The causes and consequences of condensation
Condensation forms when warm, moist air meets cooler surfaces, leading to water droplets accumulating
Condensation is a common occurrence in many homes. It forms when warm, moist air produced by everyday tasks – such as cooking, showering and drying clothes – can’t escape from a room and reaches a cold surface. The difference in temperature causes the warm air to condense into water droplets that collect on these cold surfaces, commonly windows and walls.
If these water droplets aren’t wiped away, tiny mould spores in the air can land on the moist surface and begin to grow as mildew, also known as ‘surface mould’.
There are three main causes of condensation in a property:
The room temperature is too cold, meaning any warm air created is likely to condense
There is a lack of ventilation in an area of high steam production, such as kitchens and bathrooms
The property generally has an excess of moisture-rich air – for instance, due to the number of occupants or because a lot of washing is being left out to dry
Lack of insulation at construction – older buildings may not be well enough insulated, meaning the interior walls may be colder and more susceptible to condensation
Cold spots/bridging – some materials used during construction are naturally colder than others, such as concrete beams, which can be difficult to insulate adequately
Colder weather – condensation is more common during cold weather and is more likely to collect in areas where there’s not much air circulation, such as behind furniture
Preventing condensation in rented properties relies on the efforts of both landlords and tenants. Landlords have to make sure that the property remains in good condition with all the fittings and services working properly, and the tenants need to do their part to be considerate while living there.
For example, if an extractor fan is poorly fitted and not working well enough to remove steam from a bathroom, that’s a failing on the landlord’s part. But if condensation is causing surface mould to form in bedrooms because tenants are drying washing in there and not opening the windows, they could be causing the problem.
Although it’s down to you as the landlord to fix all damp and mould problems if they do occur, if you are able to prove that the tenant either directly caused the issue or made it worse through not reporting it early, you may be able to reclaim some of the cost of repairs from their deposit at the end of the tenancy.
Tenants should be encouraged to always report any issues they find at any point during the tenancy, to give the landlord an opportunity to investigate and address the problem at the time, and to avoid it getting worse. It is important to do this in writing so there is an audit trail if it does, at any point, become an issue.
See our deposit protection partner, mydeposits, separate article on understanding damp, mould and condensation: how to avoid deposit issues, for more information and read mydeposits case study on damp and mould here.
Nevertheless, it should be possible to avoid most condensation issues by reminding tenants of the simple steps they can take.
We’ve put together a tenant checklist for you to share with your tenants to help them recognise what type of damp or mould you might have, what you can and should do about it, and how they can prevent it.
Download a printable version to share with your tenants here
As the landlord, two key steps for you to take are:
Make sure your rental is properly insulated – see our guide to having an energy efficient, eco friendly property for detailed information and advice
Make sure that the property can be well ventilated, with trickle vents in double-glazed windows and efficient extractor fans in areas where a lot of moisture and steam tends to be produced, such as the kitchen or bathroom
Then we’d recommend you pass on the following tips to your tenants:
Always use extractor fans where they are provided and report any problems with them right away
Air the property as much as possible by opening windows, when safe and suitable to do so – even if it’s just for a short time every day
Close off any moisture or steam in a room to stop it spreading through the property, for example by keeping the bathroom door shut during and after a bath or shower. Having a bath produces around two pints of moisture, a proportion of which could be circulating around the house!
Avoid drying wet clothes on radiators and keep the space around them clear so the warm air can circulate properly
Make sure any room used for hanging out laundry is well ventilated
If condensation does collect on window sills or other surfaces, wipe it away to prevent mould forming
Keep the thermostat at a minimum of 15°C in very cold weather – not only will this help reduce condensation levels in the property, but it will protect the pipework from freezing
And emphasise to your tenants the importance of letting the property manager know as soon as any problems arise, so they don’t become long-term issues.
If you (or your managing agent) are notified about a condensation or mildew problem, address it right away and confirm the action and timeline required to deal with the problem in writing.
Not only will this make sure it doesn’t develop into more serious mould growth, but your tenants should appreciate you being responsive and may be encouraged to be more careful about ventilation and cleaning in future.
