How to Control Moisture

The level of moisture in the home is crucial to achieving a healthy home environment. Too little moisture in the home can cause dryness of the nose and respiratory systems, while too much moisture in the home contributes to numerous health impacts, health hazards, and structural home damage. Asthma, allergies, and other respiratory illness are the main health impacts to children and other residents of homes with excessive moisture. Excessive moisture also causes or contributes to other hazards to human health such as moldcockroachesdust mites, and peeling lead paint.

Several common signs that conditions of excessive moisture exist in the home environment include:

  • Rusting metal
  • Condensation on piping and/or windows
  • Rotting wood
  • Mold growth
  • Peeling paint, wallpaper, or other blistering materials
  • Deterioration of other structural items
  • Visible water leaks and/or stains
  • Discoloration of various surfaces
  • Musty odors
  • Standing water

These signs may be clearly visible or they may be hidden in places such as behind walls, under furniture and carpets, and in crawlspaces or attics. In assessing moisture problems in the home environment, it is important to know such potential hiding places and visually inspect all areas that are reasonably accessible. A low-cost moisture meter can also be used to test for moisture in inaccessible places. See for additional information.

Moisture problems inside the home can originate from problems both indoors and out. In general, preventing and eliminating moisture control problems involves removing, diverting, blocking, or otherwise controlling the source of moisture while also providing adequate ventilation. Some specific tips to prevent and eliminate excessive moisture in the home include:

  • Regularly clean and maintain gutters, and ensure that they drain away from the foundation of the building structure.
  • Install and run exhaust fans in the bathroom and kitchen or open windows for adequate ventilation.
  • Vent all fans and appliances to the outside of the home.
  • Do not arrange or store items (furniture, storage boxes, etc.) so that they touch the interior side of exterior walls.
  • Dry all clothes in a dryer that vents to the outside or use a clothesline outside.
  • Cover dirt floors in basements and/or crawlspaces with plastic or other type of vapor barrier.
  • Repair all plumbing leaks, roof leaks or problems, and cracks in foundation walls as soon as possible.
  • Ensure that soil and landscaping near the structure’s foundation are graded away from the structure.
  • Install floor drains or sump pumps in basements as necessary.
  • Keep the temperature inside the home comfortable—not excessively hot in the winter or cool in the summer. Drastic changes between indoor and outdoor temperatures can contribute greatly to moisture problems.

Further precautionary steps can be taken to control moisture in the home environment during initial construction or any subsequent renovations. The New England Asthma Regional Council has developed excellent guidelines for building healthy homes and also offers links to numerous other healthy homes building resources.

Sources and Additional Information:

A Brief Guide to Mold, Moisture, and Your Home –

Building Science Corporation Building Design by Climate Guides –

Community Environmental Health Resource Center –

Home –

Moisture Audit of Residential Structures –

New England Asthma Regional Council –