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Avoid a meltdown by dehumidifying efficiently

It’s a sticky situation: when humidity is too high, people suffer and mold gets more of the moisture it needs to grow. Yet controlling humidity by blasting the air conditioning can send energy bills soaring, and make occupants even more uncomfortable. That’s why it’s important to choose the right kind of dehumidification system for help controlling both humidity and high energy bills.

When it’s hot outside and there’s a high sensible cooling load, a properly sized air conditioning unit runs most of the day to maintain a comfortable temperature. While it’s cooling, the system also removes moisture from both indoor air and outdoor air brought in for ventilation.

Under these circumstances, a comfortable humidity level can usually be maintained without additional dehumidification methods. Yet on mild temperature days when the sensible cooling load isn’t as high, the air conditioner will not run as long, so it won’t remove as much moisture.

The result may be a space well above 60% relative humidity (RH), and a building that feels sticky and uncomfortable, even though the sensible temperature is at a desired set point. This can be an even bigger problem if the A/C brings in humid outdoor air for ventilation.

Here is a look at how dehumidification methods can impact occupants’ comfort and your building’s energy consumption:


Lowering the set point on the thermostat beyond the desired temperature causes the air conditioning unit to run longer to reach the lower temperature. As a result, the A/C will remove more moisture, reducing humidity levels but causing wasteful overcooling.

That means employees and customers may get too cold and your energy bills go up. Although it may be the “easiest” moisture control, overcooling is the least desired method because of its high costs and chance of making people uncomfortable.

Stand-alone dehumidification

Stand-alone dehumidifiers are typically added as accessories that work in conjunction with air conditioning systems, and are often ducted into the building’s air stream to work during mild conditions when cooling doesn’t do enough. These systems remove humidity independently of the air conditioning system while the air conditioning or system fan is running.

While they allow moisture control without overcooling, these systems reject heat into the conditioned space as part of the process, which puts an additional load on the air conditioning system (and the energy bill).

Electric or gas-fired reheat

Using an electric or gas-fired reheat system to reheat the cold air stream leaving an air conditioner before it re-enters the building space removes moisture without sacrificing comfort. Reheating the air with these secondary heat sources lets the A/C continue to run in cooling mode, removing humidity when the desired temperature has been set.

There’s no problem with overcooling and humidity is effectively reduced, but the reheat operation can require significant energy consumption, which increases monthly utility bills.

Integrated dehumidification systems

Use of these systems is an energy-efficient method of removing excess humidity without sacrificing comfort, initiating dehumidification based on a space’s actual relative humidity level. Integrated Humiditrol® dehumidification systems from Lennox use this method to reduce humidity while optimizing energy control.

When only dehumidification is required, these systems shift the air conditioning system’s ratio from primarily cooling and part dehumidification to focus primarily on dehumidification, and cooling second. This happens by activating a supplemental reheat coil in the air stream that acts as a secondary condensing coil, taking some load off the primary condenser. This avoids both wasteful overcooling and the additional cost required by electric or gas-fired reheat systems.

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