Optimising building ventilation

Don Foy, a Director and HVAC specialist at the multi-discipline engineering solutions business BGEN, provides practical tips on how businesses can improve building ventilation and reduce the possibility of COVID-19 and other winter viruses circulating indoors

With Omicron variant contributing towards record cases of COVID-19 across the country, building ventilation is under the spotlight like never before. Professor Cath Noakes told the Building Engineering Services Association (BESA) national conference that the pandemic had increased understanding of how disease is transmitted around indoor spaces and raised public awareness of the importance of mechanical ventilation.

“I never thought I would see the day when the Prime Minister and the Chief Scientific Officer were talking about ventilation,” said Noakes, who is one of two engineer members of the government’s Scientific Advisory Group for Emergencies (SAGE).

Measures continue to be introduced to improve building ventilation. In January for example, the Government announced an additional 7,000 air cleaning units to be provided to early years, schools and colleges to improve ventilation in teaching spaces.

But with COVID-19 here to stay, alongside winter viruses such as influenza, organisations throughout the UK need to consider how they can improve the ventilation of their premises – whether that be an office, factory or school.

MITIGATING THE SPREAD

Eliminating the spread of COVID-19 and other winter viruses is virtually impossible, but there are a number of ways building ventilation can be improved and transmission of the virus can be reduced.

Conduct a risk assessment

Undertake a risk assessment to identify ventilation challenges specific to a building and develop a plan to improve ventilation. Given the focus in recent decades has been on minimising fresh air entering a building to aid employee comfort and optimise the energy consumption of HVAC systems, this may be a challenge, but a HVAC specialist will be able to offer support.

Balancing fresh air and employee comfort

‘Displacement ventilation’, where air is introduced in a room at a low level and extracted at a high level, using the theory ‘warm air rises’, is one of the most effective methods of removing air contaminants. However, while maintaining good levels of ventilation is important, employee discomfort should be minimised. While there is no legal requirement on temperatures in the workplace, the Government suggests a minimum of 16C or 13C if employees are doing physical work.

Currently most mechanical building ventilation systems for occupants have fresh air supply mixed with recirculated air at a high level in ceiling voids before they are supplied to the room to help avoid drafts and lower temperatures. This method however makes it difficult to remove the COVID virus from the air effectively. Therefore, additional fresh air through lower inlets should be considered.

Encourage cross room air flow

You might think opening some natural room vents fully will help to improve ventilation. However, to get the best results, open room vents on opposite sides of a room to encourage cross room air flow.

Minimise air recirculation

Unless your HVAC system is designed to mitigate the risk of COVID-19 and other viruses, keep their use to a minimum.

Air purifiers

Air cleaning and filtration units can help to reduce the airborne transmission of COVID-19 and other viruses. These should be considered in areas where it is not possible to maintain good levels of ventilation.

Check/install sensors

Think about installing sensors which can detect CO2 levels, especially in highly populated areas such as open plan offices and meeting rooms. This can provide a guide as to when additional fresh air is required. Levels should be agreed on a case-by-case basis, but it is generally accepted that the limit should be a maximum of 800ppm.

In addition to CO2 monitors, consider disabling sensors designed to optimise fresh air per employee. The standard 10 litres of fresh air per person (minimum) should be re-evaluated while we work through the pandemic.

Consider UVC light and upgrade filters

Ultraviolet (UV) light can kill the COVID-19 virus. Consider the use of UVC lights in HVAC systems (UVC lights can also be installed directly in rooms if there is no mechanical ventilation). F7 grade filters or better in HVAC systems will also help to capture SARS-CoV-2 and other virus particles.

Put pressure in the spotlight

Slightly higher or lower air pressure can help reduce virus contaminated air from stagnating. There should be a pressure differential of approximately 25 pascal units between rooms to achieve this.

Think about the environment

Many measures to improve ventilation will involve an increase in energy consumption. Heat recovery units and other technologies can help to negate this. Heat recovery units, which utilise the heat from extracted air to heat the fresh air being introduced from the outside, will help to maintain a comfortable room temperature and significantly reduce energy bills.

Finally… use common sense

If needed, open doors (where possible) and windows as required. Also, consider providing extra space between workstations in open plan offices.

THE FUTURE

While Government advice continues to change in accordance with variants, the reality is that we need to find a way to live with COVID. Optimising building ventilation can play a key role in helping society to return to some kind of normality, and in the process also help to reduce the spread of other winter viruses.