How Does a Whole-House Dehumidifier Work?

For homes in humid climates, a dehumidifier is a necessary addition to your heating, ventilation, and air conditioning system. High humidity promotes the growth of mold and mildew, which can trigger allergies and damage your house structure and furniture. To prevent this, a whole-house dehumidifier processes the air from your ducts, removes excess moisture, then sends back dehumidified air to your rooms through ductwork.

In contrast to portable units, a whole-house dehumidifier helps maintain optimal humidity throughout your home. For easy humidity control no matter the climate, add a whole-house dehumidifier to your HVAC. It comes in a wide range of capacities and different types suitable for harsh conditions that a regular dehumidifier cannot handle. So if you’re looking for a dehumidifier for the whole house, we’ve gathered all you need to know, from how it works, what it does for you, and the essential features you must consider.

How Whole-House Dehumidifiers Work

A whole-house dehumidifier is simply a high-capacity dehumidifier with provisions for ducting to dehumidify multiple rooms at the same time. Adding a whole-house dehumidifier to your HVAC allows you to have more precise control over the humidity in your entire home. Instead of using multiple portable dehumidifiers for individual rooms, investing in a good whole-house dehumidifier offers greater efficiency and saves you money in the long run.

Like portable units, whole-house dehumidifiers can be classified into two types based on the dehumidification method used: refrigerant and desiccant.

A refrigerant dehumidifier consists of a heavy-duty compressor that pumps the refrigerant to the metal coils, using condensation to pull moisture from the air. A whole-house unit works similar to a portable dehumidifier except it draws the humid air through ducts from multiple rooms. The air passes through a filter and then over the cold coils. As the air temperature decreases, the moisture condenses into water. Once dehumidified, the air is then reheated and sent back into the central HVAC system. The condensate is collected in a drain trap below the unit or pumped out through a hose.

The refrigerant type generally works well in warm and humid climates, but compared to the standard portable unit, whole-house dehumidifiers typically have higher capacity and durability to work even in lower temperatures. Since they produce condensate by gallons per day, there are higher risks of frost, so take note of the unit’s operating temperature range.

Aprilaire 1820 Whole-house Dehumidifier
Aprilaire Whole House Dehumidifier Example

Signs You Need a Whole-House Dehumidifier

Humidity sometimes creeps into your home without you noticing until it has already caused severe damage. Remember that the ideal indoor humidity is between 30% and 50% RH. It helps to have a hygrometer to measure exact humidity levels in your home. If it often reads 60% RH or higher, this may be a sign that you need a dehumidifier for your home. If you live in a temperate region with excess humidity or a small apartment with poor ventilation, you can expect high humidity.

If you can’t measure the relative humidity, watch out for some common signs of dampness in your home. Condensation occurs when the warm and moist air touches a colder surface, like glass windows, usually in the bathroom, basement, or kitchen. In worse cases, you may find water stains or damp spots on the walls and ceiling.

Musty odors are another sure indicator of high humidity. Mold likes damp, dark, and cold areas and they spread spores through the air. Dust mites also thrive in highly humid environments. They can trigger allergic reactions, asthma attacks, and other health conditions. 

Little dark spots in the bathroom walls, under sinks, or around the toilet and bathtub, are a common type of mold. Wood, fabric, and other organic materials are most vulnerable to mold growth due to moisture. If you can’t find the source of the moldy smell, look behind furniture, under carpets, or between walls and insulation. 

Lastly, high humidity can cause wood to rot and metals to rust and corrode. If you see any of these signs, it calls for an immediate solution besides installing a dehumidifier. Otherwise, it can cause permanent damage to your house.

Best stand for dehumidifiers
Santa Fe Whole House Dehumidifier Example

Features of a Whole-House Dehumidifier

Whole-house dehumidifiers can only work effectively and efficiently if you find which one is best for your home. This depends on many factors including the capacity, coverage, energy efficiency, and draining options. To get the best out of your investment, consider the following features of a whole-house dehumidifier. 

Dehumidification Performance

The most important feature is the capacity or total amount of moisture the dehumidifier can remove per day. Whole-house dehumidifiers usually have a capacity of at least 70 pints up to 200 pints per day. The AHAM capacity is the amount collected at the average condition of 80°F and 60% RH, as recommended by the Association of Home Appliance Manufacturers. Take note of this as it is the most accurate representation of the unit’s actual performance. Some models may indicate the maximum capacity or the largest amount that it can extract per day at saturation (90°F and 90% RH).  

Coverage Area

It is essential to get a dehumidifier that can cover all the rooms you need to dehumidify. Higher capacity units usually have a larger coverage area but it also depends on the humidity levels and temperature. Also note the airflow, measured in cubic feet per minute (CFM), or the rate at which the unit processes the air. While it doesn’t necessarily relate to the coverage area, a higher airflow rate may be needed to efficiently cover larger spaces. 

