Feeling muggy indoors

By Hannah McKenzie
Feeling muggy indoors

Bathroom exhaust fans that work can help reduce indoor humidity. They are working if while running they can hold up two two-ply sheets of toilet paper on top of each other.

Q: My house occasionally feels uncomfortably humid. Would a stand-alone dehumidifier be a good way to fix this problem?

A: It is frustrating to be uncomfortable in your own home. A stand-alone dehumidifier may solve the problem temporarily, but figuring out the source of the problem will lead to a long-term solution and save you the hassle of emptying a drain pan.

First, focus on low- and no-cost efforts to control indoor humidity. Put on your detective hat and tour your home. The list is long but don’t worry, these are things you can do or check by yourself over the weekend.

  • Are exterior doors and windows, including storm windows, closed and latched? I often find unlatched windows in children’s rooms and over the kitchen sink.
  • Is the dryer lint trap and exhaust pipe clean? Does the dryer exhaust pipe go all the way outside? Use a shop vaccum (or borrow a neighbor’s) and suck out lint that has accumulated in the pipe. Clogged dryers will make a house muggy in a heartbeat. Avoid line drying laundry inside the house, too. 
  • Do your family members use exhaust fans when bathing or cooking, and turn the fans off when they are done? Do the fans actually pull air? The kitchen fan should hold up one sheet of letter size paper when running. The bathroom fan should hold up two two-ply sheets of toilet paper on top of each other when running. 
  • When the air conditioner is on, do you feel air coming out of every vent? If no air is felt, there may be a disconnection dumping cooled air into your attic or crawl space and allowing outside air into the home.
  • Is HVAC ductwork properly sealed? You don’t want outside air getting into ductwork through any size hole. Many small holes add up to a lot of leaks! Fine Homebuilding has great online video tutorials of this low-tech DIY project. Also ask yourself: Is it time to change your air filter? 
  • If you have a crawl space, is there plastic sheeting covering the soil? My husband and father spent a day bonding amidst mice and bugs as they rolled 6 mil polyethylene under our entire house, overlapping the seams by 12 inches. 
  • Are there any other places where outside air could enter your home? Focus on holes in the ceiling and floor. Is the attic door weather-stripped?
  • Are there other places where moisture is accumulating in or around your home? Have you considered roof leaks, plumbing leaks, clogged gutters or downspouts? Do you have an excessive number of plants or aquariums in your house? Combustion appliances such as gas fireplaces and cooktops also emit water vapor that should be vented from your home.

You don’t need to give up your aquarium or gas cooktop to improve humidity, but it is important to be aware of sources and take control of the situation.

If your home is still muggy, don’t run to the store for a dehumidifier yet!

Have you ever worried about the water dripping from your air conditioner’s drain line on a hot summer day? That water is a sign that your air conditioner is doing its job of removing humidity from your home. If no water is dripping from the drain line, it may be a sign that the line is blocked due to grass clippings, soil or mulch, which may cause humid air to be recycled back into the house, and that’s not the kind of recycling we want.

About the Author

Hannah McKenzie is a residential building science consultant at Advanced Energy in Raleigh who specializes in working with nonprofit developers like Habitat for Humanity to make new affordable housing energy efficient.

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