What is Condensation?
Time for a science lesson!
The air all around us contains moisture. Teeny tiny droplets of water hanging in the air, so small we can’t normally see or feel them. The warmer the air temperature, the more moisture the air can contain, and the colder the air temperature, the less moisture it can hold. When warm air full of moisture comes into contact with a cold surface, the moisture vapour reverts back into a liquid. We can see this as water droplets forming on surfaces – the most common being window glazing, tiles, mirrors and even walls. It can even form inside the construction materials themselves.
The temperature that condensation forms at is known as the ‘dew point’, and this changes with the relative humidity. This is basically the amount of water vapour that’s present in the air, expressed as a % of the amount needed to achieve total saturation at the same temperature.
For example, say at an air temperature of 20°C with a high relative humidity of 85% the dew point may be around 17°C, condensation could therefore form on any surface below 17°C, which could be quite likely given the small difference in temperatures. However, at the same temperature of 20°C and a lower relative humidity of 55%, the dew point would be around 10-11°C, so condensation would form on surfaces with a much lower temperature. All that to say that dew points aren’t static, and will change depending on the air temperature and the amount of water vapour in the air.
What Affects it, and Why is it a Problem?
On top of the normal moisture present in the air, it’s released into the air through normal activities like breathing, bathing, cooking and drying clothes indoors. For reference, the average family produces 12-15 litres of water per day this way, just through normal day-to-day activities.
The more people in the building doing all of these things, the more moisture vapour is created. If the building isn’t properly heated or ventilated, there’s a much higher chance of condensation forming on any surface below the dew point.
If the building suffers from repeated or persistent condensation for a long time, it provides the perfect breeding ground for mould spores. These spores are always in the air around us, but need that wet environment to germinate. Mould is a pretty nasty problem to have, causing damage to decorative finishes and soft furnishings as well as increasing the risk of asthma and respiratory illness. And the longer it’s left, the worse it gets.
What can I do?
The key to managing condensation is to keep the fabric of the building above the thermal dew point. This can be done by maintaining a reasonable balance between heating and ventilation, and having good quality humidity-controlled extraction ventilation in kitchens and bathrooms. If you have to dry clothes inside, you should invest in a dehumidifier to reduce the moisture, but this will only tackle the moisture and not other causes of condensation.
A few other things you can do to reduce the amount of moisture in the air include:
• Keep the lids on pans when cooking and only use as much water as necessary.
• When you’re running baths, put cold water in first and then top it up with hot to produce less steam.
• Try to avoid drying clothes indoors or on radiators. Use a dehumidifier or extract ventilation if you have to.
• Install or use extractor fans in kitchens and bathrooms. Continuous running or humidity-controlled fans are best for this.
• Ventilate your property properly. Keep window trickle ventilators open or open windows on opposite sides of the house in the morning for a short period. Not for too long though – you don’t want the internal temperature of the house to drop too much!
Mould and condensation tend to form in areas where there’s reduced air circulation and lower temperatures. So little things like not overfilling built-in cupboards and leaving space between walls and furniture can be a huge help. Making sure your property is insulated adequately can be a huge help too.
Use the heating to maintain a low background temperature that’s warm enough to prevent condensation, including in unoccupied rooms. You can use the thermostatic control valves on your radiators for this. We know this is difficult, especially with rising energy costs, but it’s a lot cheaper than the cost of dealing with mould!
What if I Still Have Problems?
If you’ve done all of that and you’re still having mould and condensation problems, it’s time to dig a little deeper. A lot of people would say it’s the fault of the people in the building at this stage, but we know better. There may well be underlying issues with the building construction, or defects that can cause moisture levels to increase or facilitate condensation forming. These might include:
• Properties that are difficult to ventilate of heat because of their position or construction.
• Damp ingress from external sources, leaking pipes or wet insulation, all of which might lower the surface temperature of your walls.
So if you’ve tried everything, it’s time to investigate the property itself. At Harrison Clarke we have an experienced team of surveyors who can assess properties and provide advice for damp and condensation. If you need expert advice for your property, just get in touch with our team on 023 8155 0051, and we would be happy to help.
For more expert advice on surveying and property matters, check out our range of informative videos on our website or YouTube channel. Harrison Clark Chartered Surveyors is here to guide you every step of the way!
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