How To Add a Dehumidifier to HVAC System

For large homes and commercial spaces in high humidity areas, a dehumidifier is often a necessary addition to the heating, ventilation, and air conditioning system. Excess humidity makes your home a breeding ground for mold, mildew, dust mites, and other microorganisms. If left for long, it can become harmful to your health and damaging to different materials in the house. 

While both cooling and heating can have a dehumidifying effect on the air, neither is equipped to handle huge amounts of moisture at once. To prevent any further harm, a whole-house dehumidifier can be added to your HVAC to remove excess moisture before sending the air back to different rooms through ducting.

Unlike portable units, a whole-house dehumidifier adjusts the relative humidity throughout your home to maintain your preferred setting. For simple and precise humidity control throughout your home, add a whole-house dehumidifier to your HVAC. This type of dehumidifier comes in a range of sizes typically packed in a compact, heavy-duty structure. Also unlike its portable counterparts, it may require professional installation for an additional cost. 

What is a Whole-House Dehumidifier and How Does It Work?

A ducted whole-house dehumidifier is added to the HVAC to provide more precise humidity control throughout the house. Instead of using multiple dehumidifiers for each room, installing a whole-house dehumidifier allows for a simple operation and can even save you money in the long run. 

Like portable dehumidifiers, whole-house units can be classified into two main types depending on the method of moisture removal they use: refrigerant and desiccant.


A refrigerant dehumidifier relies on condensation to draw out the moisture from the air. The working principle is similar to that of an air conditioner with a compressor that pumps the refrigerant through the metal coils. It’s not too different from your standard portable dehumidifier, only at a much larger scale. 

It draws the warm, moist air through the ducts, then the air passes through a filter to remove dust and other particles. The warm air blows over the cold coils, cooling down and losing hold of its moisture. The water vapor condenses, drips into a tray, and drains through a hose. The dry air is then reheated and sent back into the system.

The refrigerant type typically works best in warm and humid climates, although high-capacity whole-house dehumidifiers are built to work in harsher conditions than regular portable units. Since they produce gallons of condensate per day, there are risks of forming frost when temperatures drop too low. 


The other type of dehumidifier is more commonly used for commercial applications. A whole-house desiccant dehumidifier uses some kind of hygroscopic substance, usually silica gel to extract moisture from the air through a process of adsorption. It has a desiccant wheel filled with silica gel. There are two separate air streams: the process air and reactivation air. The process air is drawn into the dehumidifier through a fan and sent through the process zone of the rotor, where the moisture transfers from the air to the desiccant. 

The reactivation air may be drawn in through a second fan or taken from a part of the already dried process air. The heater warms the reactivation air before it passes through the saturated desiccant. The moisture is again transferred from the desiccant to the air, thus renewing the desiccant. Instead of producing condensate, the warm, humid air is vented outside through ductwork. Since there is no condensation, desiccant dehumidifiers work well in lower temperatures and humidity levels, making them suitable for different commercial applications.

Signs You Need to Add a Dehumidifier To Your HVAC

High humidity creates the perfect environment for the growth of mold, mildew, and dust mites, which can trigger allergies, asthma attacks, and other respiratory issues. Over time, it can also damage your furniture and house structure. 

Remember that the optimal relative humidity range is from 30% to 50%. Anything beyond this range can have negative impacts on your home. If the humidity is often 60% or higher, this may be a sign that you need a high-capacity dehumidifier in your HVAC. It helps to have a hygrometer to monitor the humidity levels, but there are also other ways to know when you need a dehumidifier.

Watch out for some of the common signs of high humidity, like condensation on windows, and even water stains or damp spots on the walls and ceiling. Musty or moldy odors are another sure indicator of excess moisture. Mold spores spread through the air and may lead to allergic reactions such as sneezing, runny nose, and difficulty in breathing. 

In worse cases, you may find visible mold growth on walls or furniture. Little dark spots on the bathroom walls or around the toilet and bathtub are some of the most common types of mold. Wood, fabrics, and other porous organic materials are most vulnerable to mold. If you can’t find the source, mold could be hidden behind furniture, under the carpet, or between walls and insulation. Lastly, too much moisture can cause wood to warp and rot. It can also lead to metal rusting and corroding. 

