Humidity recovery and control

In cold climates, outdoor air can have very low moisture content in the winter. In well-ventilated buildings, the indoor relative humidity (RH) under these conditions can be as low as 5-10%, far below optimum conditions.

Humans and indoor plants emit moisture and in offices, schools, and other building types, this moisture can be recovered, to improve indoor environmental quality.

By equipping the air handling unit with a sorption-treated rotary heat exchanger, a significant part of the generated humidity can be recovered, resulting in a more comfortable and healthy indoor climate.

Sorption rotors are best-in-class for humidity recovery

Sorption-treated rotors have humidity recovery efficiency of up to 70-90%. In cold weather, the sorption rotor recovers moisture in the return air and deliver it to the supply air, providing a more comfortable indoor climate and reducing the need for defrosting.

Sorption rotors are also excellent at rejecting moisture from outdoor air, which has a profound impact on both the cooling power demand and energy consumption.

All this means that sorption rotors are by far the best option for humidity recovery. In comparison, normal aluminum plate heat exchangers and run-around coil systems cannot recover humidity at all.

Hygrostatic rotor control

For GOLD air handling units with RECOsorptic heat exchangers, humidity may be recovered and controlled using optional humidity sensors and functions included as standard with the built in controller. Controlling the speed of the heat exchanger, taking into account the humidity of the building and the outdoor air, allows the optimization of humidity recovery.

In the winter, a drying function can be activated to avoid temporary high humidity indoors.

Sometimes extra humidity needs to be added to the room to maintain a good indoor climate. The GOLD air handling unit controller also has built-in functionality to control an evaporative humidifier or to control a steam humidifier. Depending on the location of the humidity sensor, the humidity can be controlled in the supply air, extract air or in the zone served. A weekly timer with four time channels makes it possible to switch between two configurable values (%RH). If a steam humidifier is installed and it’s equipped with an electricity meter, the energy consumption can be reported in the GOLD air handling unit’s hand-held terminal and built-in web page.

Explore our range of GOLD RX air handling units.

The importance of correct humidity levels


The short video to the left explains in general how humidity affects both buildings and human health.

To learn more about the important influence of correct humidity levels on Indoor Environmental Quality (IEQ), please explore the resources below:

Download our whitepaper on humidity

Read more about our Hygrostatic Rotor Controller