Reducing the Transmission of Viruses with Humidification Part 3: Finding the Right Humidification Solution

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By Chad Edmondson

Now that we know that building humidification can help reduce the spread of viruses like Covid-19, it’s time to consider what type of humidification solutions are available, along with their suitability for a given facility or application.

If a building HVAC system already incorporates humidification, you’ll need to determine if it is capable of supplying 40% RH or measure the relative humidity (RH) in the building spaces using a hygrometer during a cold, dry day. It is important to confirm that the existing equipment is able to establish at least 40% RH under peak demand conditions. If you believe your humidification system is able to supply 40% RH but it is not performing, make sure that it is turned on and/or check to see if it requires maintenance. At the beginning of every humidification season you should also confirm that the tank is free of scale and operating properly. This is also a good time to see if the system due for a software update.

Options for Increasing Capacity

Assuming the system is functioning properly, but is still unable to reach the 40% target humidification after taking the above steps, it’s time to explore options for increasing its capacity. Start by contacting the manufacturer to see if the current system can be modified to increase capacity. If no such modifications exist, you have several options:

1. Add capacity with additional humidification generators if the existing dispersion method can handle the capacity.

2. Explore the opportunity to reduce the outside air volume to get to 40% RH. This could be possible if it there is an airside economizer.

3. Check to see if a humidifier can be added to an existing air-handler. This is a good place to add humidity for base loads for large spaces.

4. Install a point-of-use humidifier within the ductwork to boost humidity in specific zones.

When adding capacity, keep the following in mind:

  • Approximately 1 kW will be needed for every 3pph increase in humidification. (Figure 1)

Figure 1

Figure 1

  • The dispersion panel and hose/tubing may not be able to handle the increased capacity and may need a partial or complete replacement.

  • Non-wetting distance increases with higher downstream moisture so you must account for this within the existing system. If this becomes an issue, then you can look at raising the supply air temperature to decrease this distance. (Figure 2)

Figure 2

Figure 2

  • Modulating sensors provide steadier control than on/off sensors, so an upgrade may be helpful.

If simply adding capacity to the existing system is not going to get you where you need to be, you’ll need a new system. The good news is that commercial grade equipment can be ordered and installed within a matter of weeks. This includes both wall installed humidification systems and centralized systems that can be installed in an equipment room or on a rooftop. In either case, JMP can help you determine the appropriate size and type of equipment.