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Minnesota Department of Commerce Energy Information Center
Solving moisture problems can be complicated. The problems are usually created by an assortment of causes and often require a combination of efforts to eliminate. It’s a matter of achieving a balance between adequate ventilation and adequate moisture input to create a healthy living environment.
Symptoms of excess moisture
Many signs of excess moisture are readily apparent; others are difficult to detect. One moisture symptom can have several sources, and one moisture source can create a number of seemingly unrelated moisture symptoms.

There are a number of symptoms:
. Odors increase in intensity with high relative humidity. Musty smells likely signal mold, mildew, or, in the worst cases, rot. Odors from everyday household activities that seem to linger too long may be a signal of too much moisture. Frost and ice on cold surfaces; fogging windows.

Frost or ice on any surface is an indication of trouble. Condensation on windows and other smooth surfaces can be a sign of excess moisture and the need to stop air leaks, add insulation, or otherwise warm the surface.

Another possible cause of condensation is a faulty heating plant or other flame-fired appliance, which is causing excess moisture and combustion gases to enter the living space. Physical symptoms include frequent headaches, drowsiness, or other unexplainable illnesses. This possibility should be checked immediately. Keep in mind the need for annual maintenance of all combustion appliances such as water heaters, furnaces and boilers. Equip your home with a carbon monoxide detector or alarm.

Damp feeling. The sensation of dampness is common in areas with high humidity.

Discoloration, staining, texture changes. These usually indicate some moisture damage, no matter what the material. These changes may appear as black or dark streaks or lines which border a discoloration. The area may or may not be wet.

Mold and mildew, often seen as a discoloration, may be white, orange, green brown or black. They are surface conditions that may indicate decay and are often noticed as a musty odor. Water-carrying fungi look like a dirty white or slightly yellow fan with vine-like strands. The fungus can spread over moist or dry wood, and can be found under carpets, behind cupboards, on framing between subfloors or on damp concrete foundations. Wood swells when it becomes wet
and warps, cups or cracks when allowed to dry.

Rot and decay. Wood rot and decay indicate advanced moisture damage. Wood-decay fungi penetrate the wood and make it soft and weak. Look for any type of rot or mushroom-like growths. (See Wood Deterioration page 10 ).

Sweating pipes, water leaks and dripping. Water vapor may be condensing on cold pipes, or the pipes may be leaking.

Peeling, blistering, cracking paint. Moisture may be working from outside or inside the home to damage paint. Exposed surfaces between cracks

Poor drainage is a major exterior moisture problem. Proper drainage for foundations is critical. Construction details, such as flat ledges, inadequate drip edges or bad flashing, can also cause problems. Lack of maintenance can and does lead to water intrusion through siding, windows, doors, exterior light fixtures and other penetrations.

Precipitation, humidity, soil moisture content, surface water, ground water table and outdoor water use can all change seasonally, creating problems that show only at certain times in the year. Water in the ground moves through basement floors and walls. This water then evaporates into the air inside the house. If ground water is a suspect,
use the capillary test (See Capillary test, page 4) to determine if large amounts of moisture is wicking up through the ground or coming from the interior space.

Moisture source
Bathing: tub (excludes towels and spillage)
shower (excludes towels and spillage)
Clothes washing
(Auto, lid closed, standpipe discharge)
Clothes drying: vented outdoors
note vented outdoors or indoor line drying
Combustion – unvented kerosene space heater
Cooking: breakfast (family of four, average)
lunch (family of four, average)
dinner (family of four, average)
simmer at 203°F., 10 min, 6-inch pan (plus gas)
boil 10 minutes, 6-inch pan (plus gas)
Dishwashing: breakfast (family of four, average)
lunch (family of four, average)
dinner (family of four, average)
Firewood storage indoors (cord of green firewood)
Floor mopping
Gas range pilot light (each)
House plants (5 to 7 average plants)
Humidifiers 0 to 120 + /day
Respiration and perspiration (family of four, avg)
Refrigerator defrost
Saunas, steambaths, and whirlpools
Combustion exhaust gas backdrafting or spillage
Evaporation from materials:
new construction
Ground moisture migration
Seasonal high outdoor humidity

Source: Minnesota Extension Service, University of Minnesota
Household Moisture Sources
Estimated amount (pints)
0.12/standard size bath
0.52/5-minute shower
0 +/load (usually nil)
0 +/load (usually nil)
4.68 to 6.18/load(more if gas dryer)
7.6/gallon of kerosene burned
0.35 (plus 0.58 if gas cooking)
0.53 (plus 0.68 if gas cooking)
1.22 (plus 1.58 if gas cooking)
less than 0.01
if covered, 0.13 if uncovered
0.48 if covered, 0.57 if uncovered
400 to 800/6 months
0.03/square food
0.37 or less/day
0.86 to 0.96/day
(2.08 average/hour)
0.44/hour (family of four, average)
1.03/day (average)
0 to 2.7 + /hour
0 to 6,720 + /year

6.33 to 16.91/average day
10 + /average day
0 to 105/day
64 to 249 + /day
Information about moisture in your home
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