Your house can make you sick

Feeling sick? Symptoms disappear or decrease when you leave home and reappear when you return?

Maybe your house is to blame.

Some of the measures people take to conserve winter energy costs also can create health problems for those who live in the home, says Bob Schultheis, a natural resource engineering specialist for University of Missouri Extension.

"Controlling water in its liquid and vapor forms is the key to keeping the house and the family healthy," Schultheis said.

"One common mistake made in the fall and winter months is closing the crawlspace vents on the house foundation and putting bags over the turbine vents on the roof. What this does is trap excess water vapor in the house, which can cause unhealthy mold and mildew to grow. It usually appears first along the baseboards and in the corners of little-used closets."

He says a 1999 Mayo Clinic study attributes nearly all chronic sinus infections to mold. Other recent studies link mold to the dramatic increase in asthma rates over the past 20 years.

"Molds can't survive without water, so by controlling moisture sources you can easily kill the mold and help everyone breathe easier," Schultheis said.

He gives the following advice for recognizing and curing high-moisture problems in homes:

  • Use a humidity gauge to check indoor humidity levels. The ideal range is 30 to 50 percent. Humidity below 30 percent, besides the annoying static electricity in the carpet, may result in a scratchy throat, an unproductive cough or a bloody nose. Above 60 percent, excess moisture will condense on the windows and the carpet will feel clammy to bare feet.
  • Make sure the ground around the house slopes away 6 inches in the first 10 feet. Add or fix missing or faulty gutters, and direct downspouts well away from the house foundation.  (See Figure 1.)
  • Put down 6-mil plastic sheeting on the crawl-space floor to prevent as much as 20 gallons of water a day from moving up into the living area of the home.
  illustration: sectional view of crawl space shows methods of reducing moisture problems

Be sure the foundation and roof vents are open to give good air circulation and to allow moisture to escape. Provide at least 2 square feet of crawl-space vent for each 450 square feet of floor area, and 2 square feet of attic vent for each 150 square feet of attic area. This ventilation also will control lung-cancer-causing radon gas, if it's present. Insulate any pipes that might freeze in cold weather.

  • Houses on upland slopes are often built on soils with a "perched" water table, causing subsurface water to seep under the foundations. Divert this water away from exterior walls by digging a trench, 1- to 2-foot-wide, down to the footing and installing perforated PVC plastic drain tile along the footing. Run the drain downhill to daylight, then line the soil side of the trench with permeable landscape fabric. Refill the entire trench with 1.5- to 3-inch-diameter gravel back to the top of the ground. Another option is to install a curtain drain on the upslope side of the house to intercept and divert water runoff away from it.
  • Install a sump pump under houses with seepage problems that can't be located. The pump will automatically collect water inside the house and return it to the outside.
  • Make sure the range hood vent, bathroom fans, laundry dryer vent, air conditioner drain, and any combustion appliances exhaust to the outdoors.

For more details on home maintenance, contact your county University of Missouri Extension center in Missouri counties. Additional information is available from the organization's publication system on the Web at or the Environmental Protection Agency Web site on indoor air quality at

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Revised 2015-03-24 by Robert A. Schultheis, Natural Resource Engineering Specialist, University of Missouri Extension Center - Webster County, 800 S. Marshall St., Marshfield, MO 65706  Phone: 417-859-2044  Email: