Open windows. Ventilated homes. In Germany, they have a word for this, Luften. It roughly translates in English to ventilate. To replace stale old air with fresh air.
The Germans are supposed to be pretty obsessed with Luften. They are known to ventilate their homes by opening up windows even at the peak of the freezing, frigid German winter.
But this old obsession has come in very handy during this current Covid-19 pandemic. While the original intent of Luften was to make homes more energy-efficient and circulate fresh air, now there are more significant implications.
It is a no-brainer that poorly circulated air can lead to different airborne diseases, especially the novel Coronavirus. An infected person who spends at least 15 minutes in a closed space with poor ventilation can infect others, even if they are more than 6 feet away.
The US CDC noted this in its circular dated May 7, 2021, saying that the risk of exposure to Covid-19 increases in “enclosed spaces with inadequate ventilation or air handling within which the concentration of exhaled respiratory fluids, especially very fine droplets, and aerosol particles, can build-up in the air spa.
What does this mean for our HVAC systems?
With a raging pandemic, one thing is clear, we need a sound ventilation system to keep new infections from these airborne viruses at bay. And indoor spaces are a Covid hotspot because a high-ceilinged room or a co-working space can have poor ventilation.
With the pace of vaccination picking up, and more people returning to workspaces, the focus is now on HVAC systems.
The HVAC system will work as the first barrier to stop the spread. But the question is: are current HVAC systems capable of preventing the spread of airborne diseases like Covid? Building operators and engineers need to look into all aspects of HVAC systems, including:
- Airflow patterns
- Filtration techniques
- Fresh air intake
Co-working spaces like WeWork are already taking steps in line with the CDC and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) guidelines.
What changes can be made to building ventilation systems?
The ASHRAE guidelines mention that “Ventilation with a combination of filtered outside and recirculated air provided by HVAC systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air. Unconditioned spaces can cause thermal stress to people that may be directly life-threatening and may also lower their resistance to infection.” Disabling HVAC systems is not recommended. However, ASHRAE does recommend increasing the amount of outside air and the filter efficiency as much as the system can handle with possible modifications to airflow patterns.
This means that the used air needs to be replaced with fresh air in the HVAC system. Using economizer cycles is an excellent way to achieve this. Alternatively, you can reset the minimum damper position to 100% open. Both these measures will ensure there is a higher amount of fresh air.
Opening up windows and doors also increases the outdoor airflow, diluting the indoor air. Placing fans near windows will ensure the indoor air is circulated out.
The CDC also recommends using high-efficiency particulate air or HEPA filtration systems to improve air cleaning, especially in hospitals and doctors’ clinics.
New HVAC technologies that can reduce viral transmission include:
- Air filters, especially MERV 13 filters
- Ultraviolet Germicidal Irradiation (UVGI)
HEPA filters and portable HEPA air cleaners are highly effective in vaccination centres, medical testing centres, gyms, public waiting areas, etc. The HEPA filters clean and reduce the concentration of airborne viruses, including SARS-CoV-2 viral particles.
UVGI is a good option to inactivate the Coronavirus, especially in places with limited scope for ventilation and filtration.
The CDC also recommends running the HVAC system at maximum outside airflow for 2 hours before and after the building is occupied in non-residential areas.
The cost involved
Reimagining HVAC systems do come with additional costs, but there are various measures that you can take based on your budget. For example, keeping windows open, disabling the DCV control, or repositioning outdoor air dampers don’t come with a cost.
For an investment of $100, you can have a fan installed near the window to increase the effectiveness of keeping windows open.
Installing HEPA filters may cost you roughly $500 while adding upper room UVGI can be between $1500-2500.
In the end, remember that each HVAC system is different. There would be lots of pros and cons and trade-offs to consider before incorporating major changes to your system. However, enhancing filter efficiency and installing UV lights or even increasing the amount of open-air, Luften style, will go a long way in stemming the spread of a vicious virus.
A graduate in architecture, Sayantan is an avid reader, reluctant writer and passionate about travelling and sports. His favourite topics while reading are design, architecture and current affairs; though business drives him to read books on management and economics, just to stay in the league.