Look for these common signs of humidity to find the right solution for your home. Adding a dehumidifier to HVAC systems ensures that it can cover every corner of the house, especially the dampest parts like the basement or crawl space.

Benefits of a Whole-House Dehumidifier

High humidity is not only uncomfortable, but it can also have a negative impact on your health. A dehumidifier reduces humidity and eliminates mold spores, dust mites, and musty odors in the air. This improves indoor air quality and reduces the risk of allergies and other related conditions.

Proper humidity also helps protect the structural integrity of your property. Drywalls and hardwood floors are especially susceptible to excess moisture. Maintaining the right humidity levels prevents potential damage brought by the effects of moisture on different materials.

When the air is too hot and humid, your air conditioning unit alone may not work effectively. While the air conditioner can help reduce humidity, too much moisture in the air makes the job a lot harder than it should be, leading to less efficiency and higher cooling bills. 

On the other hand, on cold rainy days, you may not even need your air conditioner. You may want to use your heating instead, however, it may still not be enough to drain the excess moisture. Adding a dehumidifier to your HVAC allows you to adjust the humidity level independently, improving the air conditioning and heating efficiency of the system.

Although it costs more on the initial purchase and installation, investing in a whole-house dehumidifier will save you money in the long run. 

How to Install a Whole-House Dehumidifier

When installing a whole-house dehumidifier, it’s highly recommended to hire a professional for this task. Some models can be particularly difficult to install on your own. In some cases, the manufacturer may void the warranty if the unit is not installed by a licensed HVAC contractor. Although it may cost you more, it is a lot safer to have your dehumidifier installed by a professional. With that said, here are two ways to install a dehumidifier in an HVAC system.

Dedicated Return to Supply Installation 

This is the best way to install a whole-house dehumidifier that can benefit the entire home and the HVAC system itself. The air handler forces air into the evaporator coils, but using this type of installation, the dehumidifier will not use the air handler fan. The air from the dehumidifier unit is released directly into the supply instead. This allows for higher efficiency and less interference between the dehumidifier and air conditioner in your HVAC.

However, you might notice that the dehumidified air feels warm. This is actually normal even for portable units. As the dehumidifier removes moisture, it releases warm, dry air, which can help improve the efficiency of your air conditioning. If you feel it’s too warm for you, simply run the fan or AC to work in combination with the dehumidifier to maintain the most comfortable indoor environment.

Dedicated Return to Existing Return Installation

There is another method to install a whole-house dehumidifier in your HVAC. You can add a dehumidifier to your HVAC by using a dedicated return duct. The dehumidifier’s return ducts are then attached to the HVAC system’s existing return. This installation method makes use of the air handler to push the air throughout your home. Although just as effective, this method does not help maximize the efficiency of the entire system.

Dehumidifier Maintenance

Once installed and set up, remember to observe proper and timely maintenance to keep your dehumidifier functioning in excellent condition for a long time. This should include cleaning its exterior to prevent the buildup of dust and other impurities in the air. The air filters must also be washed or replaced according to the guidelines indicated by the manufacturer. More specific instructions are in the unit’s manual.


Investing in a whole-house dehumidifier may be a necessity for those who live in a highly humid place. Dehumidifiers come in many sizes, but if you want to dehumidify the entire house at the same time, you can do so with a whole-house dehumidifier. If you do decide to get a whole-house dehumidifier, choosing and installing the unit will not be as easy (nor cheap!) as a portable dehumidifier. 

Besides the capacity and many other factors, the installation of the dehumidifier can affect its efficiency and effectiveness. To make sure you’re getting the most out of your investment, the dedicated return to supply installation is the best method for your dehumidifier. It can also be modified to provide fresh air ventilation to the system. In any case, we suggest you leave the job to a professional. Although it can be expensive depending on the size of the unit, professional dehumidifier installation can save you a lot of time.

Related Articles