Is it Mold or Mildew?


Many people commonly refer to various building molds found in the Chicago area as “mildew”, and numerous mold cleanup products use the words “mildew” or “mildewcide” in their name and instructions. Although interchanging the words mold and mildew is acceptable by many, what’s the truth of the matter?

What is Mold?

According to the Center For Disease Control And Prevention (CDC), Mold is very common. It’s found both outdoors and indoors. No one knows exactly how many mold species exist, but it is estimated to exceed over 300,000 strains

Mold is a distinct species and genus within the fungi family. (Did you flashback to biology class?) It’s one of the main decomposition methods that nature utilizes. Molds or fungus feed upon dead and decaying organic matter, and so they enhance the decaying processes of nature on fallen trees, plants, dead animals, leaves, etc.

Without life forms like mold, your Chicagoland property would be buried under piles of dead stuff. So that’s great. But problems arise because mold doesn’t know the difference between dead trees in the forest and a wet wall stud in a home. And since mold spores are always floating around, they easily find what they need to grow and reproduce; food, moisture, and darkness.

Mold can also grow on many nonporous materials such as concrete and brick. And with the right temperature, moisture, and food, mold will grow almost anywhere. A rolling stone may gather no moss, but one sitting still sure can. Although it’s more prevalent and grows more quickly on porous surfaces like drywall and wood (because there’s more food), over time even a large area of concrete or brick can be covered by it. This is especially true in high humidity when the temperature between the surface and the air is slightly different.

What is Mildew?

Mildew is likewise a segment of the fungi family, but a different genus. Mycologists (those who study the branch of botany dealing with fungi) regard it as a parasite because it feeds only on living plants. They’re divided into two sub-groups:

  1. Oidium-Erysiphe, familiarly named Powdery Mildew
  2. Peronosporaceae, familiarly named Downy Mildew

These take the form of a white or gray powdery or splotchy deposit on plant leaves and stems and are often caused by poor air circulation within or around the plant, and dampness or high humidity. And that’s an important distinction because most buildings will never have a mildew infestation unless they’re growing a ton of plants inside. But since the majority don’t mildew is rarely an issue with indoor contamination.

Many times, the term mildew will be used generically to refer to mold growth that has a flat growth tendency. In other words, it doesn’t grow roots and thus it’s non-destructive and easily scrubbed away. It, too, will grow anywhere there’s enough moisture, such as bathroom sinks and showers, basement walls, or fabrics.

For these reasons, a mold expert or a home inspector should never lump mold and mildew together or say that they’ve found mildew growing in or on a building.

Get the Remediation Help You Need

If you have a Mold Growth — or suspect you do —contact Chicagoland’s premier mold remediation services company ServiceMaster Restoration by Simons. Our mold removal specialists have the knowledge, equipment, and products to get rid of this potentially dangerous invader.


About Us: ServiceMaster Restoration By Simons, is a SB100 Best of Small Business Award Winner 2021, Bronze Stevie® Award in the Female Entrepreneur of the Year category in the 18th annual Stevie Awards for Women in Business, recipient of the 2020 Better Business Bureau’s Torch Award for Marketplace Ethics, and recipient of the 2020 Skokie Business of the Year Award, Honorable Mention Category. ServiceMaster Restoration By Simons (MBE/WBE) is a family operated, IICRC & OSHA Certified company serving Chicago, Oak Park, River Forest, and the North Shore. We provide commercial disaster restoration services including Water & Flood Damage Restoration, Fire & Smoke Damage Restoration, Mold Remediation and a wide range of interior specialty cleaning including COVID-19 Cleaning Services, Hoarder & Clutter Cleaning, Post-Construction Cleaning, Carpet & Upholstery Cleaning to residential and commercial customers. For more information, call 773-839-5542 or visit or


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