Condensation and mould
"The house is damp." This is perhaps the most common complaint landlords and agents receive. Have you got mould on your walls, ceilings or around your windows? If so, it is almost certainly your fault and you need to take action to prevent it. This is a long explanation, but could save you hundreds of pounds if you read, understand and act upon it.
Causes of damp
There are various sources of "damp" problems.
1. Water escaping from a water pipe, waste pipe, washing machine or the central heating system can cause damp patches to appear. Technically a leak rather than damp, these usually result in a very wet area close to (but not necessarily directly under) the source.
2. Missing roof slates, blocked gutters or blocked / damaged drain pipes can all cause rainwater to enter your home. Often insulation in the attic catches small roof leaks and tenants are not aware of a problem. However, any such fault that causes damage within the rooms results in a localised damp patch usually on the ceiling or high on the top floor wall near the ceiling.
3. Genuine damp is caused by a failure in the damp course near the ground floor level of the house. A wall can be damp without any obvious signs, but when the problem is bad a visible tidemark appears up the wall. Even at its worse, such tidemarks do not travel more than one metre above the ground floor.
Water leaking into your home from a plumbing fault, loose roof tiles or rising damp are all problems that do occur, but most "damp" reported to us is in fact condensation.
What is condensation?
There is always some moisture in the air, even though you cannot see it. If air gets cold, it cannot hold all the moisture produced by everyday activities and some of this moisture appears as tiny droplets of water, most noticeable on single glazed windows on a cold morning. This deposit of water is condensation. It can also be seen on mirrors when you have a bath or shower, and on cold surfaces such as tiles, the toilet cistern or cold walls. Condensation occurs in cold weather, even when the weather is dry. Put simply, condensation forms when hot air meets cold air.
On water proof surfaces such as windows, mirrors and tiles, damage is not usually significant. However, all cold surfaces or areas where there is little movement of air are vulnerable. Examples include the recess around windows, in room corners and inside or behind furniture, in particular larger items such as wardrobes, cupboards and beds. However, in these cases the surfaces are absorbent, the water soaks into the surface and the condensation is often not noticed until mould appears. It is worth emphasising that furniture, carpets, curtains and clothing can be affected.
Problems that can be caused by excessive condensation
So there is always some moisture in the air, the problems are caused by excessive moisture during cold weather. The clocks turn back, the leaves start to drop and the "damp" complaints start rolling in!
The deposits caused by excessive condensation can lead to mould growth on walls and furniture and mildew on clothes and other fabrics. The results can be very damaging as the following photographs show:
|Condensation mould growth on back of wardrobe where furniture was too close to an external wall.||Condensation mould on curtains.|
|Condensation mould growth in window recess where curtains were left closed too often during the day.||Condensation mould growth on exterior walls where furniture was too close to the wall.|
What causes condensation?
too much moisture being produced in your home;
cold spots; and
Each of these factors and other related points are considered in the following sections.
Moisture being produced in your home
Our everyday activities add extra moisture to the air inside our homes. Even our breathing adds some moisture which is why breathing on cold windows and mirrors causes them to fog up. The following examples give you an idea of how much water could be added to the atmosphere in your house in a day.
two people at home
a bath or shower
drying clothes indoors
cooking and using a kettle
You can appreciate how a lot of moisture is introduced into the home environment.
Obviously, we cannot expect you to stop breathing. However, there are steps you can take to reduce the amount of moisture produced. For example:
hang washing outside to dry where possible;
otherwise use one room (usually the bathroom) to dry clothes with the window open slightly and the door closed to dry clothes;
do not hang wet washing on radiators;
cook with pan lids on, and do not use excessive amounts of water;
when running a bath run cold water first then add the hot.
Ventilation of the home
Ventilation helps to reduce condensation by removing moist air from your home and replacing it with drier air from outside. Quite simply, you have to open at least one window! In fact the best way to reduce general condensation is by "cross ventilating". This means opening one window downstairs and another upstairs, preferably on opposite sides of the house, by about 5cm - 10cm for about thirty minutes. At the same time, the interior doors should be open to allow the drier air to circulate.
You should also ventilate for specific sources of intensive moisture:
ventilate your kitchen when cooking, washing up or washing by hand;
ventilate your bathroom when running a bath or shower; and
ventilate both these rooms for at least twenty minutes after significant use.
In these cases, a slightly open window is all that is required. If you have one, use your cooker extractor hood or extractor fans where fitted in the kitchen and bathroom, these are cheap to run and effective. When moisture is being generated or dispersed shortly after, the kitchen and bathroom doors should be kept closed to prevent it escaping into the rest of the house.
In addition, you should ventilate your bedroom at night by having the window open slightly or, at the very least, the trickle vents open if they are fitted. This point is so important it is worth repeating. You should ventilate your bedroom at night by having the window open slightly (even only 1cm) or, at the very least, the trickle vents open if they are fitted.
So to summarise:
ventilate your kitchen and bathroom when in use and for at least twenty minutes after significant use;
ventilate your bedroom at night by having the window open slightly; and
open a pair of windows, one window downstairs and another upstairs, by about 5cm - 10cm for about thirty minutes a day.
Having said all that, do take care not to over ventilate. Provided you are meeting these basic targets and no condensation is forming, then otherwise the windows can be shut. Otherwise you will be wasting heat, the house will get cold and, ironically, you will then actually encourage condensation rather than reduce it.
