Causes of mould and are landlords to blame?

Mould is big news at the moment following the recent coroner’s verdict that the death of 2-year-old Iwak Ishak was caused by mould within the flat in which he lived.

Landlords are being widely criticised, but are landlord’s entirely to blame? In many cases the answer is not straight forward.
First, lets start by looking at the causes of damp and mould. There are three principal causes of damp namely penetrating damp; rising damp; and condensation.

In cases where the mould is as a result of penetrating damp or rising damp this is normally due to the landlords neglect, as under most short leases the maintenance of the structure is the responsibility of the landlord.

However, in the case of condensation, which is often the cause of mould, the position is far less certain as the incidence of condensation and associated damp is also linked to occupancy behaviour namely the lack of adequate ventilation during and after high moisture producing activities such as washing, cooking, drying coupled with underheating of the property.

First, let me try and simply explain some physics. Activities such as washing, cleaning and breathing generate water vapour. The presence of this increases the air’s humidity. Simple so far but now for the tricky part – As temperature rises then humidity falls as warm air can carry more moisture than cold air. Conversely, as temperature falls then humidity rises. This relationship with temperature is the reason why humidity is referred to as relative humidity. The relationship also affects the dew point, which is the temperature at which condensation occurs i.e. the relative humidity reaches 100% or saturation. The dew point is higher for air which is more heavily laden with moisture and vice versa.

So, in homes condensation occurs on colder surfaces where the temperature is below the dew point. This may vary from 17 degrees to 7 degrees depending on the amount of moisture in the air. This condensation typically occurs behind furniture where there is poor air movement, around window reveals, within corners where there is poor air movement and cold bridging and across the underside of poorly insulated ceilings.

This is where the issue gets mixed up with landlords as cold surfaces may arise due to tenant’s underheating of spaces which is linked to fuel poverty or it may be due to ‘cold bridges’ in the building fabric where the insulation and building fabric may be below standards or in disrepair. The very presence of high moisture levels within the air in the first place may also be due to inadequate ventilation by the tenant.

Lets quickly look at each aspect in turn:

Insulation – All rented properties are covered by the minimum energy efficiency standard (MEES) regulations which provide that all rental properties should have an Energy Performance Certificate (EPC) E rating or better unless there is a valid exemption in place. There is new legislation being formulated to improve these standards but I can’t see it happening soon with the cost of living crisis dominating matters. This rating addresses all aspects of a property relating to its energy efficiency in use so not just insulation.

In my experience, however, these are a poor guide as to a properties energy efficiency as these are often inaccurate and simple do not address the plethora of issues which may still exist. For example, I recently undertook a level 3 building survey of a property and there was no wall insulation, insulation was missing from parts of the roof space and the good insulation stated was only provided to approximately 30% of the property, the rest being far poorer as the roofs were not easily accessible. The rating was a D so would meet legislation, but it should in my view have been considerably worse. I regularly see similar issues.
This is often referred to as the ‘energy performance gap’ and so when a property is subjected to more extreme patterns of occupation can easily result in condensation and associated mould issues arising. Equally when properly ventilated and heated no or limited issues may arise, hence the difficulties in treating such issues as purely the landlord’s responsibility.

Ventilation –The only way to manage moisture levels is through good ventilation. To be most effective this needs to be at source. For example, use of extractor fans and opening windows. This drives to the nub of the problem as tenants are often reluctant to open windows and loose heat when the heat costs so much to generate in the first place. Mechanical ventilation therefore needs to be fit for purpose. All too often I see cheap, noisy, under-powered extract fans installed in bathrooms and re-circulation fans in kitchen. Bathroom fans are then switched off because they are too noisy and are a nuisance when the bathroom is used in the middle of the night – that’s if the fan is linked to the lighting which is often not the case!. Fans therefore need to be correctly specified which is down to landlords investing in quality fittings so tenants can ventilate their properties in the most efficient manner.

Overarching all of this is education. Tenants need to be educated on their role in managing moisture and therefore preventing mould. All too often this is not done well enough and in the case of social housing mis-trust is rife which makes resolution all the more difficult.

To summarise, my recommendations for the prevention of mould are:

1. to ensure insulation is well detailed and properly installed which in my experience looking at properties has not been the case to date. Energy efficiency standards need to be significantly improved from the current levels and there needs to be a robust retrofit programme and, I would say this, but it needs to be led by building surveyors so this is done well;

2. to provide good quality ventilation within bathrooms, kitchens etc. so moisture in quickly and efficiently removed at source before it migrates elsewhere and causes more acute problems; and

3. Educate tenants on their role in manging moisture within the home.

Landlords have a central role in all three, but tenants need to play their role too.

Julian Record is a Chartered Building Surveyor with over 25 years experience in practice.  Julian has advised social and private landlords on damp related issues and regularly prepares CPR compliant expert reports either as a single joint expert or a sole expert for the landlord or tenant in housing disrepairs cases as well as professional negligence, building and construction disputes and neighbourly matters.  If you would like to discuss a case then please contact me and he would be delighted to help.  

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