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Under the skin of the letting market

Here we share news and views on both the local letting market in & around Oxfordshire and all planned and recent legislation.

The invisible source of an unsightly problem


Condensation is a real issue between October and April in Oxford as the external air temperature falls and water from the air forms as condensation on cold surfaces such as windows and external walls. Everyone has heard the horror stories of bathrooms and kitchens with blackened ceilings and window sills, but explaining to tenants that the cause is most probably due to their lifestyle isn’t always a nice or easy conversation.

The biggest hurdle is in explaining something invisible to someone. Water in the air from cooking, washing and showering is clearly visible as steam but there is also much more water in the air that you cannot see, especially in areas where the water table is fairly close to the ground (as it is in Oxford) rather than buried many metres below it. This ‘invisible’ water content is just waiting to condense on a cold window or north-facing wall.

This year we took a different approach to condensation because we wanted to help tenants to take control and so we invested in some Humidistats. These handheld machines show the humidity readings in a given room as a percentage. It is widely accepted that mould will not grow in rooms where the humidity is kept below 50%, and it would appear that 50% – 55% is the tipping point.

The tabletop Humidistat shows the levels of humidity in a room

We have had some excellent results with this system. Earlier this year some tenants of a 3-bedroom house reported mould on the wall in their kitchen and in the first floor front bedroom. They were very unhappy and demanded that the landlord fix the problem immediately. We visited the property and took a reading in the kitchen of 56% humidity and a further reading taken in the bedroom measured 62% humidity.

The tenants were advised on correct ventilation and heating, and asked to open windows and use the extractor fan to remove excess moisture when cooking. One of the tenants was also using a small fan heater in her room; she was asked to turn the fan heater off and open the window for at least half an hour every day for the next seven days.

We left the tenants with a dehumidifier and a small tabletop Humidistat so that they could monitor and control the humidity levels. A second inspection one week later revealed that the humidity in the kitchen had reduced to 43% and the reading in the bedroom had reduced to 46% – a dramatic decrease!

The tenants were very pleased with the results and recognised that their own day-to-day habits had been causing the problem. They were happy to continue to control the humidity levels themselves in future and even commented that the house felt warmer, which is because it is easier to heat dry air rather than wet air.

These miniature weather stations have helped to educate tenants as they clearly illustrate that open windows and a more moderate temperature causes the humidity to drop and the problem goes away.

How can I stop condensation?

  • Open your windows! Even keeping a small window open will make a big difference
  • Use and maintain extractor fans in kitchens and bathrooms and keep doors closed
  • Dry your washing outside if you have outside space. Open a window if drying washing indoors and use a tumble dryer where you have one
  • Ventilate cupboards and wardrobes – do not overfill. Let the air circulate freely
  • Wipe water from windows and sills where condensation has gathered
  • Draw back curtains in all rooms every day to avoid staining the linings