Whole-House Dehumidifier Pros and Cons

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In winter, when the outside air is dry, a whole-house humidifier can make a lot of sense, but in summer, when the air inside and outside the house is humid, you might need a whole-house dehumidifier instead. If you had to choose between one or the other, the dehumidifier would be the better choice — because removing moisture from the air is less risky than adding it. Although both high and low humidity can make you feel uncomfortable, high humidity levels have more potential to cause damage than low humidity levels.

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Your need to raise or lower indoor humidity, of course, depends on where you live. In arid climates or northern regions that experience cold winters and moderate summers, a humidifier may benefit a house more than a dehumidifier, but it's a different story for people in southern climate zones with long, languid summers. For these people, a dehumidifier can provide a world of relief with very few drawbacks. No matter where you live, however, a dehumidifier can improve your quality of life if the relative humidity in your house is frequently over 50 percent, which is considered the upper limit of the comfort zone.

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Running an air conditioner helps with dehumidifying because it pulls moisture from the air, but sometimes, it doesn't remove enough, particularly if it's oversized for the house. An oversized system may cool the house so quickly that it doesn't stay on long enough to reduce the humidity to a comfortable level. In that case, a dehumidifier can pick up the slack, and because dry air is cooler, the air conditioner will cycle on less frequently and consume less energy.

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Signs You Need a Dehumidifier

Air is full of bacteria and fungal spores. Some are beneficial, and some are harmful, but as long as conditions are dry, they are unlikely to have any effect on people. However, when humidity is high, water is more likely to condense on walls, floors and other surfaces as well as in carpeting, and when water is present, the spores can grow into colonies. If you see mildew or mold growth on the walls, that's one of the most obvious signs you need some dehumidification in the house.

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Besides promoting mold, high humidity just feels uncomfortable. The body cools itself by sweating, but cooling can't happen if the air is too humid for the sweat to evaporate, and besides feeling hot, you also feel sticky. You might notice that crackers taste soggy and stale and bread quickly turns moldy if you leave them on the counter in open containers for any length of time. These are more indications of the need to reduce indoor humidity.

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In winter, a certain amount of condensation on the windows is normal — even if the indoor humidity is not particularly high — because the temperature differential at the glass is so large, but if you see condensation in summer, you know you have a humidity problem that could be affecting the entire house. High humidity can cause corrosion on metal doors and windows, can ruin your wood floors by making the floorboards expand and curl. And in extreme cases, it can rot wood framing and interior woodwork. In addition, pests like ants, cockroaches and termites are attracted to the moisture.

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Whole-House Dehumidifier Pros and Cons

Once you've determined that you need dehumidification, you have a choice between using portable dehumidifiers or installing one that serves the whole house. You can obviously move portable dehumidifiers from room to room as needed, but a whole-house dehumidifier connects to the HVAC system and serves the entire home. There are several benefits of the latter approach:

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  • A humidistat monitors the air circulating through your HVAC system so the entire house is uniformly comfortable. You won't feel sticky anywhere, and you'll feel cooler.
  • The air conditioner will cycle on less frequently because the dehumidifier is helping to cool the air by removing moisture. One installer claims that customers have reported being able to set the thermostat as high as 68 to 78 degrees after installing a whole-house dehumidifier.

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  • The likelihood of mold growth will be reduced throughout your entire home, not just in the rooms in which you run a portable dehumidifier.
  • You'll enjoy better indoor air quality. A whole-house dehumidifier acts as an air purifier, filtering out allergens, such as pollen and dust mites, and because it purifies the entire house, you can keep the windows closed so these particles don't come in.
  • The dehumidifier is out of sight, and most models run so quietly that you can't hear them. A portable dehumidifier, on the other hand, occupies space in whichever room you put it, and most make noise.
  • Water is removed by a dedicated drain hose connected to the home's main drain or routed outside the building, so there's no need to remember to empty a reservoir, and you won't have to worry about water damage to the floor because you forgot.
  • You'll save energy. Most whole-house dehumidifiers are more energy efficient than portable ones.

The list of whole-house dehumidifier pros is much longer than the list of cons, which really has only one item, and that's the upfront costs of installing one. Units typically cost from $2,000 to $2,500 to purchase, and installation costs from $500 to $700. You can save a lot by opting for a portable unit, but you'll be sacrificing all the advantages of a whole-house one. However, it may make sense to opt for the portable unit if you live in a small house, or you don't plan to stay in your house for a long time.

What's Involved With Installation?

Professional installation is usually required for a whole-house dehumidifier; it isn't a job homeowners would normally do themselves. The most common installation method is to connect the dehumidifier to the existing return air ductwork. That way, the unit can pull air from the house, remove the moisture and return it to be cooled by the air conditioner or heat pump and circulated by the blower. One problem with this method is that when the dry air passes over the evaporator coils, it picks up moisture from the coils.

To avoid this, some HVAC professionals prefer to install a new dedicated return air vent for the dehumidifier and have it blow the dry air directly into the supply plenum. This method is a little more costly because it involves installation of extra ductwork, but it provides advantages over the traditional installation method:

  • It creates the minimum amount of static pressure, which is a measure of the resistance to airflow inside the ductwork. Keeping the static pressure low enables the dehumidifier to remove the maximum amount of moisture from the air.
  • It allows the dehumidifier to work independently of the air handler's blower motor. This means the blower doesn't have to cycle on as often, and that saves energy.
  • The air from the dehumidifier has less effect on the evaporator coils, which perform less efficiently when warm, dry air is passing over them. They don't get as cool as they should and don't remove as much moisture from the air, which in turn forces the dehumidifier to work harder.

One drawback to this installation method is that because the dry air doesn't pass over the evaporator coils, it's warmer than the conditioned air. However, this effect is usually unnoticeable, and it decreases as the system keeps collecting air from the house and recirculating it. The feasibility of this method depends on the configuration of the existing HVAC system. When the configuration isn't suitable, a good alternative is to install the dedicated return vent anyway to keep the static pressure low but have the dehumidifier blow dry air into the existing return ducts.

Desirable Whole-House Dehumidifier Features

If you decide that a whole-house dehumidifier is for you, you'll want to shop around to get the best one you can afford, and some of the features for which you'll be looking include:

  • Capacity:​ The capacity is the amount of water the machine can remove from the air, measured in pints per day. The capacity of the machine you need depends on the size of your home, the average humidity and the target humidity. The capacity of a small machine needed to dehumidify a 500-square-foot house with moderate humidity is about 10 pints per day, while a large machine that can serve a 2,500-square-foot house with high humidity would need a capacity around 44 pints per day.

  • Humidistat:​ A model with a built-in humidistat is preferable to one without. Target humidity levels change with the seasons, so it's convenient to be able to change them so things don't get too dry, especially in winter.

  • Auto restart:​ If you have a power outage and the dehumidifier switches off, you want it to be able to switch itself back on when power is restored so you don't have to remember to do it, and it will happen even if you aren't home.

  • Air filter:​ Not every whole-house dehumidifier comes with air filters, but they are important features because they keep the evaporator and condenser coils free of dust, which affects performance.

  • Noise​: The quietest models are typically those with two-speed fans.

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