Understanding Damp, Condensation and Mould
High humidity, condensation and mould are primarily winter problems which occur when the outside temperatures fall combined with rising internal humidity.
In winter, sustained periods of low temperature have a colling effect on the fabric of our buildings thus making the walls, roofs, windows and doors much colder. Many traditional period properties were constructed absent from insulation and are difficult to efficiently insulate retrospectively as such, older buildings are often at greater risk of condensation and mould problems due to their reduced thermal performance in comparison to more modern buildings.
Modern building may also suffer too. Modern buildings are constructed with draught proof double glazing and increased insulation, therefore modern properties are heavily reliant upon the provisions for ventilation to maintain a dry, healthy internal climate. The lifestyle of an average family of four is expected to produce between 6 – 14 kg of water vapour per day just through lifestyle activities therefore, when provisions for ventilation are inadequate, there is a risk that humidity levels will rise if the building fails to effectively manage water vapour produced during occupancy.
The origin of the excess water vapour contributing to a condensation/mould problem is almost always from basic ‘occupancy activities’, ie, cooking, washing, breathing, most frequently associated with a insufficient ventilation, intermittent or inadequate heating, etc.
Controlling the internal humidity requires a balance between moisture production, temperature of the air and surrounding surfaces and of course maintaining provisions for ventilation. Minor problems can in some circumstance be controlled with lifestyle changes, although the design, orientation and construction of the building may also increase the risk of such problems, therefore, improvements in heating, ventilation and increasing insulation may also be necessary.
Prolonged high humidity and condensation will inevitably lead to the germination of mould spores which are present in abundance around our homes. Spores that germinate and colonise may cause damage to the building fabric, internal decorations, furnishings and belongings. In addition, vulnerable people, particularly those with ill health (weak or compromised immune systems) may also find warm, humid environments particularly those polluted with moulds, MVOC's (micro volatile organic compounds) and other contaminants that aggravate respiratory illnesses, uncomfortable and potentially dangerous.
Mould spores are omnipresent, therefore present in abundance in every building however, spores will only germinate when conditions for growth are suitable. The ideal conditions for germination require three basic elements, these being a supply of food, oxygen and water. As food and oxygen are present in almost all environments, the key factor for germination and sustained growth is inevitably moisture.
Some moulds species (‘primary colonisers’) will germinate on substrates when exposed to conditions of just 75-80% relative humidity. Growth may also be fairly rapid, just 24 -72 hours. As the relative humidity against any surface increases so does the risk (‘secondary’ and ‘tertiary’ colonising moulds). It’s important to understand that moulds only require high humidity for germination the presence of physical water i.e condensation is not always necessary factor.
Between the months of October to April (condensation season) it is recommended the air temperature internally is maintained between 18°C - 21°C and occupants should ensure heating thermostats are set to a minimum of 16°C. External walls of the building should remain warm from heating and improvements with insulation should help to ensure the building retains heat efficiently. It is important that long draped curtains or the placement of large items of furniture against walls are avoided, as these will restrict heated air currents over the surface, thus the walls behind will generally be cooler and vulnerable.
Internal relative humidity levels should also be maintained between 40% and 60% and it is essential during the cooler months when the windows and doors are usually kept closed that provisions for ventilation are adequate.
Homes Fit for Human Habitation
In March 2018 the ‘Homes Act’ was announced which amended the prior 'Landlord and Tenant Act of 1985' by extending the Acts obligations ensuring tenanted properties are ‘Fit for Human Habitation’.
The intention of the Act is to ensure that all tenanted properties, both social and private are fit for human habitation by maintaining decent standards which do not place the health and safety of the tenants at risk. Two of the main parameters used to measure standards for human habitation include freedom from damp and suitable ventilation. This applies both at the start of the tenancy and throughout its duration. The new ‘Homes Act’ however, goes beyond the parameters of prior Act and now delivers the power to tenants to take legal action against landlords without having to wait for the Council or Environmental Health.
The vast majority of landlords already take their responsibilities and tenants risk to health seriously. The Act merely means to impose upon those who do not. Whilst landlords do have a responsibility to ensure that properties are provided with adequate means of ventilation and are free from damp, the tenants also have responsibility to ensure that facilities provided are used, and that they themselves are not contributory to the cause.