Social housing
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Stopping mould in its tracks
Dan Bourke, social housing regional sales manager at EnviroVent, looks at the issue of how to prevent condensation and mould growth in social housing
windows, loft and cavity wall insulation to make them more thermally efficient. In many ways this has made homes more comfortable and affordable to run, but a largely unforeseen problem has arisen – that of poor indoor air quality. This was highlighted recently in the ‘Breaking the Mould’ report produced by Sustainable Homes, a campaigning consultancy that helps social landlords and suppliers improve the quality and environmental performance of their homes. This involved 260 residents from four social landlords in the South East and Midlands.
O The objective of the study was to
reach a better understanding of how various contributing factors raise or lower the probability – and severity – of mould occurring. The aim was to help social landlords to make a quicker diagnosis of the causes of mould so that a suitable remedy might be found. The study found that mould is most likely to form in a moisture-rich environment, where water vapour can condense on a surface. It is also more prevalent in an acidic environment, where nutrients such as cellulose (abundantly found in wallpaper and in some fabrics used in clothing and curtains) are present. In most cases, mould growth starts six hours to 10 days after the provision of the right conditions, but the study found that mould grows more slowly in cold conditions. Conditions where mould will thrive include where there is a reduction in air
temperature, which means that water is more likely to condense out of the air onto the type of surface where mould will grow. An increase in temperature can make mould growth more rapid, but only if relative humidity remains high – for example, due to clothes being dried near a radiator. On the other hand, if additional moisture is not added to the air and the temperature then rises within a room, its increased capacity for water retention draws water away from moist surfaces – therefore reducing mould growth. The growth rate of black mould was found to accelerate above 70% relative humidity, but barely occurs at all below 60%. When a complaint of mould is received by a social landlord, the first action is often to issue a leaflet or other communication to advise the resident of the steps they can take to improve ventilation in the home and reduce the amount of moisture in the air. This approach is not always successful as residents may be resistant or unable to adjust their conditions or behaviour, such as drying clothes outside instead of on radiators. If this is the case, the mould often
28 August 2018
ver the last 15 years, social housing providers have been addressing the problem of cold, draughty homes which have been upgraded with new doors and
continues to get worse and at this stage, a review of mechanical ventilation provision is often recommended. This can mean extract fans are deployed in ‘wet’ rooms such as kitchens and bathrooms. Residents have been found, on occasion, to resist using ventilation systems correctly: for example, if they are perceived to be noisy or they believe that running costs are higher than they actually are. In these cases they may disable such ventilation systems without understanding how this can further increase the risk of condensation and mould. To minimise this, modern ventilation systems have been designed to be quieter than older ones and some are fitted with intelligent humidity
tracking such as EnviroVent’s intellitrac controls within the Filterless Fan range, which control the speed and power requirements
according to the internal environment. Other types of ventilation are effective at enabling a steady flow of air through the home. Positive Input Ventilation (PIV), pictured
centre, introduces air into the home, typically from the loft space, to enable sufficient air changes to occur
throughout the house. An alternative to this for new homes or those undergoing major renovations is MVHR (mechanical ventilation with heat recovery) in which warm, stale air leaving the home is passed through a heat exchanger, which pre- heats the fresh incoming air. A typical four person family produces 16 pints of water per day, over 100 pints per week, but an effective ventilation system can ensure there are enough air changes to keep the relative humidity low and prevent mould from forming. A consequence of all the humidity in homes is that social landlords’ maintenance teams are continually having to deal with issues of condensation and mould growth in homes during the colder months. This takes up a great deal of time and valuable resources and is an ongoing problem that can only be solved through the installation of active ventilation systems. The ‘Breaking the Mould’ study by Sustainable Homes demonstrates that ventilation systems such as PIV (Positive Input Ventilation), which can be retrofitted into properties, can provide the answer. PIV systems work by drawing fresh, filtered, clean air from the outside and gently ventilating the home from a central position usually in the loft, above a landing in a house, or a central
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