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With Covid-19 sadly not likely to disappear any time soon, achieving the correct ventilation of workplaces is critical to mitigate the spread in future. Hywel Davies of CIBSE discusses the issues for designers
ovid-19 is not going away any time soon. Immunologists, infectious disease researchers and virologists expect the virus to circulate and evolve in the global population for years to come – much like influenza and the four endemic human coronaviruses that cause common colds.
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For those involved in the design of new buildings and the modification and refurbishment of existing buildings, the continued presence of coronavirus makes it essential that offices and public buildings are designed with effective ventilation to create a safe working environment. Ventilation is needed to combat infection because there is a growing body of evidence that appears to show that the SARS-CoV-2, the virus that causes Covid-19, can be spread by very small particles (aerosols) in a similar way to that of cold and flu viruses. Aerosols – alongside larger droplets – are released by an infected person when they cough, sneeze, talk and breathe. The larger droplets fall to the ground within 2 metres of the source, which is why social distancing is recommended. Smaller aerosols can stay airborne for hours, which enables them to travel longer distances where they can infect secondary hosts. In a well-ventilated room, air supplied to the space will help dilute the concentration of aerosols, while extracting air will assist in the removal of airborne pathogens to outside – helping reduce the possibility of inhalation by room users and their deposition on indoor surfaces. The provision of good ventilation has other benefits; bringing a stream of outside air into a space and removing stale air helps create a healthy indoor environment for occupants. In addition to reducing levels of illness, this will also
help improve concentration levels, and increase productivity. By contrast, in rooms that are poorly ventilated, the concentration of aerosols and airborne pathogens will inevitably be higher, putting occupants at risk of infection; a risk that will increase in line with the amount of time spent in the space. When it comes to the design of new buildings, the Building Regulations require that an adequate means of ventilation be provided in a building. In England, ‘Approved Document F: Ventilation’ sets out what is considered, in ordinary circumstances, to be adequate ventilation, while in the devolved nations there are alternative regulations and guidance in place.
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The minimum ventilation rates required by the current Building Regulations should be effective in helping prevent the spread of Covid-19, where the ventilation system has been designed by a competent engineer and installed appropriately. However, we recommend that systems be designed to enable outside air flow rates to be increased above the minimum needed for compliance, to further limit the possibility of airborne transmission of Covid-19 – wherever it is reasonable to do so – without causing discomfort or a significant increase in energy demand. Also, that the ventilation system should not recirculate air from one space to another.
The recommendation that systems are designed to enable increased outside
ADF OCTOBER 2021
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