Mold Web Course/Chapter 2/Lesson 2

by the Environmental Protection Agency

Lesson 2Moisture Problems

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Moisture problems can have many causes. Some moisture problems have been linked to changes in building construction practices since the 1970s. These practices led to buildings that are tightly sealed but, in some cases, lack adequate ventilation. Without adequate ventilation, moisture may build up indoors and mold may grow.

A building must be properly designed for climate, site location, and use, and its design must be accurately followed during construction or the building may have moisture-control problems. For more information on building construction for moisture control, see the Resource List.

Delayed or insufficient maintenance can lead to moisture problems in buildings. Undiscovered or ignored moisture problems can create an environment in which mold can grow. Moisture problems in temporary structures, such as portable classrooms, are also frequently associated with mold problems.

Common moisture problems include:

• Leaking roofs.
• Leaking or condensing water pipes, especially pipes inside wall cavities or pipe chases.
• Leaking fire-protection sprinkler systems.
• Landscaping, gutters, and down spouts that direct water into or under a building.
• High humidity (> 60% relative humidity).
• Unvented combustion appliances such as clothes dryers vented into a garage. (Clothes dryers and other combustion appliances should be vented to the outside.)

Some moisture problems are not easy to see. For example, the inside of walls where pipes and wires are run (pipe chases and utility tunnels) are common sites of mold growth. Mold is frequently found on walls in cold corners behind furniture where condensation forms. Other possible locations of hidden moisture, resulting in hidden mold growth are:

• Poorly draining condensate drain pains inside air handling units.
• Porous thermal or acoustic liners inside duct work.
• Roof materials above ceiling tiles.
• The back side of drywall (also known as gypsum board, wallboard, or SHEETROCK®), paneling, and wallpaper.
• The underside of carpets and pads.

You may suspect mold, even if you can't see it, if a building smells moldy. You may also suspect hidden mold if you know there has been a water problem in the building and its occupants are reporting health problems.

Building Design and Vapor Barriers

Many buildings incorporate vapor barriers in the design of their walls and floors. Vapor barriers must be located and installed properly or the building may have moisture problems. A vapor barrier is a layer of material that slows or prevents the absorption or release of moisture from or into a wall or floor. Vapor barriers can prevent damp or wet building materials from drying quickly enough to prevent mold growth. For more information on building design see the Resource List.