Moisture problems

Here are some tips on diagnosing and correcting moisture problems. Parts of this story: | Introduction | Attic and mechanical ventilation | Houses on crawl spaces and other moisture sources | Caulking and weather-stripping | Basement wall condensation problems

In homes built on crawl spaces, evaporation of moisture from the earth is a major source of household humidity. The high levels of humidity in crawl spaces can be a problem in both summer and winter. Foul odors in the home or crawl space, mold and mildew growth in the interior of the home (especially in closets) and growth of fungi in the crawl space itself are signs of the problem. Covering the crawl space ground with a vapor retarder (polyethylene or heavy plastic sheets available at lumberyards) is crucial in preventing moisture problems in crawl space homes.

In addition to a vapor retarder covering the ground, crawl spaces should be provided with adequate natural
ventilation to facilitate air movement throughout the space. If a vapor retarder is present in the crawl space, 1 square foot of free vent area is required for every 1,500 square feet of crawl space ground area. Without a vapor retarder present, 1 square foot of free vent area is required for every 150 square feet of crawl space ground area.

Most crawl space vents include louvers and/or screens to prevent the entry of insects and small animals. These coverings slow air circulation and cut down on the vent's effectiveness. Thus, you will need to double the
amount of ventilation needed in most cases to compensate for this reduction. Locate vents near corners and across from one another to facilitate air movement through the crawl space.

Humidifiers

Many homeowners use humidifiers to add moisture to their homes in winter. In the past, when homes were leaky and so less energy efficient, much of the moisture generated inside the home went out with the warm air escaping around and through windows and doors.

Overly dry air-was common, and people experienced static electricity buildup on carpets and clothes, breathing difficulties due to dry nasal passages and somewhat destructive over drying of furniture. To combat this dryness, they commonly used humidifiers. Some were incorporated directly into forced air heating systems, and moisture was circulated in the home along with heated air. A second type of humidifier, the free-standing model, is portable and can be moved freely around the home to provide moisture where it is most needed. Whether you have extensively weatherized your home or not, experiencing condensation problems means you should not use a humidifier.

Construction moisture

Homeowners who move into a: newly constructed home or complete remodeling projects often experience high moisture levels in the interior as the building materials and systems dry. If it is necessary to close the house because of cold weather, the problem may seem excessively serious. Over time, the building materials will dry and a form of equilibrium will be established. In the meantime, airing the house when you can and using exhaust fans will help to move the moist air to the outside.

Malfunctioning combustion appliances

Oil- or gas-fired heating, appliances that are not functioning properly or unvented heating units can cause a buildup of moisture in a dwelling. If you suspect any combustion appliance in your home is not functioning correctly, have a repair person inspect it. Heating systems, in particular, should be regularly inspected and adjusted by a heating contractor. Oil-fired furnaces need annual inspections. Gas-fired systems, depending on their age, can be inspected less frequently, though three years is the maximum time a gas-fired unit should go without being serviced. If you use unvented space heaters in the home, follow the manufacturer's use and maintenance instructions carefully.

Cool surface condensation problems

In less energy-efficient homes, cool surfaces are readily available for water vapor to condense and collect on. Warming these surfaces by adding insulation or cutting down on the amount of cold air that can get to them by caulking and weather-stripping will lessen condensation problems.

Toilet Tank and Water Pipe Surfaces

Toilet tank surfaces are another common place for condensation to occur, particularly during warm, humid months. Warm toilet tank surfaces by either installing rigid waterproof insulation on the inside of the tank or adding a mixing valve to the cold water supply line. This introduces hot water into the tank water supply and can
help warm the tank to a level that prevents condensation. Install tubular or wrap insulation around water pipes to
prevent condensation there.

The information in this article comes from Michigan State University Extension bulletin E-2109, Moisture Problems in the Home.