Preventing Mold in Your Home (2024)

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.

Is Your Home Mold-Friendly?

Without knowing it, many of us live in homes that are inviting to mold. In order to grow, mold requires:

• a food source (organic matter)
• moisture
• appropriate temperature
• oxygen

There are many materials in our homes that provide food for mold, such as wood, textiles, paper, leather, or surfaces covered with organic matter like dirt. The moisture in your home may be from a leak, flooding, or high humidity. You may not be able to control all of the food sources for mold, you can control the moisture.

Mold Prevention — Quick Facts

The best way to prevent mold is to control moisture.

1. Keep the indoor humidity below 60% relative humidity, ideally between 30% and 50%.
2. Repair leaky pipes and faucets.
3. Turn on the exhaust fans when bathing and cooking.
4. Clean out the gutters.
5. 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.

Decrease Sources of Moisture

Finding and fixing the causes of excess moisture in your home is one of the best ways to prevent mold growth. Use UGA Extension publication C1083, the Mold and Moisture Home Inspection Checklist to identify problem areas in your home. Some common sources of excess moisture include:

• leaky pipes and faucets.
• not using exhaust fans when bathing and cooking.
• air conditioning system flaws (oversized unit, duct leaks, dirty coils, condensation, etc.).
• clogged gutters and building leaks (roof, windows, etc.).
• poor water drainage around the house.

Check the Temperature

Temperature can impact the amount of moisture in the air. Condensation forms when a cold item comes into contact with warm, humid air. By increasing the temperature of cold items or surfaces you decrease the likelihood of condensation forming. Some ways to increase surface temperatures include:

• adding insulation to surfaces with cool temperatures.
• increasing the flow of heated air throughout the house.

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).

Improve Roof, Foundation, Siding and Window Flashing Systems

• When reroofing, upgrade to stronger synthetic underlayment and wind-rated shingles.
• Protect foundations and raised floors from moisture. Learn more from reliable sources such as the U.S. Department of Energy Building America Solution Center.
• Install a weather barrier material and drainage gap behind siding.
• Ensure proper installation of flashing around windows and other wall penetrations, especially at bottom corners. Use a “shingle fashion” layering system.

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.

Summary

Preventing mold in your home is easier than removing it. By preventing the moisture problems that can cause mold to grow, you are protecting yourself and your family from the health and property damage caused by this invasive and unwanted houseguest. Keeping your home dry is one of eight ways you can keep your home healthy. To learn more go to healthyhomes.uga.edu

8 Ways to Keep Your Home Healthy

Keep your home:

• dry
• pest-free
• clean
• contaminant-free
• safe
• ventilated
• maintained
• green and temperature controlled

For more information on rebuilding after a disaster, download the HUD Rebuild Healthy Homes Book or app: https://www.hud.gov/program_offces/healthy_homes/Post-Disaster-Resources

References

Turner, P. R., & Bailey, L. (2023). Mold and moisture home inspection checklist (Publication No. C 1083). UGA Cooperative Extension. https://extension.uga.edu/publications/detail.html?number=C1083

U.S. Department of Housing and Urban Development (2015, May). Rebuild healthy homes. https://www.hud.gov/program_offices/healthy_homes/disasterrecovery

U.S. Environmental Protection Agency. (2022, October 12). Mold. https://www.epa.gov/mold

U.S. Environmental Protection Agency (2008, September). Mold remediation in schools and commercial buildings (EPA 402-K-01-001). https://www.epa.gov/mold/printable-version-mold-remediation-schools-and-commercial-buildings

Reviewers

Dr. Sarah Kirby, Professor and Department Extension Leader, North Carolina State University

Dr. Claudette Hanks Reichel, Professor and Extension Housing Specialist, Louisiana State University Agricultural Center

Ms. Laura T. Smith, Telfair County Extension Coordinator, University of Georgia

Status and Revision History
Published on Dec 16, 2003
Published with Full Review on May 01, 2014
Published with Major Revisions on Mar 09, 2018
Published with Full Review on Mar 01, 2023