People are generally comfortable in homes when relative humidity ranges between 30 and 60 percent. Below 30 percent, some people experience dryness in their nose and throat; over 60 percent, the air begins to feel uncomfortably sticky. Human comfort is one consideration for indoor humidity levels, the other major consideration is keeping condensation from occurring on interior surfaces and within structural cavities like exterior walls. Excess moisture in these areas can cause problems from peeling paint, cracking of siding, deterioration of building materials and insulation. On the home's interior, moisture can promote mildew formation and contribute to health problems.

Other disadvantages of high humidity include the growth of mold, odors becoming more noticeable, and staining when condensation occurs on windows and around nails or screws in walls and ceilings. In addition, high humidity can worsen respiratory problems for people with allergies.

An early indication of high humidity levels in your home is condensation on windows. Because they are usually the coldest surface exposed to room air, they fog up first. By taking action to reduce condensation on windows, you should be able to avoid condensation problems from occurring inside the walls.

Occasional condensation or frost on windows is normal. Frequent occurrences, or periods of prolonged duration, are warnings that inside humidity conditions may be causing condensation inside wall cavities.

Inexpensive color-change relative humidity indicators can also reveal high moisture levels. These should be installed near the thermostat.

On a positive note, a certain amount of humidity in the home can help prevent dry throats and make people generally feel more comfortable because less moisture evaporates from the body thereby reducing the cooling effect. Also, higher humidity levels results in less static electricity and improved furniture maintenance as wood moisture is maintained reducing cracking and shrinkage.