Last month, authors Ben Lipscomb, P.E., and Dennis Mondul began discussing the importance of humidity for indoor comfort, air quality, and health. They covered humidity problems that impact these factors as well as building integrity, how to manage cooling humidity, and more. You can read Part one here:

In part two, they get into more detail on the technology side. They then show how you can help customers stay comfortable, healthy, and happy.

How Can You Help A Customer Manage Humidity?

Offer them a two-stage system with a multi-speed blower as an option. Many of these systems run at around 60% of capacity for a portion of the on-cycle. So they tend to run longer and more dehumidification takes place.

While two-stage systems can help to some degree, that often won’t be enough to truly maintain optimal humidity levels. That said, an improvement is an improvement. If that’s what the customer can afford, then it’s your job to make it happen.

The more exciting option for customers like Suzy may be the fully modulating variable capacity or “inverter” system.

Indoor humidity problems can lead to sore, scratchy throats and other common household ailments.
Indoor humidity problems can lead to sore, scratchy throats and other common household ailments

These systems can reduce capacity even further, resulting in very low cost, longer runtimes, and much better dehumidification over a wide range of conditions.

They can also help maintain a humidity setpoint that allow the system to run for dehumidification, as long as the temperature is above the lower limit set-up at the thermostat.

Let’s address the humidity problems this way. By design, an inverter system adjusts capacity base on the load.

Therefore, when outside conditions require the removal of 18,000 Btus per hour, a three-ton system adjusts the compressor and blower to operate more like a 1.5-ton system.

This allows the removal of heat and removes the proper amount of moisture due to the longer run time.

In fact, Suzy can now set the system to provide a stable 50% RH along with a 75°F temperature set point.

Once Frank and Suzy understand why she is uncomfortable in her home and understand that an option is available that resolves the issue, they may insist that you install a variable capacity system.

High Indoor humidity can cause the HVAC system to run too long

This occurs far more often than experienced contractors might suspect.

Low Humidity in Heating Season

The obvious solution for adding humidity in the winter is to add humidifiers. Many folks do this by buying a cheap standalone humidifier.

In Northern Montana, Ben doesn’t need central air in his home, so he has gone with standalone humidifiers. At first, he and his wife bought a single humidifier from a box store for around $30.

It turns out that these humidifiers are only designed for a single small room, such as a bedroom. These devices also run out of water requiring refills at least once or twice every day.

After dealing with humidity problems caused by dry air in every room for years, he bought another similar unit for his bedroom. Ben also bought a larger one for the main living area. With these three humidifiers, he can keep the indoor humidity between 35% and 45% RH all winter. But they must remember to fill them at least once a day.

Furthermore, standalone humidifiers also require regular cleaning to prevent the build-up of hard water deposits and bacteria. To be honest, it’s quite a hassle to regularly fill and clean three humidifiers!

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