If you’ve just seen or smelled something that you believe indicates the possible presence of mold or mildew, you’re probably wondering which it is and what the difference is between the two.
Many people use the terms mold and mildew interchangeably and while they do share some things in common, they are two distinct phenomena.
Mold consists of organisms that have life but are neither plant nor animal.
All living things are part of one of five distinct kingdoms, which we will define here specifically in contrast to mold.
- Animal: Multi-celled, sexually reproductive, able to move on their own. Fish, birds, insects, etc.
- Plant: Immobile, cells of cellulose, oxygen-releasing. Trees, bushes, crops, etc.
- Fungi: Yeasts, molds, mushrooms, toadstools. Feed off of other living things, and they reproduce through spores.
- Protista: Organisms not deemed animal or plant, such as algae, and protozoa.
- Monera: Microscopic living things made single-cell organisms with no defined nucleus; bacteria.
Mold spores are part of the fungi kingdom. They get their nutrients from digesting organic material, effectively destroying it. What mold lives on is eventually broken down and caused to decompose.
Mold and mildew require water to survive.
To control moisture is to control both mold and mildew.
Ultraviolet light from the sun kills both mildew and mold.
The materials that mold digests include dead plants, dead trees, dead animals, and more.
Mildew refers to certain kinds of mold and fungus. It is technically mold that grows on a living plant, but is also defined as “mold in early stage” or the beginning of a mold colony.
“Mildew (mold in early stage) and molds grow on wood products, ceiling tiles, cardboard, wallpaper, carpets, drywall, fabric, plants, foods, insulation, decaying leaves and other organic materials.”Federal Emergency Management Agency (FEMA)
Mildew can be either “powdery” or “downy.” Powdery mildew affects flowering plants, beginning as white or gray speckles, which turn dark brown or black as it grows. Downy mildew starts yellow and turns brown.
If the factors causing it are left unchecked—moisture, humidity, darkness—mildew will be the beginning of a mold colony.
The following important similarities exist between mold and mildew:
- Both mold and mildew are everywhere, requiring only the right conditions for growth to begin becoming visible to the human eye.
- Both mold and mildew are forms of fungus. Both can be killed with fungicide, or relocated to an outdoor out-of-home environment where they no longer affect building occupants.
- Both mold and mildew require moisture in order to survive. Again, if you remove the source of water and moisture (whether it be a leaky roof or pipe, or the condensation from a hot shower), neither mold or mildew will be able to take root.
- Mold and mildew grow best in humid environments and can not survive at freezing temperatures.
- Mold and mildew also both spread through the dissemination of spores, which can travel on clothing and pets, in vehicles, or alone in the air.
- Attempting to prevent the travel of non-visible mildew or mold is futile, though care should certainly be taken after working with either mold or mildew to avoid spreading it.
- Both mildew and mold can develop within 24 hours of a “moisture intrusion event” that creates an ideal breeding ground.
The following important differences exist between mold and mildew:
- The easiest way to tell mold and mildew apart is by how they look.
- Mildew is usually white, gray, or yellow, and is fluffy or powdery.
- Mold is usually dark green or black and its texture is slimy or fuzzy.
- Mold can grow on both organic and inorganic material including paper, fabric, wood, and food.
- Mildew is unable to grow on synthetic or inorganic material such as plastic and metal.
“Molds can thrive on any organic matter, including clothing, leather, paper, and the ceilings, walls and floors of homes with moisture management problems. Mildew often lives on shower walls, windowsills, and other places where moisture levels are high.”United States Environmental Protection Agency (U.S. EPA)
- Mold has a higher vertical profile and projects itself off of the surface it lives on, even if ever so slightly.
- Mildew is typically flat, even with the surface it exists on.
“Mildew refers to certain kinds of mold or fungus. The term mildew is often used generically to refer to mold growth, usually with a flat growth habit.”U.S. EPA, “What is the difference between Mold and Mildew?“
- Mold is typically darker, whether a deep green, dark yellow-brown, or black.
- Mildew can start off white or light yellow, then turn gray, brown, or black.
- Mildew is unlikely to significantly damage the surface it rests on.
- Mold creates long lasting and significant damage to structures.
Ease of handling:
- Mildew is more easily cleaned up and gotten rid of.
- Mold removal may require the removal or repair of the surfaces it damaged.