First Response: What Can We Do Now?
Part of the Pandemic Paradigm Series: Buildings Through a COVID Lens
Effective heating, ventilation and air conditioning systems have always been part of maintaining a healthy building environment, and with the impact of COVID-19 and the unique way the virus is spread, it has never been more imperative that HVAC plays a vital role in keeping occupants of buildings safe, especially as people begin to return to the office and other commercial environments.
COVID-19 has three known contamination routes: person-to-person transmission, which could be direct, or indirect through surfaces, airborne transmission through droplets, and faecal to oral whereby particles from the toilet can enter people’s respiratory systems when using bathrooms.
There are several methods to counteract these routes of transmission. The risk of the virus spreading from person-to-person can be lessened where there is a focus on smart technology in buildings. As for transmissions via surfaces, scientists have emphasised copper’s antibacterial properties, with COVID-19 surviving just a few hours on copper, compared with a number of days for steel or plastic.
To dilute airborne contamination, the Chartered Institute of Building Service Engineers recommends running ventilation systems at a higher flow rate. “This may require changes to C02 set points for both mechanical ventilation and automated windows,” it states in its COVID-19 Ventilation Guidance.
Chinese and American academics looking at outbreaks in the Chinese province of Zhejiang found that airborne transmission of the virus may have taken place in 48.3% of people in a badly ventilated office. Essentially to stop the spread of COVID-19, ventilation needs to be increased and more fresh air needs to be brought in. This could be as simple as just opening the windows.
The risk of contamination via recirculated air can be mitigated with a higher level of filtration such as F9. However, this system involves great energy use to overcome resistance, and so may need to stay on outside of normal working hours. CIBSE’s COVID-19 report also states that, “Recirculation of air within a single room, where this is complemented by an outdoor air supply, is acceptable.”
The BCO also recommends that fan coils, which recirculate air locally in the occupied space, “should be frequently and thoroughly cleaned and where condensation occurs, drain pans and traps should be maintained frequently to prevent growth of bacteria and mold.” It is also a recommendation that HepVo traps are installed on condensate systems that drain into waste pipework. As far as chilled beams are concerned, CIBSE says that active chilled beams can be operated as normal, while with passive chilled beams there should be a good supply of air.
I would be interested to see some further research on the performance of underfloor and low level air distribution. The lower velocities and laminar air flow associated with these systems causes less air turbulence, particularly in the zone where air is breathed. This would seem to have an obvious advantage in reducing the risk of virus spread in an office environment.
The ‘mixed mode’ of ventilation will become more commonplace. When it is not high summer, the cooling can be turned off so windows can be opened. This could even eventually replace the familiar sealed building model, with this system functioning automatically with sensors.
Meanwhile, to combat faecal-oral transmission, toilet extraction fans need to be kept on high and again perhaps running the systems for 24 hours a day. Again, here use of smart technology can also help to stop the spread of the virus. The same goes for anti-bacterial coatings on bathroom doors.
There is definitely set to be more access to outside air moving forward and there is a strong sustainability argument to be made for this method. However, some of the changes to ventilation strategies being deployed for a post-COVID world will inevitably have some compromises for carbon emissions, particularly if systems are kept running for long hours. However, in the middle of a global pandemic, it’s a price worth paying. As energy saving methods (thermal wheels and plate heat exchangers) also present a risk, CIBSE recommends that these are bypassed and not used in the current environment.
Of course, some of these solutions are temporary but other, smart office elements look set to be with us for the longer term. These all affect the mechanical and electrical systems, as well as the architecture and design of buildings. We will overcome COVID-19 but we need to listen to the lessons that we are learning, for now and for the future.
- Human Coronavirus 229E Remains Infectious on Common Touch Surface Materials | mBio (asm.org)
- And finally… Copper-plated doorknobs ‘may prevent spread of coronavirus’
Poorly Ventilated Spaces Case Study