Building occupants can experience various adverse health effects from mold and mildew, including allergies and asthma. Excessive moisture is the primary cause of mold growth and can be the result of plumbing leaks; condensation buildup; splashing around sinks and baths; unventilated restrooms; or the infiltration of water or humid air through walls, windows, roofs, or basements. When moisture does not dry quickly, mold can form, and rot or other damage can occur.

Signs of potential moisture problems in a home can include:

• Condensation on windows
• Dampness on walls and mirrors in shower rooms
• Discoloration of ceilings or walls, and patches of mildew or mold
• Odor problems or a musty smell
• Peeling paint
• Dampness around building foundations, basements, or crawl spaces
• Standing water in drip pans below air conditioning units or refrigerators

Once identified, mold should be cleaned immediately to eliminate growth and avoid adverse health effects.

To remediate moisture and mold:

• Dry damp basements or other areas immediately.
• If mold is suspected within the HVAC system, turn off the fans, and have the ducts professionally cleaned.
• Fix plumbing leaks and dry all areas.
• Scrub mold off hard surfaces with detergent and water. Bleach is not necessary if the space is kept dry.
• Remove and replace moldy drywall, carpet, or other damaged finishes.
• Do not paint directly over mold. Clean and dry surfaces first.

To prevent moisture and mold issues in buildings:

• Install exhaust fan timers in showers, and encourage residents to use them.
• Ensure that rainwater does not drain to, or collect around, the building foundation. Install sump pumps or additional gutters as necessary, and direct downspouts away from the building.
• Drain air conditioning system condensate to avoid standing water.
• Insulate cold pipes where condensation occurs.
• Replace single-paned windows with double-glazed, insulated windows.
• Measure relative humidity inside the building, and set the HVAC systems to maintain 30–60% relative humidity, if possible. This may require adjusting the temperature or adding humidifiers or dehumidifiers.
• Replace moldy finishes with less absorbent materials.