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How to Operate Commercial Buildings in the Post COVID-19?

Updated: Oct 29, 2023

I’m missing so much the time that I could work freely with my colleagues in our fantastic workspace in Lisbon. Social life is an important part of Portuguese culture. However, respecting the COVID-19 regulations defined by governments is necessary. So, in this post, we are going to give some guidelines and insights on how to return to our offices without putting our health and comfort at serious risk. This would only be possible with direct collaboration between building tenants and managers.

Figure 1. Returning to work under the self and tenant care umbrella.

What are the possible contamination modes in the offices?

Before going into the details of virus transmission modes, let’s have an overview of the last updates on the study of the COVID-19 virus. According to [2], the size of the SARS–CoV particle is estimated as 0.08 to 0.14 μm. It is assumed that SARS-CoV-2 has a similar size. To have an imagination about the size of this virus, let’s say the diameter of SARS-CoV-2 is 600 times smaller than normal hair. In aerodynamics, such small-sized particles have higher lift forces compared to their gravitational forces. Thus, they can stay floating in the air even for several hours. The three most known contamination modes inside business buildings can be categorized as Airborne, Droplet, and Contact. Figure 2 shows the different transmission routes [3]. Small droplets (D < 5 μm), also known as aerosols, are responsible for both short-range and long-range airborne transmissions (indirect infections). Medium (10 < D <50 μm), and large droplets (D > 50 μm) are respectively responsible for the direct spray and contact contamination modes.

Figure 2. Various transmission routes of COVID-19

How to avoid contamination?

Each transmission route suggests its practices for contamination avoidance. The best practice for airborne mode is to use masks, visors, and proper ventilation. The droplet transmission can be controlled by restrictions and social distancing (> 2 m). Also, the contact mode can be eliminated by hygiene, sterilization, and behavior change.

Figure 3. Building COVID-19 contamination control word cloud.

The above information tells us that contamination by aerosols is the most likely to happen (approved by the Federation of European Heating, Ventilation, and Air Conditioning (REHVA)) but is hard to control inside the offices. Thus, besides providing hygiene kits, social distancing, and behavior awareness tooltips, the following instructions are advisable for office managers to ensure the minimum number of infections.

  1. Group meetings better to be managed with a minimum number of participants in an open or heavily ventilated space.

  2. Indoor workspaces must be highly ventilated; exclusively with fresh air and avoiding circulation, to decrease the virus concentration. You are advised to supply as much outside air as possible.

  3. Avoid using re-circulation systems like fan coils. If there are no other choices, it is recommended to keep their fan working continuously.

  4. The operation times of the central HVAC system should be extended. It is recommended to start ventilation at a nominal speed, two hours before the working time shift, and switch it to a lower speed two hours after the working time shift. It is recommended to keep the ventilation working at a slower speed during nights and weekends (do not shut it down !).

  5. Humidification and air-conditioning have no practical effect on prevention. It is observed that the virus is inactivated at 56 degrees centigrade after 30 minutes [4] which is far away from the human comfort range.

  6. Changing the filter and cleaning the ducts of outdoor air is not needed.

  7. Air cleaners with electrostatic filtration methods may work well, mostly for small spaces with less than 10 m2 area.

  8. Ventilation in toilets must be kept 24/7 in operation.

  9. Any crowded spaces with poor ventilation like toilets, changing rooms, bars, and restaurants need serious precautions.

  10. Wearing both masks and visors is recommended for staff working in crowded indoor spaces. A normal surgical mask with a visor can be an effective prevention method. For healthcare buildings like hospitals, special types of masks or combinations of masks are recommended.

  11. It is highly recommended to encourage people to use stairways (with open windows if possible) rather than elevators.

  12. Instruct building occupants to flush toilets with closed lids.

“It is declared by REHVA that until vaccine and medicament are not available, ventilation is No 1 infection control measure.”

Thus, it is better to change the dress code restriction and encourage occupants to keep the windows open, especially in places with high-risk re-circulation systems.

Although it is known that Ozone sterilization will kill the Corona-virus, Ozone is a pollutant and it should not be used for indoor air breathed by humans. One may say that using UV lamps (UVC) can work as a sterilization solution, but requires correct design, installation, and management to be effective. Of course, people should not be exposed to this type of light.

There is a lot of contradiction about the effectiveness of different types of masks. However, considering the size of the virus and detailed studies of airborne contamination, normal masks are not completely effective in preventing the small particles. The obligation of wearing a mask is more to decrease the transmission range of the particles coming out of the infected person’s mouth. In this regard, the visor can substantially increase the prevention effectiveness. Because it acts as a shield against the airflow with suspended particles. Thus, these particles can hardly reach the surface of the mask.

Energy perspectives regarding post COVID-19 in commercial buildings

Energy analytic solutions like Builtrix can support building managers to track their energy profile, before and after the COVID-19 situation. This process may take less than half an hour to convert your raw data, from sensors or electricity bills, into meaningful insights. Builtrix database demonstrates that starting from March 2020, a considerable reduction is recorded in the electricity consumption of business buildings in Portugal. Thus, during the quarantine period, the energy savings in commercial buildings are noticeable.

Figure 4. Energy efficiency levels defined for a building

The bright side of the story is the behavior change that was practiced during this period. For example, it is observed that:

  1. Lots of meetings are planned remotely and people started to learn at least one telecom software;

  2. People avoid using elevators unless it’s really necessary;

  3. People start to open windows rather than using air-conditioning and circulation systems;

  4. Social distancing would highly affect the comfort level of people in their workspace and provides better air quality;

  5. Some staff prefer taking showers only at home or they reduce their showering time at work.

Moreover, some retrofit actions are now the top priority of buildings due to risk reductions and national obligations. These types of renovations include using smart lighting, smart air-conditioning, and ventilation systems. Solutions like Builtrix support the decision-making and investment process associated with the deployment of new energy efficiency technologies by providing benchmarking, prediction, and insight services.


[1] Available online at [], accessed on 27th of May 2020. [2] Bae, Seongman, et al. “Effectiveness of surgical and cotton masks in blocking SARS–CoV-2: a controlled comparison in 4 patients.” Annals of Internal Medicine (2020). []. [3] Wei, Jianjian, and Yuguo Li. “Airborne spread of infectious agents in the indoor environment.” American Journal of Infection Control 44.9 (2016): S102-S108. []. [4] Chin, Alex, et al. “Stability of SARS-CoV-2 in different environmental conditions.” medRxiv (2020). []. [5] Available online at [], accessed in 27th of May 2020.

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