The humidity levels in your properties affect so much more than just how comfortable your employees and customers are when they’re inside. When they are too high or low they can have a negative impact on your building’s structure and people’s health. But how do you know what the right level is? And when regulations require a specific level of outdoor airflow, how do you control the humidity inside? We have the answers to some of the most asked questions about humidity and HVAC.

How do humidity levels affect your properties and the people in them?

When your properties are too humid, it can have structural implications like warped wood or mold. When it's too humid in a grocery store, it can lead to foggy freezer doors or large blocks of ice forming in island coolers. And dry environments come with their own issues: dry air means static, which can do damage to computer systems.

And for the people in your locations, poor humidity levels can mean not only discomfort, but health concerns. If it is too low, bacteria and viruses can live longer and can lead to more infections. In the middle of a pandemic, this is even more important to think about. But if it is too high, it can also lead to skin irritation, lethargy, headaches, and other health issues.

It’s all about balance—so what is the ideal level?

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends maintaining a relative humidity at 40-60%.

How do you monitor it?

Most rooftop HVAC units are able to monitor humidity, and some properties have additional sensors inside. With an Energy Management System (EMS) in place, you can remotely track levels using the rooftop units without needing additional sensors.

How do you control it?

For those unfamiliar with the inner workings of an HVAC unit, here’s a simplified explanation of how they work to control humidity.

Every unit has a coil inside, and this coil is cooled down using a refrigerant. As the air flows through the coil, it removes heat and moisture. The longer the unit runs, the more it dehumidifies a space.

Implementing a consistent preventative maintenance (PM) program can help make sure everything is working correctly, the coil is being properly cooled, and your spaces are maintaining the right temperature and humidity level. During a PM, your service provider should be checking the coil, belt, refrigerant levels, and unit run time—all of which highly impact humidity levels.

Are you doing preventative maintenance, but still dealing with less-than-ideal humidity?

Even if everything is working properly, your humidity levels may still not be where they should. Luckily, there are methods that can help control how much humidity is removed from the air.

Larger units can typically cool the air much faster, meaning the unit itself doesn’t need to run as long. While this seems like it would be a good thing from an energy consumption perspective, it can actually cause your locations to become more humid. Replacing your large units with smaller ones can help you control it.

But that’s not always the right move, especially if your units are newer and functioning properly. Don’t worry, you have other options.

Installing variable frequency drives (VFD) on your units can let you control the fan speed. A lower fan speed means more time for the air to flow through the fan, which means more time for the humidity to be removed from the air. This is a great, cost-effective alternative—especially if replacing your units is not an option.

Key takeaways:

  • The ideal indoor humidity level is between 40 and 60%
  • Energy Management Systems can help monitor HVAC unit performance and the humidity levels in your properties
  • Implementing a comprehensive preventative maintenance program can ensure your units are working properly to not only regulate temperatures, but also humidity levels
  • The longer the unit runs, the more it dehumidifies a space—this is why smaller units are often better at keeping humidity levels lower
  • Variable frequency drives are cost-effective options for controlling airflow and regulating humidity levels
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