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Property Hawk

Condensation and Mould in Rental Properties

Let me make one thing clear - condensation is NOT the same as damp. 
 
Damp is usually caused by some sort of structural defect. The resolution of damp will largely be the responsibility of the landlord, whether through maintenance of the property or the installation of a damp proof course.
 
Condensation is not so clear cut. It is typically caused by issues of poor ventilation in the rental property and is more often due to the behaviour of the tenant.
 
Though condensation is not necessarily the direct responsibility of the landlord, it is likely to be in their best interest to advise or assist a tenant to reslove any issues.  
 
Condensation in itself isn't a problem, but the black mould that can result from excessive condensation is. This black mould, called Stachybotrys chartarum, is caused by excessive condensation. It is toxic and can cause tenants respiritory problems over time.

The rise of condensation issues

In recent decades rental properties, particularly older properties, have seen cases of black mould growth increase. Ironically, the cause of this rise is often down to improvement and refurbishment of older properties. Their improved insulation,  installation of UPVC double glazed windows, better draft exclusion and greater wall insulation leads to them becoming increasingly air tight. The reducing of drafts has caused an insufficient air flow in properties that has resulted in an increased prevalence of condensation issues.
 
When moisture created within a rental property is not effectively ventilated, it needs to seek to condensate on the coldest availiable surface, typically the interior surface of an outside wall.
 
Often tenants assume the grey stains that have appeared on a wall are caused by rising damp, sometimes it is, but more often than not these mould patches are a result of condensation.

Why is condensation a problem in a rental property?

As landlords the aim is to make a rental property as draft proof as possible.  The latest regulations from the EU the European Union Directive 2002/91/EC relating to the energy performance of buildings contained within the EPC even measure the energy efficiency of a property and not having double glazing is one of the things a landlord will be marked down for. This is all good, but tenants need to be aware that the moisture created within a property needs to be managed.

Unfortunately, when it comes to ventilating a  property, some tenants just act daft. For many tenants their primary concerns are to keep a place warm and to spend as little money as possible on their energy bills. So to them, the thought of opening a window to let out the moisture from the clothes they're drying on radiators, or to leave an extractor fan running to de-mist the bathroom often sounds alien.
 
I've lost count of the number of times I've visited a rental property because of a complaint of black mould growing only to find that every vent and air brick has something wedged against it. When I point the issue out to the tenant, their usual reply is "But, they're drafty."
 
In tenants defence, the issue is not only down to them. I've already mentioned the improved insulation as one issue, but alongside that, there are some other issues that have compounded the problem. The typical size of a rental property has decreased. A studio flat might only be one room, but it has all the same moisture contributors as a large house - shower, cooker hob, sink, dishwasher, washing machine and a breathing tenant. All the moisture but in a far smaller space and think about it, who likes to listen to a whirring extractor hood whilst watching the telly.
 
Put simply, tenants often exacerbate the issue of condensation in a rental property. 

How does condensation occur?

Condensation occurs when moist warm air comes into contact with colder dryer air, or when it hits upon a surface which is at a lower temperature. The moisture which is naturally contained in the air then turns from an invisible gas back into a liquid i.e. water.
 
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.
 
Moisture in the air comes from a number of sources. In a five person household there is about 10kg or 10 litres of water put into the air every day ( that's without taking into account of any heating) i.e.
 
    •    Breathing (asleep) 0.3 kg
    •    Breathing (awake) 0.85 kg
    •    Cooking 3 kg
    •    Personal washing 1 kg
    •    Washing and drying clothes 5.5 kg
 
Moisture can also be drawn from the structure of the building from below the floor or the walls/ceilings into the air. Problems with the structure of the building due to its’ method of original construction or as a result of structural failures can mean that its moisture content is unnecessarily high.
 
Showers are large emitters of water vapour and where tenants are sharing, it’s essential to install an extractor fan to increase ventilation.  However, to reduce the amount of moisture in the air nothing beats opening the window. A task that many tenants, particularly in ground floor accommodation are not always keen to do.

Causes & lessons for landlords about condensation

Typically it is a number of contributory factors:
 
    1.    The installation of central heating. The replacement with storage heaters with a more powerful heating system such as gas central heating can potential exacerbate any condensation problem. This is because it will lift the average temperature in some parts of the property which means more water vapour can be carried in the air. This means that when the cold part of the structure is reached by this moist air. Then even greater quantities of condensation are laid down than would have been possible with a less powerful heating system.

