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Can mold growth in one location affect other areas?

Mold growth

Researchers at Yale University and the University of Tulsa recently conducted a study to see if mold growth in one section of a house can affect other areas of the home1. This is an interesting question, especially for people who have health issues which can be aggravated by mold growth.  Can mold in one level have a significant effect on another level of a house?

The Research Study

A two-story home was used for the study where mold was discovered in the basement after a flood.  Dust samples were taken off the door and window frames on various levels throughout the home. This was performed to see how far certain water damage indicating molds (such as Stachybotrys or Chaetomium) could travel.

Location, Location, Location

So what happens when mold growth is in the basement?  Could those spores reach the bedrooms on the second floor?  The study found that the greater the distance from the mold growth, the lesser the number of indoor spores.  In this case, mold spores decreased by 70% between the basement and the second floor. However, the study showed that some of these water damage indicating molds can still be found on the second floor.   How could the mold travel that far? By something called the “Stack Effect”.

Rising to the top

The stack effect is caused by warm air rising because it is less dense and more buoyant. Stack effect causes air to travel from the lower levels of the home to the upper levels, especially during cold weather. The pressurization can pull mold spores from the basement (or even a crawl space) into almost any area of the home.   

The results

The study revealed that mold spores are at a higher concentration when closest to the growth and weaken with greater distance.  The study mentioned that further research could be performed with properties that have forced air HVAC to see the effect that these systems can have in pulling spores through a house while in operation.  Interestingly, the house that was used for this study had a radiant heat system. It would have been interesting to see if the mold throughout the home would have been greater if the spores were sucked into a forced-air HVAC system and ductwork. 

Final thoughts: Can mold growth affect other areas of a house?

Although some of this has long been suspected in the air quality industry, there have been few quantitative studies on the distance that mold can travel throughout a home.  Can mold growth in one section of a house affect other areas? The study shows that mold in a basement can work its way into almost any indoor area of a home. This is important because basements are a common area of flooding and condensation issues and can greatly affect the health of the occupants. What happens in the basement doesn’t stay in the basement!

Mold testing by a professional can greatly aid in determining the extent of mold in a home, not to mention the underlying cause.   If you suspect mold but are unsure if you have it in your property, have an expert who is trained in finding moisture sources and hidden mold growth to prevent various health issues.

  1. https://pubs.acs.org/doi/10.1021/acs.estlett.9b00214

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”