it can hold, it reaches ‘saturation point’ and when this is reached, the moisture turns back into water and condensation occurs. The temperature reached at saturation point is called the ‘dew point’.
When this happens, the air has a relative humidity of 100%. But what is normal humidity in a house? The air in the majority of homes tends to have 50-70% relative humidity. Problems occur when structural defects in a building mean the moisture content has become too high; when old houses have no damp-proof course (DPC) and when there is inadequate ventilation in the home.
Period homes often have no damp proof course, which means moisture from the soil beneath the house rises up into ground floor rooms, whilst other homes suffer from bridged DPCs or damaged guttering.
How can condensation damage your home?
While condensation is obviously not too good to look at it also causes a whole host of other problems that homeowners need to be aware of.
Problems caused by condensation include:
- Timber window frames decaying
- Water droplets on windows, obscuring the glass
- Damp walls where paint and wallpaper may peel
- Types of mould on walls, window sills, soft furnishings and more
- Risk of rotting and structural decay
- Potential health issues, especially to the young, elderly and those who suffer from respiratory issues
How do you stop condensation?
There are three basic ways to banish condensation from your home once and for all.
- Control relative humidity in your home: Fit the best bathroom extractor fans in you can find and don't forget good kitchen extraction either. Shutting the doors to these rooms whilst the extractor fans work also helps.
- Ensure there is adequate ventilation. Trickle vents in windows work well, but a more sophisticated option is a mechanical extract ventilation unit (MEV) or MVHR system. These replace the air in your home by taking the stale, damp air outside, then bring fresh air back in via a separate grille, passing it back over the heat exchanger to be warmed. It is also possible to buy central extract systems which connect all of the wet areas in your home to a central fan before discharging the stale, moist air outside.
- Consider positive input ventilation: These systems work by gently supplying fresh, filtered air into the property from a unit installed in the loft area and a distribution diffuser mounted in the ceiling. The continual supply and slight positive pressure results in the air being continually diluted, displaced and replaced to create a healthier indoor air quality.
- Upgrade your insulation: Internal walls should be kept at a temperature above the dew point of the air inside in order to prevent condensation on walls. Internal wall insulation is best when it is not an option to external insulation to your property. However, wall insulation is also linked to increasing issues with condensation in other areas. Where it may raise the temperature of the wall where the insulation is fitted, areas that remain cold, such as where the internal meets the external wall can be more susceptible to condensation.
Are there any easy ways to stop condensation?
In addition to the home improvements, there are also behavioural changes you can make that reduce condensation without making significant changes to your home.
- Using the cooker hood for ventilation when cooking in the kitchen
- Using lids for pans
- Limit significant temperature changes caused by turning your heating on and off - try to keep a consistent temperature
- Dry clothes in well ventilated spaces (outside if possible)
- Don't hang wet clothes on radiators to dry
- Ensure extractor fans are on when using a bathroom or open a window
- Leave a gap between furniture and walls to allow air to circulate from the base of walls
Should I use a dehumidifier for condensation?
Investing in a dehumidifier is a really good idea if you want to reduce condensation in your home; however, it's worth understanding how they work to get the most out of them — and you really will want to seek out the best dehumidifiers for the job as not all are created equal.
The most common type of dehumidifier used in homes are compressor dehumidifiers.
"These draw in the air over have a cold-coils system," says Chris Michael, managing director of Meaco. "They have two sets of coils, the first cools to create the condensation, which is collected into the water tank, the second warms the dry air back to just above room temperature. This helps to create the dry air needed to combat condensation, mould and damp problems."
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Natasha is Homebuilding & Renovating’s Associate Content Editor and has been a member of the team for over two decades. An experienced journalist and renovation expert, she has written for a number of homes titles. Over the years Natasha has renovated and carried out a side extension to a Victorian terrace. She is currently living in the rural Edwardian cottage she renovated and extended on a largely DIY basis, living on site for the duration of the project. She is now looking for her next project — something which is proving far harder than she thought it would be.