Mold Statistics (2023)

Mold Statistics

Hidden in the shadows of our homes, mold and its toxic byproducts, mycotoxins can have serious health consequences. In this article, part of our series on real estate facts and figures, we'll present key mold statistics that highlight its prevalence and potential dangers.

Key Stats

  • Mold is common in 47% of residential buildings in the United States.

Percent of US Residences That Have Mold

  • The cost of mold remediation ranges from $1,373 to $3,325, with an average expense of $2,347.
  • 21% of asthma cases in the U.S. could be linked to dampness and mold.
  • Mold-related infections have an economic impact of $5.6 billion annually in the U.S. while asthma adds another $16.8 billion.
  • Home resale values can drop 20-37% due to mold issues.

How Many Homes Have Mold?

There is always a little mold everywhere, whether in the air or on surfaces. Mold only becomes a problem in a home when the concentration of spores is greater than what is found outside.

The National Institute for Occupational Safety and Health estimates based on an analysis of several studies that 47% of residential buildings in the U.S. have visible mold or mold odor.

Water damage is a leading cause of mold in buildings. Here are a few more stats that can shed some light on the prevalence of dampness and mold in the U.S.

  • 30% of schools in the U.S. have plumbing problems.
  • 27% of schools have roofing problems that could lead to interior or exterior water leakage.
  • 85% of commercial office buildings have experienced water damage in the past.
  • 45% of office buildings have current leakage problems.

What Causes Mold in A House?

Mold in a house is typically caused by excess moisture or humidity. Some common sources of moisture that can lead to mold growth include:

  • Water leaks from pipes, roofs, or windows.
  • Flooding or water intrusion from heavy rain or storms.
  • High indoor humidity, especially in areas with poor ventilation.
  • Condensation on cold surfaces like windows and walls.
  • Dampness in basements, crawl spaces, or attics.
  • Poorly maintained or malfunctioning HVAC systems.
  • Wet or damp materials, such as carpets, upholstery, or clothes.
  • Inadequate ventilation in bathrooms, kitchens, and laundry rooms.
  • Insufficient or improper insulation in walls or ceilings.
  • Building materials with high moisture content during construction.

If these sources of moisture are not addressed promptly, mold spores present in the indoor environment can settle and start to grow on surfaces, leading to mold infestations. To prevent mold growth, it's essential to control moisture levels and address any water issues in the house promptly.

How Does Mold Affect Health?

Mold can have various effects on people, and the extent of the impact depends on factors such as the type of mold, the individual's sensitivity, and the amount of exposure. Some common ways mold affects people include:

  • Respiratory Issues: Inhalation of mold spores can trigger respiratory problems, especially in individuals with allergies or asthma. It may cause symptoms like coughing, wheezing, shortness of breath, and nasal congestion. In fact, 96% of people with chronic sinus infections got them as a result of overexposure to mold. (Mayo Clinic)
  • Allergic Reactions: Mold can induce allergic reactions in sensitive individuals, leading to symptoms such as sneezing, runny or stuffy nose, itchy or watery eyes, and skin rashes.
  • Irritation: Mold exposure can irritate the skin, eyes, throat, and lungs, causing discomfort and potential inflammation.
  • Aggravation of Existing Conditions: For those with pre-existing respiratory conditions or immune system disorders, exposure to mold can worsen their symptoms or lead to more severe health issues.
  • Systemic Effects: In rare cases, exposure to mold and mycotoxins has been associated with more severe health effects, such as fatigue, headaches, cognitive difficulties, and immune system suppression.

Mold & Asthma

Studies have revealed a clear link between damp buildings and asthma symptoms in individuals who already have asthma. Additionally, there is evidence suggesting that damp buildings can also contribute to the development of new-onset asthma in some cases. Here are some stats about the link between mold and asthma.

