News analysis with BESA
Better ventilation needed to protect the most vulnerable
The COVID-19 crisis has highlighted the importance of using mechanical ventilation systems to reduce the risk of transmission of disease inside buildings
L
essons learned from the pandemic must prompt many building managers to rethink their ventilation strategies. Turning buildings
into ‘safe havens’ would also go far beyond reducing the risk of transmitting airborne viruses. This is also about refocusing efforts on tackling the impact of rising outdoor pollution that often combines with indoor sources of contamination to create a very unpleasant cocktail of threats to long-term health and wellbeing. Once it became clear that we were dealing with an
airborne threat, the Government’s COVID-19 advice swung strongly behind improving ventilation as well as maintaining space between people – particularly in indoor environments that are designed to support and protect our most elderly and infirm, such as residential care homes. As we start to reflect on the crisis, however, we can
see just how sharply it brought into focus long-standing indoor air quality (IAQ) problems. This was recently put into stark language by a 40-strong group of leading experts and academics who compared the current state of IAQ to the contaminated urban water supplies in 19th Century Britain that led to thousands of deaths. In an article for the journal Science, the group
lamented the UK’s lack of air hygiene regulations, which is in stark contrast with the strict public health controls imposed on food, sanitation and drinking water. They blamed the way buildings are designed, operated, and maintained for helping to spread disease, including COVID-19, and called for a “paradigm shift” in ventilation similar to the changes brought about almost 200 years ago in water sanitation and sewerage control.
Ambitious
BESA is supporting their call for a building certification scheme that follows the best advice from around the world including guidance from the World Health Organisation (WHO) on ventilating spaces. Ambitious IAQ levels should also be enshrined in domestic legislation including Part F of the Building Regulations, which is currently being revised, and the forthcoming Environment Bill. The Association is also supporting the fast-tracked
British Standard BS 40101 for Building Performance Evaluation and is urging the BSI to “aim high” in setting IAQ measures that may be followed by building designers for generations to come. The fact that many buildings – including thousands
of care homes – had to rely on natural ventilation (primarily opening windows) during the pandemic to reduce the number of aerosols that carry the virus indoors exposed a widespread weakness in the UK’s approach to building ventilation, according to BESA. “Natural ventilation is completely temperature
and wind direction dependent and likely to leave unventilated, stagnant spots around the room,” explains BESA’s head of technical Graeme Fox. “The path taken by the air is critical and will be
different depending on the layout of the space and the occupancy levels. Opening windows gives you no control over the direction of the outside air and no opportunity to filter it to remove potentially harmful pollutants coming in from outside.
BESA’s head of technical Graeme Fox “However, an engineered mechanical ventilation
approach gives the user control over the air movement and the ability to adjust the speed and direction of airflow.”
This is also the approach favoured by Professor
Cath Noakes from the University of Leeds. She is a ventilation specialist and one of only two engineer members of the Scientific Advisory Group for Emergencies (SAGE) and one of the signatories to the Science article. “The spaces that worry me the most are those that
are naturally ventilated as these are temperature and wind dependent,” she says. She, therefore, advised the Government that engineering controls should sit above the measures that rely on human behaviour such as distancing and wearing face coverings in any “hierarchy of risk control”. “This is not just about flow rates as it depends on
the size of the space. 10l/s per person is the ideal, but if people are close together and for an extended period we may need more flow rate. You can also have quite a lot of people in a large space with lower ventilation rates,” says Professor Noakes. In other words, every IAQ solution is unique to the space in question and the make-up of indoor air is a complex cocktail of potentially harmful elements. However, care home managers could start by simply measuring concentrations of CO2 to see if they
10 July 2021
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