ULI Design Principle Training: Building and Disease Control

ULI Design Principle Training: Building and Disease Control

April 3, 2020

by Annie Yao (YLG Member）

On March 13, ULI China Mainland invited the expert of urban environment and high-rise buildings, Mr. Samuel Jiang, to share his insights on how design and operation could help to improve the living environment during COVID-19 outbreak. The main ways of virus transmission are droplets, contact and aerosols. This lecture focused on prevention recommendations for aerosol transmission. In addition, Mr. Jiang carried out a special analysis on the design and management of the HVAC system and answered the audience’s questions in detail.

Aerosol transmission prevention
Aerosol transmission characteristics: Aerosol transmission is not the same as “air transmission”. The virus may remain infectious over an hour after attaching on the aerosol. Reducing the concentration of aerosol will help reduce the possibility of infection. Lift management needs operators’ attention because lift cars are likely to have droplets, contact, and high aerosol concentrations.Prevent aerosol transmission through design: The methods include: using non-contact facilities and equipment such as automatic doors, non-contact elevator control systems, etc.; give streets and buildings multiple outdoor activity spaces; when design the core-tube, allows a natural ventilation in the lift lobbies and toilets.

Prevent aerosol transmission through operation: For buildings with a lot of daily visits, during the work time, the maximum fresh air volume should be reached as long as it does not affect the indoor temperature; after work, the fresh air and the exhaust system should still be open for one hour; in addition, the air conditioning system should be cleaned regularly, the windows should be opened when available, and the air purifier should be turned on.

Advices on HVAC management
VAV: Shut down the return air function and provide maximum fresh air; in winter, increasing the temperature of the supplied air can improve the living comfort level and alleviate risks of getting sick; reserved fresh air possibility is highly recommended to prevent the potential virus outbreaks.Elevators: Set the elevators in groups to provide the possibility of keeping both the life service and life disinfection of the lifts; fresh air is complimentary for lift car, and the top-down air flows is preferred; Elevator air conditioners generally use the secondary evaporation to re-evaporate condensed water to keep the air dry

Indoor Humidity: Use hygienic humidification method and target the indoor RH at a 40%-50% level

Air systems operation: If dry type fan coils are used and space moisture load is treated by outside air system, the infection risk indoor can be reduced

Fresh air heat exchangers for VRV: set a bypass for the air-side heat recovery system, and keep it open during a virus outbreak period to avoid cross infection

 

Q: At present, many office buildings have completely stopped the air-conditioning operation, but the indoor temperature is too low and the experience is poor. Can we turn on the air conditioner in the office?
Too cold indoor environment easily reduces the body’s immunity and cause diseases. The operator shall analyze the type of air-conditioning system to determine whether the air-conditioning can be turned on:

  • If the fan tray is installed in the office independently, and there is no virus carrier in the entire office, no cross infection will occur
  • For the VAV system, the return air should be turned off, the fresh air should be operated, and the hot water should be adjusted to the maximum to support to provide the amount of heat required to improve the indoor temperature
  • The full fresh air ventilation system basically has no risk of cross infection
Q: If it is a VRV system, can I turn on the air conditioner?
The working principle of VRV is very similar to the fan coil. It is recommended to add a fresh air system for the VRV system. In this way, when the outdoor air quality is not good, it is still possible to ensure that there is sufficient fresh-air indoor.
Q: How does UV kill viruses in the air?
The effect of ultraviolet light is not to kill the virus when the air with virus passes through. As virus mainly live on the surface of the coils, UV is used to eliminate the virus on the coil.
Q: We should open the window or use the air conditioner?
The air conditioner we use at home most common does not have the risk of cross infection in each room. Windows and air conditioners can be opened at the same time. Opening windows promotes air circulation, while air conditioning improves indoor comfort.
Q: Is there a risk of cross infection in using central air conditioners (AC)?
If it is VRV, we can use AC. If the air hundling unit is shared, we should not to use AC.
Q: Does the hotel air-conditioning system have the risk of cross infection?
There is low level of cross infection risk if the terminals are independent. The hotel operator needs to know whether the fresh air system has heat recovery system. If it does, there is a risk of cross infection, and the heat recovery system needs to be cut off.
Q: Can plants help preventing viruses?
It is not able to kill viruses, but may provide a good living experience.
Q: Can smart devices be added to the projects that are already under operation? Can the air conditioner be controlled by a mobile phone?
It is technically mature. In addition, many intelligent light control systems are connected via WiFi, and lift control systems can be controlled remotely too. Whether to apply smart devices is more an operation strategy than a design one.
Q: Is there any smart property management system, such as using an APP to control device terminal?
There are already such practices in the market. We predicting the next-generation property revolutions are based on the Internet of Things.
Q: From a design perspective, what else should be paid attention to the air conditioners (AC)?
The design of the air conditioner should be a system that can cooperate with windows. For example, if we install a sensor on the window, the AC system will automatically cut off the water in the coil or the VRV when the window is opened. Thereby, we can reduce the waste of energy and cost.

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