WORKING TOWARDS A SUSTAINABLE COMMUNITY

Humidity, Condensation & Mould
The Barrow Greener Living booklet, Save Energy-Save Money, and our Heat Loss Surveys often recommend preventing cold draughts as a means of reducing energy consumption to keep homes warmer. However, it’s important to note that if you block too much ventilation to make it warmer, humidity levels are likely to increase with the potential for increased condensation and mould growth. Before energy prices rocketed, most people could afford to heat their homes and did not worry so much about draughts meaning there was sufficient ventilation and warmth to keep humidity under control but now the issue of condensation and mould should be considered as part of making homes more energy efficient.

What is humidity?
Humidity is a measure of water that is contained in the air. Usually, humidity in the home is between 50% and 60-70%. At higher levels, dependent upon room temperature, it can be a problem as it can lead to condensation, damp and the formation of mould.

What produces excess humidity?
Many different things can produce higher humidity: 1) people breathing – a family of four adds about half a pint of water to the air every hour; 2) cooking one meal a day can add 2 pints; 3) showers contribute a half-pint; 4) any activity that uses water (like dishwashing, mopping floors, laundry) adds moisture to the air; 5) drying clothes on radiators causes high levels of humidity. To summarise, daily living activities for a family of four, in just one week, can add more than 18 gallons of water into the air. That’s a lot of water!

Humidity can cause condensation.
Condensation is the change of water vapour into liquid water. It usually happens when warm air that's full of water vapour (higher levels of humidity) comes into contact with cooler surfaces such as a window or an external wall. When the air cools, it can't hold as much water vapour, which causes it to change into tiny droplets of liquid. Condensation is the most common cause of damp which can then result in mould.

Condensation can lead to mould.
Mould is a form of fungus and can develop on any cold, damp surface but also curtains, behind wallpaper, carpets, upholstery and more rarely, under floorboards or on attic timbers. Particularly, where there is poor circulation of air. Check for darkish damp areas, with black spots or even water-filled blisters on outside paint surfaces.

Preventing condensation will help to prevent mould.
1. Monitor humidity
 • Humidity monitors are cheap to buy – every home should have one. Higher humidity levels (measured in %) are more likely to produce condensation, leading to problems with  damp and mould.
 • Use a humidity monitor to find out which rooms need to be ventilated more frequently.
2. Reduce moisture in the atmosphere
 • Turn on the kitchen fan when cooking and keep lids on pans.
 • Keep bathroom and kitchen doors closed when showering or cooking.
 • If possible, avoid drying laundry inside and use the washing machine spin cycle twice. Use a tumble dryer or hang damp washing in a room with the internal door closed and a window open.
 • Make sure clothes are completely dry before putting them in a wardrobe or drawer. • Wipe down surfaces where you see condensation collecting and after a shower.
3. Controlled ventilation
 • If humidity is a problem, open doors and windows if appropriate.
 • Open kitchen and bathroom windows to allow steam created by cooking, showering or bathing to escape.
 • When you bathe or shower, turn on the fan until the mirror is clear.
 • If there is no fan in the bath or shower room keep the room door shut but open a window to let moist air escape.
 • Vent all clothes dryers and exhaust fans to the outside.
 • If high humidity is noticed, make sure that trickle vents on windows are open and airbricks are not blocked. If the vent has a cover, move it to the open position.
 • If you notice mould behind sofas or other furniture, move them away from the wall to allow air to circulate.
 • If there are lots of people or pets in a small space, you will most likely need to increase ventilation.
4. Ensuring a warmer home
 • Warm air holds more water vapour so make sure your heating system is working efficiently.
 • During colder times of year, turn your heating on regularly. This doesn’t mean all day but often enough to keep humidity below 65%.

5. Use a dehumidifier
  Dehumidifiers take moisture out of the air especially if you have followed all the actions previously mentioned but humidity remains high.
 • Set your dehumidifier to under 60% if possible. • On warm     days opening a window is just as effective as running a dehumidifier.
 • Close doors and windows in the room where the dehumidifier is on; it will work more efficiently.
 • Buy a dehumidifier that will remove at least five litres of water every 24 hours. Avoid smaller, cheaper models. Decent dehumidifiers start at around £100 and cost around 17p per hour to run (based  on a price for electricity of 27p per kWh, November 2023).

This article is a brief introduction to the topic but there is more detailed information called “Air Quality” on the Barrow upon Soar website in Community – > Community Groups – > Barrow Greener Living Air Quality.pdf (barrowuponsoar.org.uk)

Barrow Greener Living Group