There was a home on Clearwater Beach, it’s a $2-million home, and this was three/four years ago, so I don’t know what it is now. But it was massive. And it was beautiful.
“And it was, believe it or not, the vacation home. And the woman of the house had a—she would go to antique shops and she bought this one cowhide footstool, right.
“It was a cowhide footstool, and she put it in the closet which was the size of a room for many people, and 2½ months later comes back, and there is mold all over the house, and they’re trying to figure out what happened.
“Yes, you can cross-contaminate another place by bringing in [mold] spores.”
Mold Solutions CEO & Founder, Brandon Faust, February 1, 2024
“Well, you go into the closet and the closet was Ground Zero.
“It was like a full mold-bloom in that particular closet. So the mold spores actually came from the footstool, and then because of the HVAC being on but not functioning correctly—it was on but it was not pulling water out of the air, so it was fast-cooling; flash-cooling is what it’s called—where the HVAC was too large for the home, so it would cool it off too rapidly and not pull enough water out of the air.
“So it remained humid, and there was enough water that the spores on the footstool had a perfect environment and completely took off.
“So the answer is, yes, you can cross-contaminate another place by bringing in spores, and if the climate and the environment is good or right for that particular scenario, yes, you could wind up with cross-contaminating and a full mold bloom.”
The Science Behind this Story
Two separate and important concepts are at play here:
- First, cross-contamination presumably occurred when an old or pre-owned piece of furniture was brought into a new/different home.
- Second, “short-cycling” of an A/C system contributed to elevated home humidity, which also contributed to mold growth.
We’ll examine each of these separately.
Cross-Contamination:
Items and belongings that are moldy can carry mold spores to a new location if moved. A cowhide footstool is a plush item whose depth and fabric makes it difficult if not impossible to fully rid of mold spores, which mostly range in size from 2-20 microns (35 mold spores fitting across the width of a human hair). This footstool was also old or pre-owned, and may have come from a moldy home. Perhaps the spores were dormant.
Cross-contamination of mold spores is a widely-acknowledged phenomena, though it has spawned two opposite schools of thought—one being “throw everything moldy away,” the other being “throw nothing moldy away; just clean it.” In this case, we know the new home was located near the beach (high-moisture), in Florida (high humidity), that the footstool was placed in a closet (air flow?), and that the homeowner was away for 2½ months. These conditions all imply limited air flow, and increased moisture or humidity, both of which contribute to mold growth.
And while we’re discussing cross-contamination and tracking in mold spores from outside, there is also its opposite: Unoccupied homes—like vacation properties for Snowbirds in Florida—can get moldy or mildewy in part because no one is at home doing homely things like adjusting temperatures, running ceiling fans, and moving about.
Short-Cycling:
Short-cycling is a technical HVAC condition that occurs when an A/C is either too large or too small for the house it was installed in. This causes a problem that can lead to mold growth, because your A/C doesn’t just cool your house—it also extracts moisture from the air. Your A/C is your home’s largest dehumidifier—if it is properly running, and correctly sized.
As a homeowner, you should know that if your A/C is constantly turning on, then off, on, then off—i.e. if its cooling cycles are short—then you may have an A/C sizing problem that could soon become a mold problem.
Short cycling can either occur due to an engineering mistake, or due to later changes made to the home’s exterior. For each A/C installed in a home, a “cooling load calculation” is done that considers numerous factors—How big is the house? How is it insulated? How many windows are there? How many floors? What direction does the house face? How many trees surround it? Etc, etc., etc. If an engineer miscalculated these factors, a too-large or too-small A/C unit would be fitted for the home. Or, if changes are made later to the home—like a couple of trees are cut down, or new windows are installed, new insulation is added, etc., etc.—then the once-accurate cooling load calculation can now be wrong, causing high-humidity, and eventual mold growth.
Related References & Resources
- “Throw away items that can’t be cleaned and dried.” – U.S. CDC, “Homeowner’s and Renter’s Guide to Mold Cleanup After Disasters,” November 14, 2022
- “Don’t spread mold. When you go into a moldy room take off your shoes before you walk through the rest of your house. If you can, change your clothes.” – U.S. CDC, “Reduce your Exposure to Mold in your Home,” November 14, 2022
- “…if the [A/C] system is too large or too small for the space it serves, the cooling system can create high humidity by cooling without removing water vapor.” – NC Dept. of Health & Human Services, “Conditions That Promote Mold Growth,” February 20, 2020.
- Learn what the CDC, NIH, Mayo Clinic and other reputable sources say about mold allergies.
- Learn more about how Florida’s humid atmosphere can contribute to mold growth.
- Story as recounted by IICRC & NORMI-Certified Mold Remediation Specialist Brandon Faust, on Feb. 1, 2024.
