Dehumidification & Causes, Effects and What You Can Do About It

Published on: January 20, 2014

In the Southeast U.S., dehumidification is an issue that interests nearly every homeowner and for good reason. Achieving a healthy indoor humidity level benefits your health, improves your comfort and protects the physical features of your home. Managing your indoor humidity levels usually isn’t too complicated, but it helps to know your options before you make any decisions.

Warning Signs of High Humidity

Your first step is to determine the extent of your humidity problem. Using a hygrometer, a device that measures humidity, is the surest way to do this. If the hygrometer reads your relative indoor humidity at 55 percent or higher, you could benefit from dehumidification.

Keep in mind that the middle of an airy living room will have a lower humidity level than areas with less airflow. For accuracy, place your hygrometer in areas where you suspect a humidity problem, such as the bathroom or the corner of a particularly humid room. Test different parts of your home so you’ll know if you need dehumidification throughout your whole home or only in certain areas.

While a hygrometer helps, if you’ve lived in your home for a while, you can probably tell if you’ve got humidity issues based on a few common signs.

  • Condensation indoors — Moisture or fog forms on interior glass surfaces, such as your windows, sliding glass door or mirrors.
  • Water stains — You find brownish water stains on the corners and edges of your ceilings and walls. These are particularly common on bathroom ceilings and upper walls.
  • Mold spots — In the same locations prone to water stains you notice patchy discoloration due to mold growth. These patches may be nearly any color, including green, brown and orange. Mold problems are a sure sign you need dehumidification.
  • Musty odors — Your entryways, basement, crawl spaces or garage have a musty, mildewy smell. This is a sign of mold growing somewhere you can’t see, such as inside the walls.
  • Worsened respiratory symptoms — Your allergy or asthma symptoms seem worse when you’re at home than when you’re in a properly air conditioned, dehumidified building. Humidity itself along with excess levels of dust mites and mold spores are usually to blame for this.

Why Bother With Dehumidification?

If you’re already well-acclimated to the Southeast, it may be tempting to put up with seemingly minor humidity issues, but it’s not a wise thing to do. Ignoring your home’s humidity problem has greater consequences than a little muggy air in summer.

  • Health risks — In some people, high humidity alone aggravates allergy and asthma symptoms. As if that weren’t enough, humidity and warmth create the perfect growing conditions for dust mites and mold. Dust mites thrive in humidity levels above 60 percent and temperatures of between 75 and 80 degrees. Both dust mites and mold spores worsen existing respiratory conditions and can contribute to respiratory complaints, such as coughs and runny nose, in otherwise healthy people. Proper dehumidification will bring your home’s humidity down to around 50 percent, a level that kills off mites and mold.
  • Less comfortable living — There’s a reason dry heat is more bearable than the hot, sticky weather common in many parts of the Southeast. Moisture in the air reduces the rate at which moisture on your skin (sweat) evaporates, so you feel hotter than you would if the humidity were lower.
  • Wasted energy — The hotter you feel, the lower you’re likely to set the thermostat of your air conditioner. Good dehumidification allows you to feel comfortable at higher temperatures, so you can raise your A/C temperature settings and save money on cooling.
  • Building degradation — Excess moisture in the air can cause paint and wallpaper to peel and wood floorboards to warp. If mold develops behind your walls, it can rot the wood and drywall there, leaving you with a messy and expensive repair job. Humidity and mold in the attic degrade the insulation, making your whole home less energy efficient. If not caught in time, the decay can eventually cause the ceiling to collapse.

How a Dehumidifier Helps

Running a dehumidifier is the most effective way to prevent the discomfort and other problems high humidity causes, whether in a single room or throughout the whole house.

Put briefly, dehumidifiers work by pulling in moist room air, moving that air over cold tubes to condense and remove the moisture, and releasing the resulting dry air. They remove humidity from the air the same way your air conditioner does, but more efficiently.

The process happens in four main steps:

  1. A fan inside the dehumidifier draws in air from around it.
  2. The air passes over a refrigerated evaporator (cooling) coil. This lowers the temperature of the air to below the dew point, the point at which water vapor (humidity) condenses into water.
  3. The water in the air condenses onto the evaporator coil. It then drips into a water reservoir or a drain line that leads into your plumbing system or outdoors.
  4. The air, now free of excess moisture, passes through a warm condenser, which reheats the air to a comfortable temperature. The air is then released into your home.

Most modern dehumidifiers contain an internal hygrostat that monitors the air’s humidity level. The unit’s control panel lets you choose the relative humidity level that’s comfortable for you. Generally, this will be higher in summer than in winter.

The hygrostat automatically stops the dehumidifier when the air reaches your chosen humidity level. This way you won’t dry your air out excessively by forgetting to turn off your dehumidifier.

Portable Versus Whole-House Dehumidifiers

When you’re looking for dehumidification equipment, one of the most important considerations will be whether to choose a whole-house unit or portable unit. The choice depends largely on the size of the area you need to dehumidify.

  • Whole-house models — Whole-house units are typically installed directly in the heating and cooling system and drain automatically either into the plumbing or outdoors. These remove humidity from the air passing through the heating and cooling system. After being heated, if necessary, the dry air is distributed through your ductwork. Self-contained units, which work separately from the heating and cooling system, are also available. Both models dehumidify the air throughout your entire home.
  • Portable models — Portable units come in sizes ranging from floor-standing to tabletop size. They’re ideal if you have only one area, such as a garage bathroom, that experiences high humidity. Because they’re easily carried or wheeled from place to place, they’re also a convenient solution to temporary humidity problems in multiple rooms, such as the kitchen and bathroom. They’re smaller than whole-house units and require no installation, so they make an affordable alternative if whole-house dehumidification isn’t in your budget right now.

Finding the Right Dehumidifier

As with any home comfort equipment, you’ll need to do some shopping around to find the dehumidifier that works for your needs. There are several aspects to consider.

  • Capacity — A dehumidifier’s capacity indicates how much moisture it can remove from a given area in a given amount of time. Capacity is typically given in pints per day (PPD). The smallest portable units can remove around 30 pints per day, which is enough to handle damp air in a small room. The largest whole-house units can remove 140 pints per day or more, allowing them to dehumidify a medium-sized house effectively, even in wet conditions.
  • Physical features — Capacity isn’t the only difference between portable and whole-house units. Portable units are often made of plastic and collect water in a bucket that must be emptied regularly. Whole-house units are usually made of stainless steel and don’t need a bucket because they drain automatically.
  • CFM (cubic feet per minute) — The CFM rating refers to how fast the unit can process air, which indicates how quickly it can reduce the humidity in your home. The higher the CFM rating, the faster the unit works. Portable dehumidifiers don’t move air very quickly, so their CFM ratings may not be listed in their specifications. Whole-house units have larger fans, so they process air faster and manufacturers are more likely to offer the CFM ratings.
  • Operating temperature range — Dehumidifiers work more efficiently in warmer temperatures. That can be a problem if you need to dehumidify a cooler part of your home, such as a basement or crawl space. If this is your goal, check that the unit you choose can remove moisture in temperatures below 60 degrees. The average portable dehumidifier can’t do that.

For more pro tips on managing high humidity and choosing a quality dehumidifier, stop by AC Southeast®. With our Find a Contractor service, you can get in touch with a reliable, local contractor today, wherever you live in the Southeast U.S.