  • 21% of asthma cases in the U.S. could be linked to dampness and mold. (WHO)
  • Dampness and mold are associated with a 30-50% increase in rates of respiratory illnesses. (WHO)
  • About 4.6 million asthma cases in the U.S. are caused by mold. (EPA)
  • Removing mold from the home reduces asthma-related symptoms by 25-45%. (WHO)

Economic Impact of Mold

Mold can have various economic impacts, both direct and indirect, depending on the extent of the mold problem. Here are some of the economic impacts of mold in homes.

Property Damage and Remediation Costs

Mold growth can cause structural damage to buildings, homes, and other structures. The presence of mold can weaken materials, leading to the need for costly repairs and remediation efforts.

The cost of mold remediation typically falls within the range of $1,373 to $3,325, with an average expense of $2,347.

Here’s a breakdown of the cost you can expect for mold remediation depending on the extent of the mold problem.

Affected Area (SqFt)Cost Range
50 $500-$1,500
100 $1,000-$3,000
150 $1,500-$4,500
200 $2,000-$6,000
500 $5,000-$15,000
1,000 $10,000-$30,000

Health Care Costs

Exposure to mold can lead to health issues, especially for individuals with respiratory problems, allergies, or compromised immune systems. Increased healthcare expenses may result from treating mold-related illnesses.

  • Mold-related infections have an economic impact of $5.6 billion annually in the U.S. while asthma adds another $16.8 billion. (Journal of Environmental and Public Health)

Reduced Property Value

If mold is discovered in a property, its value can decrease significantly. Potential buyers or renters might be deterred from investing in or occupying a mold-affected property, leading to decreased demand and a decrease in property prices.

  • Home resale values can drop 20-37% due to mold issues. (Appraisal Journal)

Mold Prevention

Preventing mold in a home involves controlling moisture levels and maintaining a clean and dry environment. Here are some effective steps to prevent mold growth:

  • Fix Leaks: Repair any leaks in plumbing, roofs, or windows promptly. Even small leaks can lead to mold growth over time.
  • Reduce Humidity: Use dehumidifiers, especially in damp areas like basements and bathrooms, to keep humidity levels below 50%. Smart home moisture sensors can help.
  • Proper Ventilation: Ensure your home is well-ventilated, particularly in areas like bathrooms, kitchens, and laundry rooms. Use exhaust fans to remove moisture during and after activities that generate steam or humidity.
  • Use Mold-Resistant Products: Consider using mold-resistant paint and building materials, especially in areas prone to dampness, such as bathrooms and basements.
  • Keep the Home Clean: Regularly clean and dust your home to reduce the buildup of organic matter on which mold can grow. Pay attention to areas that are more susceptible to mold.
  • Control Condensation: Use insulation and ensure proper airflow to reduce condensation on cold surfaces, such as windows, walls, and floors.
  • Monitor Indoor Plants: Mold can grow in soil and on the surface of indoor plants. Keep an eye on your houseplants and avoid overwatering them.
  • Properly Dry Wet Areas: If an area gets wet due to spills or flooding, dry it thoroughly within 24-48 hours to prevent mold growth.
  • Use Exhaust Fans: When cooking or using the dishwasher, run exhaust fans to remove excess moisture from the air.
  • Keep Gutters Clean: Regularly clean and maintain gutters to prevent water from seeping into the walls and foundation.
  • Monitor and Repair Roofing: Check your roof regularly for any damage or leaks, and address any issues promptly.
  • Store Belongings Properly: Avoid storing damp or wet items in dark and poorly ventilated areas, such as basements or closets.
  • Use Air Purifiers: High-quality air purifiers with HEPA filters can help remove airborne mold spores and improve indoor air quality.

By following these preventive measures and promptly addressing any water-related issues, you can significantly reduce the risk of mold growth in your home. If you notice mold developing, take immediate steps to remediate it to prevent further spreading and potential health issues.


Mold is everywhere, but when it starts to build up in the home, it can lead to significant health and economic problems. However, with proper diligence, the risk of getting a mold problem can be greatly reduced.


National Institute for Occupational Safety and Health (NIOSH)

World Health Organization (WHO)

Journal of Environmental and Public Health

Centers for Disease Control & Prevention (CDC)

Mayo Clinic

The Appraisal Journal

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