What is Condensation?
Here is a useful guide to condensation from Manchester Student Homes: Condensation Guide (MSH)
Condensation occurs where moist warm air comes into contact with colder dryer air, or a surface, which is at a lower temperature. Air contains water vapour in varying quantities; its capacity to do so is related to its temperature – warm air holds more moisture than cold air. When moist air comes into contact with either colder air or a colder surface, the air is unable to retain the same amount of moisture and the water is released to form condensation in the air or on the surface. Condensation is generally noticeable where it forms on non-absorbent surfaces (i.e. windows, window sills, mirrors or tiles) but it can form on any surface and it may not be noticed until mould growth or rotting of material occurs.
Condensation on windows, windowsills and ceramic toilet cisterns is completely normal and expected.
Conditions for Condensation
In Britain condensation in houses is mainly a winter problem, particularly where warm moist air is generated in areas like kitchens and bathrooms and then penetrates to colder parts of a building. The moisture in the air comes from a number of sources within the house. Water vapour is produced in relatively large quantities from normal day to day activities – a 5 person household puts about 10 kg of water into the air every day (without taking into account any heating). For Example (1 kg of water equates to about 1 litre):
- breathing (asleep) 0.3 kg
- breathing (awake) 0.85 kg
- cooking 3 kg
- personal washing 1.0 kg
- washing and drying clothes 5.5 kg
- moisture can also be drawn from the structure of the building into the internal air, from below the floor or through the walls/ceilings.
Ventilation and Insulation
Keeping the moist air in the house through effective draught-proofing aggravates the effect of moisture generation. It is possible to avoid condensation altogether by adequately venting moist air from the room in which it is generated. In certain areas of a house (such as bathrooms and kitchens) the warm air contains a lot of moisture; if that air then spreads to cooler parts of the house it condenses on any colder surface.
Up until the middle/late part of the twentieth century most houses had high natural ventilation, as the level of home insulation was low, draught proofing was non-existent and open fireplaces and chimneys allowed air circulation. As Energy Conservation became necessary, natural ventilation was greatly reduced by the introduction of double glazing, draught excluders, fitted carpets (which prevent air movement up through suspended wooden floors) and, with the introduction of central heating, the removal of open fireplaces. Houses have become effectively sealed boxes, keeping in any moisture produced within the house and providing ideal conditions for condensation to occur.
Ventilation is only effective if it is consistent throughout the whole envelope of the house. Condensation is encouraged by poor air circulation where stagnant air pockets form (behind furniture and in cupboards) and the first evidence is often the appearance of mould growth and a musty smell on clothes in wardrobes. The warm moist air rises to the highest points in the building, forming condensation in those areas, which are often oldest, including bedrooms, wardrobes and upstairs bathrooms and toilets etc.
Lifestyle Causes
The modern lifestyle and particularly that of student tenants, means that many houses remain unoccupied and unheated throughout the greater part of the day, allowing the fabric of the building to cool right down. Cold walls and masonry hold more moisture which adds to the cooling effect, creating a vicious circle—cold walls, more moisture, colder, damper walls. The moisture producing activities are then concentrated into a relatively short time period in the evenings, producing large amounts of steam when the building structure is still relatively cold. Although there are other causes, by far the most common cause of mould growth in a rental property is condensation. Very often the main cause of condensation resulting in mould growth is the lifestyle of the occupants – the tenants themselves: Lack of heating in an attempt to economise, lack of venting of steam-generating activities result in condensation and long-term, in mould and fungus growth.
First steps against condensation and mould growth
Here are some basic steps you should do straight away to avoid condensation and ould growth:
- If you already have mould growth, the Landlord will only be able to treat the area and paint over it once it has dried.
- Dry your windows and window sills every morning as well as surfaces in the kitchen or bathroom, which have become wet. Wring out the cloth – don’t dry it on a radiator.
- Help reduce condensation, which has built overnight by “cross ventilating” the house. Open a small window downstairs to the first notch and the same to a small window upstairs. They should be opposite sides to the house or diagonally opposite if you live in a flat. At the same time open the internal room doors – this will allow air to circulate throughout the house. This type of cross ventilation should be carried out for about 30 minutes every day if possible. But make sure those accessible windows will not cause a security problem and remember to close them before you go out.
- Ventilate the kitchen when cooking or washing. A window slightly open is as good as one fully open in these situations. If you have one, use the cooker extractor hood or extractor fan.
- Avoid drying clothes on radiators.
- Always cook with pan lids on, and turn the heat down once the water has boiled.
- When filling your bath, run the cold water first then add the hot. This will reduce the steam, which leads to condensation, very significantly (up to 90%).
- Keep kitchen and bathroom doors closed when you are using these rooms to prevent moisture escaping into the rest of the house.
- Ventilate your bathroom and kitchen for about 10 to 20 minutes after use by opening a small top window. Use an extractor fan if fitted – they are very cheap to run and very effective.
- Ventilate your bedroom by leaving a window slightly open at night or use trickle ventilators if fitted. But again remember the security.
- Do not draught-proof rooms with a condensation problem or where there is a heater or cooker that burns gas or solid fuel.
- Do not draught proof bathroom or kitchen windows, as this will prevent some natural, helpful ventilation.
- Do not block ventilators or airbricks for the same reason.
- Always try and keep some background heating on in the house to maintain warmer surfaces and help control condensation.
- If you don’t have heating in every room, keep the doors of unheated rooms open to allow some heat into them.
- Mould growth on clothes or other stored items is very difficult to prevent because it is necessary to provide good air movement in wardrobes and cupboards. The following hints should prove helpful:-
- Keep a small gap between large pieces of furniture and the walls.
- Where possible place wardrobes and furniture against internal walls.
- Try to avoid overfilling wardrobes and cupboards, as this will restrict air circulation.
ALWAYS USE EXTRACTOR FANS WHERE PROVIDED AND DO NOT CLOSE WINDOW VENTS.