Ventilation and double glazed windows
When we advise you to open windows, you must bear in mind your security needs. For example, you cannot be expected to have a main window on a ground floor bedroom open overnight. We are all familiar with modern UPVC double glazed windows, which typically have a 16mm or even 20mm gap between the two layers of glass. Often these windows have features which help with ventilation.
Sometimes trickle vents are fitted. These are plastic strips about 30cm - 40cm long which can be opened to allow a small amount of ventilation. Frankly, if fitted, they should probably be open permanently to allow a small amount of fresh air circulation.
Many of the windows can be opened about 1cm and then locked in this position, allowing a significant amount of ventilation without affecting security.
There may be a smaller top opening section which can be left open more safely.
Incidentally, if you have these modern double glazed windows and condensation forms on the inside of these in your bedroom then this is a sign that the atmosphere is very damp and you are not taking enough steps to ventilate the house.
Closely related to the need for ventilation is the need to avoid cold spots. Always leave a gap between furniture and exterior walls to allow air to circulate. Preferably, large items of furniture should be against internal walls, otherwise leave a gap of at least 10cm between the furniture and the wall.
Also, if you have built in wardrobes and cupboards the doors should be left partly open during cold weather, especially if they are on outside walls.
During cold winter weather when there is little daylight it is tempting to leave the curtains permanently closed. This makes the window recess cold and can result in mould as shown in the second photograph above.
Temperature of your home
The basic fact is that condensation is only a problem in a home that is under-heated and under-ventilated.
Warm air holds more moisture than cooler air which is more likely to deposit droplets of condensation round your home. Heating one room to a high level and leaving other rooms cold makes condensation worse in the unheated rooms. That means that it is better to have a medium-to-low level of heat throughout the house.
Modern life styles mean that many houses remain unoccupied and unheated throughout the greater part of the day, allowing the fabric of the building to cool down. The moisture producing activities are then concentrated into relatively short periods (morning and evening) when the structure is relatively cold as the building is still warming up. However, in a student household, if you are on different timetables more often than not there is someone in the house. This means that keeping the heating on a medium temperature setting all day (say 15°C to 18°C) in cold weather will help to control condensation and give an acceptable level of comfort for all.
In fact, there is an argument that in an older house especially, it is more comfortable and no more expensive to leave the heating on a medium temperature setting (say 15°C to 18°C) 24 hours a day, compared to having a higher setting during part of the day and in the evening, then allowing the house to cool down overnight.
As condensation problems can occur away from the source of the moisture, you should not turn off the heating completely in unused rooms. If you do have an unused room, be especially careful to make sure no furniture is right up against exterior walls, leave the curtains open and make sure the radiator is on at least a low setting. The room should be checked regularly.
Cost of heating
Often students decide not to heat the house properly in an attempt to save heating costs. We have walked into houses where the occupants are sitting with duvets wrapped round them and condensation dripping off the ceilings. In such extreme cases the damage caused by deciding not to heat your home adequately will cost more to put right than the heating costs saved.
If all else fails, use a dehumidifier. A dehumidifier is an electrical device designed to help condensation problems by removing moisture from the air. It works by drawing in warm moist air from the room and passing it over cold coils, which causes water to collect in a moisture collector. The air that has been taken in is drier and cooler - the dehumidifier will then warm up this air and return it to the room.
These are usually used as a short term solution when excess moisture has been created, eg when a room has been re-plastered or there has been a flood. In general, as a long term solution they are not ideal, but they can help in some cases.
A dehumidifier can remove a surprising amount of water from the air (up to 2-4 litres per day) but they do make a noise and need emptying regularly. They work best in well heated houses where the humidity is high. In poorly heated houses they have little effect.
Removing condensation and mould
Ideally, you should be preventing condensation forming in the first place. However, if it does form, dry the windows and windowsills every morning, as well as surfaces in the kitchen or bathroom that have become wet. Wring out the cloth rather than drying it on a radiator.
To kill and remove mould, wipe down or spray walls and window frames with a fungicidal wash ensuring that you follow the instructions for its safe use. These fungicidal washes are often available from supermarkets. Dry-clean mildewed clothes, and shampoo carpets. Do not try to remove mould by using a brush or vacuum cleaner as you risk spreading spores.
However, moping up condensation and cleaning up mould is remedial work; the only lasting cure is to get rid of the damp air that causes the condensation and mould in the first place. Unless the cause of the problem is treated, the mould will return.
Finally, you need to be aware that if you have got mould growth, it is almost certain you have been ignoring your obligations to heat and ventilate the house correctly, which are implied if not specifically stated terms of your tenancy agreement.
Heat the whole house and ventilate by opening the windows, it's that simple.
Do not try to save money by not using the heating - redecorating will cost more than what you save in fuel bills.
Ventilate when required as indicated above.
Use a dehumidifier if necessary.
It is the tenants' responsibility to ensure that the property is adequately heated and ventilated and if you have got mould growing you are causing damage for which you can expect a deduction from your deposit. Furthermore, the damage may not necessarily be limited to the property itself - clothes may be affected, especially if packed tightly into wardrobes as well as curtains and carpets.
Constructive feedback on this information would be welcomed. If you have any comments please email firstname.lastname@example.org giving details of your suggested corrections or additions and clearly stating your name and interest (eg first year undergraduate student, postgraduate or student welfare officer). Your comments will be considered when the article is next updated.