Prioritising air quality


John Moss of EnviroVent looks at the issue of ventilation in social housing and how we may be failing a generation by not addressing it properly.

Now the lockdown restrictions have been removed, employees, school pupils and social housing professionals are going about their business as normally as possible, while exercising caution to minimise COVID-19 risks. However, one positive outcome of the lockdown is that the issue of indoor air quality and ventilation is, in some quarters, being given greater priority.

One of the key research findings of studies carried out by the European Centre for Disease Prevention and Control (ECDPC) was that poor ventilation in confined indoor spaces is associated with increased transmission of respiratory infections, such as COVID-19. Further to this, in the journal ‘Science’, scientists and engineers point out that while governments have regulations on the safety of food, sanitation and drinking water, there is much less regulation when it comes to pathogens in the air.

Professor Cath Noakes, an environmental engineer at the University of Leeds, said “Air quality is invisible to us so we ignore it, yet it affects us day in, day out, carrying respiratory diseases which affects the probability of people getting infections…spread of infection has not usually been a priority in building design.”

Natural versus mechanical

Latest government guidance to social housing providers on restricting the spread of the virus is that indoor environments – especially communal areas in flats and care homes – should be ventilated as much as possible to reduce the risk of transmission, by diluting internal air with fresh outside air.

The guidance states that extractor fans with outside vents should be used, or windows should be opened to allow natural ventilation. However, mechanical ventilation has been found to be much more effective than natural ventilation in a recent study S&P UK, called ‘The importance of good ventilation (before, during and after a global pandemic): Analysis model of the airborne transmission risk.’

The study set out to answer the question of whether natural ventilation – opening windows – is enough to mitigate infection risk from COVID-19 or is a mechanical ventilation system required? The study looked at three different cases: a classroom, a bar and an office. It revealed that the COVID-19 transmission risk is reduced by half when using mechanical ventilation compared with opening windows to create natural ventilation. In addition, the study points out that opening windows as a means of ventilation is not realistic in many cases, as it can cause issues with security, as well as with introducing into the home unfiltered, potentially polluted air from outdoors.

The report highlights that natural ventilation may vary hugely from 0 to more than 10 ACH (air changes per hour) under specific conditions. Therefore, mechanical ventilation allows a building owner to set the ventilation rates accurately according to the requirements of British Standards. It showed that the ventilation requirements set by British Standards can reduce by half the infection risk when compared to relying on opening windows. If a lower infection risk is desired, the installation must then deliver higher ventilation rates than those defined by the standard. The issue is that the standards were not devised in the context of a global pandemic with the associated risk of airborne transmission.

Interestingly, the classroom study revealed that mechanical ventilation delivered ventilation rates according to the standards and managed to eliminate most of the viral concentration during a playground break (30 minutes) as well as completely removing the infectious particles during a two hour-long lunch break. In comparison, in a natural ventilation scenario, open windows are not capable of completely removing the concentration of virus during any of the breaks.

The results show the importance of adequate ventilation and reinforce the advantages of mechanical ventilation systems. In particular, mechanical ventilation allows for higher ventilation rates than natural ventilation (in most cases), which leads to a lower infection risk.

Although the study was on classrooms and commercial locations, it just goes to show the benefits of mechanical ventilation in reducing and eliminating transmission risks in any situation, such as in homes or shared residences, compared to natural ventilation.

As an industry we are gearing up to meet the current and future needs of social housing providers who will be tasked with ensuring that public housing is sufficiently ventilated to protect occupants from disease and ill health.

In fact, some housing associations have been aware of the health benefits of integrating mechanical ventilation within their housing stock for many years now. They recognise how it helps to reduce the burden on their maintenance departments in the winter months with issues of condensation and mould growth in homes, as a result of poor ventilation, leading to exacerbation of health complaints, such as asthma.

PIV systems

Whole house Positive Input Ventilation (PIV) systems can easily be retrofitted into houses or apartments. They supply fresh filtered air into the home to ventilate the whole property. This method delivers air into the home which dilutes, displaces and replaces high humidity levels, which not only controls condensation but also improves indoor air quality. PIV is most commonly fitted into renovated and retrofitted properties and good quality, compliant installation is essential.

As we are in the middle of the heating season, it is likely that many social housing providers will be dealing with issues of condensation and mould growth in tenants’ homes. Addressing home ventilation by having a retrofit PIV system fitted can make a huge difference, not only to a property but to its occupants. It means a reduced risk of virus transmission, improvements to respiratory conditions, such as asthma – which are often due to humid environments creating mould growth – and less damage to the fabric of the property; all of which make ventilation well worth prioritising.

John Moss is sales director of Home at EnviroVent