Mold in your home is not only unsightly, it can also cause health problems. If you have mold growing in your home, you may experience allergy-like symptoms, asthma attacks, or other negative health effects. No one wants to live in a home with mold, but unless preventative steps are taken, mold can go from being an unwanted visitor in your home to a permanent resident.

Molds are fungi that reproduce by releasing spores into the air. Given the right conditions, the spores settle onto surfaces and begin to grow. They are a natural part of the environment. You can’t eliminate them, but you can prevent them from becoming a problem in your home.

The best way to prevent mold is to control moisture.

  • Keep the indoor humidity below 60% relative humidity, ideally between 30% and 50%.
  • Repair leaky pipes and faucets.
  • Turn on the exhaust fans when bathing and cooking.
  • Clean out the gutters.
  • Make sure water drains away from your home.

How Can You Control Moisture in Your Home?
It is important to maintain a moisture balance within the home. If your home is too dry, you may experience increased static electricity, dry skin, and dry nasal passages. If your home is too moist, mold growth may occur. Below are some tips to help maintain a moisture balance within your home. The EPA suggests keeping indoor humidity below 60% relative humidity, ideally between 30% and 50%. You can measure the relative humidity using an inexpensive moisture or humidity meter usually available where hardware is sold.

Prevent the Flow of Moisture
The movement of moisture in and out of your home may be contributing to increased moisture levels in your home. You can decrease the flow of moisture in and out of your home by:

  • Sealing air leaks around windows, doors, air register grilles, plumbing fixtures, and electrical outlets.
  • Sealing HVAC system air duct and return plenum leaks.
  • Installing vapor barriers in the crawl space.
  • Getting a home inspection to find and correct moisture problems.
  • Increase Air Circulation and Proper Ventilation
  • Air circulation and ventilation affect the amount of moisture in your home.

Things you can do to increase circulation and appropriate ventilation include:

  • Installing heating and cooling system vents and ceiling fans to improve circulation.
  • Using exhaust fans to remove excess moisture at the source and deposit it outdoors, such as the kitchen range hood, bathroom and clothes dryer exhausts.
  • Avoiding closing interior doors, unless there are return air grilles to allow air flow between spaces.
  • Putting vents in the attic. Vents should be located at the part of the roof that overhangs the walls (soffit) to allow in cooler air and also in the peak of the roof (ridge) to release warm air. Do not use powered attic vents since they may cause enough suction to pull conditioned air from the living space into the attic.
  • Checking to see if your crawl space is vented. If so, the vents should be located near each corner, within the top 8 in. of the foundation (in a flood zone, vents also are needed within a foot of the ground).

Control Household Humidity
Household activities can raise the humidity level in your home. These activities include bathing, cleaning, cooking, washing dishes, and washing or drying clothes. Reduce indoor humidity by:

  • Decreasing bathing time or reducing water temperature to minimize steam.
  • Turning on exhaust fans when cooking or bathing.
  • Washing only full laundry and dishwasher loads.
  • Venting appliances to the outdoors (such as your dryer and range hood).
  • Opening windows for increased air circulation (only when the relative humidity level outdoors is low—below 50%).
  • Using a dehumidifier (make sure you clean it regularly).
  • Using a well maintained, right-sized air conditioner on the “auto fan” setting (using the constant fan setting will return moisture to the home).

Manage External Water
Proper drainage around the house is an important part of preventing moisture problems inside. Ideally, homes should be built on the top of a hill so water drains away from the foundation. Unfortunately, many homes are either built into the side of a slope or on a flat site. These designs can lead to drainage problems. Over time you may have soil erosion and landscaping changes that shift drainage towards the foundation.

To prevent problems:

  • Create a 5% grade that slopes away from your home on all sides. It should go out a minimum of 10 ft.
  • Clean the gutters and downspouts regularly so they direct the water away from the foundation.

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