Aug 24, 2019 Last Updated 10:52 AM, Aug 14, 2019

Dan Bourke of EnviroVent discusses its recent ‘Breaking the Mould’ report

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Dan Bourke, Social Housing Regional Manager at EnviroVent, looks at a recent study of mould involving four social landlords in the South East and Midlands, including contributing factors and recommendations for avoiding and eradicating the issue.


Black mould (stachybotrys chartarum) – it is the seasonal complaint that councils and housing associations dread. It impacts on occupant health and costs social housing providers thousands of pounds every year in trying to remove it or put right the damage it causes, such as peeling wallpaper and crumbling plaster. Black mould is also the subject of a recent study by campaigning consultancy Sustainable Homes, an organisation that helps landlords and suppliers to improve the quality and environmental performance of their homes. In association with EnviroVent, Sustainable Homes has revealed its results in the ‘Breaking the Mould – Should Landlords Be Doing More?’ report.

Initial information for the study was gathered from a questionnaire sent out to residents of four social landlords and received 260 completed responses. The study was divided into two parts. Phase 1 took place in the spring of 2017 and Phase 2 over February and March 2018.

The questionnaire for residents covered various aspects of air quality, including the incidence of mould in their homes during the recent winter. The responses were then cross-referenced with building data held by these landlords about the homes themselves and also with data from Energy Performance Certificates. The study intended to identify types of buildings where mould would be likely to occur and also to look at the impact of mould on the health of occupants.

Phase 2 involved monitoring the home environment, specifically internal temperature differences and variations in humidity and ventilation rates. Problems arise in homes if insulation is upgraded or ventilation is restricted during the colder months, in order to keep the house warm. Any moisture that isn’t removed will increase relative humidity, and colder surfaces provide areas on which it can condense.

The study used a sophisticated information gathering technique to examine over 20 different factors that could contribute to the causes of mould, in order to find which were the most significant. This included the home’s size, its occupancy – including daytime occupancy and whether pets were present– levels of insulation, age of construction, as well as other factors such as glazing and heating fuels.

The factors were then ranked in terms of how much they raised the mould score. The most significant of these was found to be occupant density – the more occupants, the more likely the house was to suffer from mould. In the context of the current housing crisis where there is a shortage of homes of sufficient size for our growing families, this factor is outside of the control of residents. Poorly installed insulation was another factor, as it meant uneven surface temperatures and the opportunity for condensation to form in cold spots on walls and ceilings.

Newer, more energy-efficient homes with less temperature fluctuations and better quality insulation were found to be less likely to have mould.

Newly-built homes were found to be least likely to have mould present, as were homes that had the most loft insulation. Homes that were continuously occupied were at a higher risk of mould. Cold weather was also found to lead to a higher risk of mould as heat is conducted through the walls, making the interior cooler, so the dew point is reached more often.

Phase 2: health issues

The study found that respiratory issues were more prevalent in homes with mould. In the 139 homes with no mould, the percentage of people with a respiratory condition was 28%. If the mould score was increased by 1.5, then respiratory conditions, such as asthma, rose to 36% of residents and if the mould severity score was above 3.0, it became 63% more likely that the resident living there had a respiratory condition.

The report highlights a need for both landlords and residents to better understand the most practical ways of dealing with condensation in homes and argues that, in fact, landlords should be doing more. While residents can take practical action up to a point, it is to the landlord’s advantage to step in sooner, rather than later, with effective remedial measures.

One way of reducing condensation and eliminating black mould effectively is to install a whole house ventilation system, like Positive Input Ventilation (PIV) from EnviroVent. A PIV system works by delivering clean, fresh, filtered air into the home from a central position. The unit gently ventilates the property and dilutes high levels of humidity so that condensation and mould cannot form. It also reduces the level of harmful household contaminants, thus improving indoor air quality and creating a healthy all-year-round living environment.

Challenging assumptions about mould

The Breaking the Mould research clearly challenges the traditional assumptions about mould in homes being directly linked to resident behaviour. As the study shows, there are underlying causes of black mould such as occupant density and failed/poor insulation which are beyond the control of residents.

The study encourages social landlords to work proactively to tackle damp and mould. There was found to be a strong correlation between household size and mould due to more breathing, showering, clothes washing and cooking taking place there.

More effective ventilation systems are required to remove this extra moisture. Social landlords are challenged to review their mould compliance procedures and introduce better ventilation into buildings, as well as improving training for staff to better deal with residents’ complaints about mould.

The final recommendation was that social landlords need to gain a better understanding of residents’ demographics to prioritise space and quality over quantity and to consider tackling fuel poverty and mould together. Some landlords have taken this advice and are already rethinking their outlook and taking a more proactive and preventative approach.

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