Drain Options

Most dehumidifiers have the option for continuous draining using a drain hose (usually included with a whole-house dehumidifier). Just attach the hose onto the outlet and let the water flow down directly to a low-level drain. Some high-capacity dehumidifiers may also come with a built-in pump. This allows for automatic draining in any position.

Energy Efficiency

If you want to use your whole-house dehumidifier throughout the seasons, it’s also important to know about its energy efficiency and ensure you’re not wasting money. Look for the energy factor in liters or pints per kilowatt-hour. The higher the energy factor, the more efficient the dehumidifier. This should be indicated on the unit’s manual or you can check out the Energy Star website for more information.

Humidistat

A humidistat measures and adjusts the humidity level automatically. Whole-house units may have it built-in or mounted on a wall for remote operation. Set your desired humidity level and the unit will shut off automatically once this is reached, thus reducing your energy consumption. After a certain period, the unit will measure the humidity. If it’s higher than your setting, the unit will start dehumidifying again. This can be very convenient and even necessary if your dehumidifier is in a basement or crawl space and ducted to your HVAC.

Benefits of a Whole-House Dehumidifier

Improve Indoor Air Quality

Aside from discomfort, prolonged exposure to high humidity can have a negative impact on your health. A dehumidifier improves indoor air quality by removing excess moisture. It eliminates dust mites, mold spores, and musty odors. This reduces allergies and other symptoms caused by these air contaminants.

When the air is dry air, lower chances of mold and mildew growth occur, which is not only great for your health, but for your home’s integrity. Wood floors and drywall are especially susceptible to high humidity. Maintaining proper humidity helps prevent any damage caused by moisture and its effects on different materials.

Improve Air Conditioner Efficiency

Furthermore, during hot and humid seasons, your air conditioning system may not work as effectively. Too much moisture in the air makes the job a lot tougher for your air conditioner, leading to higher cooling costs. On the other hand, if you get cold rainy days, you may not even need to run the air conditioners often. While it may help reduce the humidity, it cannot drain enough moisture, giving you a cold and damp room. Adding a dehumidifier to your cooling system allows you to adjust the humidity level accordingly, increasing the efficiency of your air conditioning or heating units.

Although it costs more on the initial purchase, investing in a whole-house dehumidifier saves you money in the long run, compared to using multiple portable units throughout the house.

Installation and Maintenance for Whole-House Dehumidifiers

A whole-house dehumidifier can be connected to your HVAC system to dehumidify the air that passes through your ducts. To install this dehumidifier, you can add a dedicated return duct that supplies air to the unit. You may also connect the unit to an existing return duct, and then send the processed air back to your HVAC supply plenum. Although some models may be simple to install, it’s recommended to hire a licensed HVAC contractor for this job. Otherwise, the manufacturer may void your warranty.

When using the dehumidifier, you can pick the humidity setting you prefer. Most dehumidifiers include an onboard or remote humidistat so you can adjust the humidity to your desired level. Set the humidity for your home between 30% and 50% based on the ambient temperature. You can also set a timing schedule to keep the unit running only when necessary.

Whole-home dehumidifiers usually require little maintenance, but you must inspect it regularly to make sure it’s working. First, always follow the manual’s instructions for installing, using, and maintaining the unit. 

Scheduled cleaning helps to prolong the life of your dehumidifier and keep it running smoothly. As it extracts moisture from the air, it also collects dust, dirt, mold spores, and other impurities that would eventually get in the air. Don’t wait for the unit to get visibly dirty – clean it at least every month. Wipe down its exterior with a damp cloth, disinfect the drain hose, and clean the filters. 

Every dehumidifier has a recommended schedule for when to clean or replace the filter. Check the manual for filter cleaning and replacement information and put a recurring schedule on your calendar. You’ll only have to do this once. The coils must also be cleaned at least once a year, but you’ll need a professional cleaning service for this.

Lastly, most dehumidifiers work best in warm climates around 59°F to 86°F, unless specifically designed for lower temperatures. When the temperature drops to 41°F or below, most refrigerant dehumidifiers will stop working. When condensate starts to freeze, the unit will automatically defrost, but you should also inspect the coils inside to be sure. Frost buildup inside the machine can compromise its performance and even cause permanent damage. If you expect low temperatures in your area, you might be better off with a desiccant unit.

Summary

Not everyone needs a whole-house dehumidifier, but for those who live in areas with extreme climates, humidity control may be crucial. In this case, a dehumidifier is a necessary component of your HVAC system. As it keeps humidity down, a whole-house dehumidifier will improve your air conditioning efficiency and reduce the need for heating. In essence, it works just like its portable counterpart and it’s important to find the right size for the entire space you need to dehumidify. Look for the features you need to be sure that you’ll get the best whole-house dehumidifier for your home.

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