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Top Tips for Knowing When to Use a Dehumidifier

when to use a dehumidifier

With temperatures warming and summer looming, you may be wondering when to start up your dehumidifier. During most summer days your air conditioning system will usually do a fine job of keeping indoor humidity in check. But what about those cooler days when your AC doesn’t kick in or just runs for short periods of time? That can mean higher indoor humidity and less comfort for you and your family, according to Keith Hill, manager of technical support at Minnesota Air. Here are some signs you need to use a dehumidifier.

You Notice Mold or a Musty Smell

If you’re seeing mold or noticing a musty smell that could signal mold, your indoor humidity may be too high. Any relative humidity over 50-60% allows mold to grow. Since mold spores are everywhere, you’re likely to have mold growing in your home at those levels. “When the AC is simply not running enough to take the humidity out of the air is when the moisture in the home may climb to 50% or higher," Keith explains. "That not only feels uncomfortable (cool and clammy), but allows mold and mildew growth.”

Is that mold growth troublesome? That depends. How sensitive are you to mold? How long does the high humidity condition persist? Is there a food source for the mold to grow more quickly? In the long run, even if mold growth is minor, it’s a good idea to keep it under control by managing your indoor humidity. For that, you’ll want to be running a dehumidifier.

You See Condensation

If you notice that your windows get foggy or there are drops of water on them when it hasn’t been raining, you may have a humidity issue. If moisture and condensation start pooling in window corners, this can start to eat away at wooden frames, rotting them or building up mold on the surface and in the cracks. You can nip that problem in the bud by turning on your dehumidifier.

Your Body Lets You Know

One of the easiest ways to know when to use a dehumidifier is to use your body as a barometer. Do you feel cold and clammy? Have you been having trouble with sneezing? Does it feel like your allergies are flaring up inside your home? If so, these are all signals it may be time to use your dehumidifier.

Selecting a Dehumidifier

Dehumidifiers are available as duct mounted or portable models. Duct mounted dehumidifiers are an integrated part of your HVAC system and cover the entire house. Portable models are standalone and typically cover a single room or smaller area of the home. Duct mounted models have definite advantages. They have higher capacity and require less regular maintenance – no collection pans to empty. Most have accurate digital controls and many can be controlled by the same thermostat that controls your HVAC system.

High performance AC systems with ECM motors and special humidity controls (like our Carrier Infinity systems) can improve humidity control on mild summer days, even allowing a little bit of overcooling to remove more moisture. But you may still need a separate dehumidifier to control humidity on those high humid, mild-temp days – whether it’s a simple portable unit or a duct mounted model.

If your air conditioner alone isn’t cutting it, try getting a portable or a whole house dehumidifier. But if you are in the market for an AC upgrade, Keith says a variable speed AC unit may solve your problems. “It modulates to match the load on the house. Since it runs very long, near continuous cycles, it knocks down the humidity to very low levels and keeps it there,” he says.

The ENERGY STAR website has a list of some of the conditions you’ll see in a house that has humidity issues; check it out here. For more information on what you can do to battle humidity in your home, talk to one of our local experts at

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