    2.    Intensity of occupation. One objective of any landlord is to maximise their rental income. This can often be achieved by letting to a number of sharers. Having more people in increases the amount of moisture coming from breathing, showering, cooking, cleaning, etc.

    3.    Nature of occupation. Where a property is occupied by young professionals it is often poorly ventilated. This is because they are often out during the day and when they return and it is dark and cold they do not ventilate the property. The result is that no ventilation of the property occurs during day or evening hours.
 
The fact that the property had UPVC windows exacerbated the problem. Whilst sealed double glazing undoubtedly improves the heat retaining properties of the building it also turns the buildings into a sealed vessel preventing any exchange of air. This is particularly the case with more modern building which were designed to higher insulation standards than older say Victorian properties.
 
 

What can landlords do to prevent condensation and mould ? 

There are a number of things that landlords should ensure if they want to avoid condensation and mould becoming a problem:
 
    •    Lawyers would always highlight the need to have an appropriate clause in the tenancy agreement to safeguard your property. However, the problems of monitoring and proving non performance against the standards make enforceability virtually impossible. The landlord however does have an obligation under section 11 of the Landlord and Tenant Act 1985 to repair the property

    •    The realities are that many professional tenants exist in a world of air conditioning – in their car at work during their socialising in bars and restaurants. Therefore, the concept of opening windows is alien to them. This is particularly true when a tenant occupies a house or ground floor apartment where security issues also come into play. Landlords need to encourage a tenant to air and ventilate the property even through using clauses in a tenancy agreement.  If a landlord presents their student with a tenant pack then reference to good ventilation practice would be a good idea

    •    The real solutions are therefore going to be structural. Firstly, landlords need to appreciate that UPVC is not the panacea to all window requirements. In buying a property with UPVC particularly one that was upgraded, a landlord needs to examine what kind of ventilation exists and where it is. Even modern properties where UPVC glazing is accompanied with trickle vents to allow ventilation these can be closed meaning that they will only be effective if the tenant uses them. If the ventilation is not adequate then the landlord needs to add in some kind of passive ventilation to ensure adequate air flow and water vapour removal. Otherwise condensation and mould growth could become a problem. The best way to do this is to insert air bricks. These can be covered with a plastic grill to allow the occupiers to control the amount of air flow. However, where these are installed then a landlord will have to ensure that the tenants use them correctly and do not keep them closed. The fail safe option is to use the basic variety.

    •    For those keen to reduce the heat loss to the property the high tech solution are mechanically powered ventilation systems. However, they may save the tenants heat but they may not necessarily save on energy bills, nor the environment, as they use power all the time that they are on. They will also be more expensive than basic air bricks and once installed require maintenance every two years.

    •    The other solution is to reduce or avoid the occurrence of cold spots. This can be done by increasing the heat in the areas where mould appears. By doing this you will discourage the depositing of condensation in these spots and prevent the resulting mould growth. This initiative should be carried out in conjunction with methods to improve ventilation in order to prevent the problem just occurring somewhere else in the property.

    •    A landlord should urge their tenants to manage the condensation in the rental property by pulling wardrobes and furniture away from walls to allow maximum air circulation and prevent condensation and mould occurring in poorly ventilated areas of the interior.

    •    Closing doors in kitchens and opening windows will minimise the spread of moisture in the property.

    •    Getting tenants to keep lids on saucepans to reduce the amount of moisture released into the atmosphere.

    •    Tenants sould keep the bathroom doors closed when bathing.  Showers generally release more moisture into the air, so a mechanical extraction fan will help reduce this.

    •    Tenants should be aware that where they use the radiators to dry clothes they need to increase the ventilation by opening windows.  Drying clothes outside is always preferable or using a spin dry which vents externally will all help reduce the moisture released into the building.

    •    Where the condensation problem is particularly persistent then a dehumidifier which extracts moisture from the air may help counter the problem.

    •    Mould inhibiting paints and sprays will help prevent the growth of unsightly black mould although they will not impact on the route cause of the problem.

    •    Where mould does appear, encourage tenants to act quickly to remove it to prevent it spreading. This can be done by using a disinfectant or a fungicidal wash such as a diluted solution of Domestos.
 
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