What is Mildew?
Mildew is a form of fungus. It is distinguished from its closely related counterpart, mold, largely by its color: molds appear in shades of black, blue, red, and green, whereas mildew is white.
Mildew is commonly associated with damp cloth, fibers, leather goods, and several plant diseases (downy mildew and powdery mildew). Mildew-causing fungi use these substances as sources of food for growth and reproduction. Mildew often produces a distinctive smell.
The terms mold and mildew are sometimes used interchangeably. Although mildew can cause respiratory irritation in sensitive individuals, household molds, such as those from indoor water damage, are generally associated with more serious health effects.
In Old English, mildew meant honeydew (a substance secreted by aphids on leaves, formerly thought to distill from the air like dew), and later came to mean mold or fungus. Mildew grows on a damp cloth, leather, or on plants, and growing on leaves can damage the plant.
It appears as a thin, superficial growth consisting of minute hyphae (fungal filaments) produced especially on living plants or organic matter such as wood, paper, or leather. Both mold and mildew produce distinct offensive odors, and both have been identified as the cause of certain human ailments.
In horticulture, mildew is either species of fungus in the order Erysiphales or fungus-like organisms in the family Peronosporaceae. It is also used more generally to mean mold growth.
What Causes Mildew?
Mildew can grow on any organic matter, including the wood, wall, and wallpaper, and is caused by humidity and moisture. During the damp winter months, when the heating goes full blast and the windows stay shut, mildew can flourish and, as the weather warms up, humidity can help the process along.
Mildew requires certain factors to develop. Without any one of these, it cannot reproduce and grow. The requirements are as follows.
- A food source (any organic material),
- Sufficient ambient moisture (a relative humidity of between 62 to 93%), and
- Reasonable warmth (77 °F (25 °C) to 88 °F (31 °C) is optimal, but some growth can occur anywhere between freezing and 95 °F (35 °C)).
- Slightly acidic conditions are also preferred.
At warmer temperatures, the air is able to hold a greater volume of water; as air temperatures drop, so does the ability of air to hold moisture, which then tends to condense on cool surfaces. This can work to bring moisture onto surfaces where mildew is then likely to grow (such as an exterior wall).
How can mildew affect your health?
While mildew is mostly known for its negative effect on plants and crops when it grows outdoors, it may also impact your health (the same as mold) if you breathe in the spores. The same potential health issues exist with mildew as they do with mold. Some of these symptoms according to FEMA include respiratory issues like wheezing, nasal and sinus congestion, eye, nose, or throat irritation, and headaches.
If mildew is not removed, it will continue to grow and these symptoms may become worse. If you or someone in your household is experiencing these symptoms and is sensitive to mold, it is a good idea to inspect your home to find any problem areas.
How to Prevent Mildew?
- Add a dehumidifier to your home. It’s best to keep indoor humidity levels between 30-50% to stop build-up. Check out our recommendations.
- Avoid storing linens, books, or furniture in your basement or attic if they’re known to get damp.
- Always open the bathroom door after showering to allow moisture out.
- Seal bathroom grout lines every year if you have tiling. This will help waterproof your tub.
Preventing the growth of mildew, therefore, requires a balance between moisture and temperature. This can be achieved by minimizing the moisture available in the air.
Air temperatures at or below 70 °F (21 °C) will inhibit growth, but only if the relative humidity is low enough to prevent water condensation (i.e., the dew point is not reached).
With warmer temperatures, the water holding capacity of the air increases. This means that if the amount of water vapor in the warming air remains the same, the air will become drier (i.e. it has a lower relative humidity).
This again inhibits fungal growth. Warm, growth-favoring temperatures coupled with high relative humidity, however, will set the stage for mildew growth.
Air conditioners are one effective tool for removing moisture and heat from otherwise humid warm air. The coils of an air conditioner cause moisture in the air to condense on them, eventually losing this excess moisture through a drain and placing it back into the environment.
They can also inhibit mildew growth by lowering indoor temperatures. In order for them to be effective, air conditioners must recirculate the existing indoor air and not be exposed to the warm, humid outside air.
Some energy-efficient air conditioners may cool a room so quickly that they do not have an opportunity to also effectively collect and drain significant ambient water vapor.
FAQ
What Is Mildew?
Mildew is a form of fungus. It is distinguished from its closely related counterpart, mold, largely by its color: molds appear in shades of black, blue, red, and green, whereas mildew is white.
Where does mildew grow in a home?
Most often, you can find mildew on window sills and shower walls, to name a couple of places wherever moisture levels are high. It needs the same elements mold needs to grow warmth, darkness, oxygen, and moisture. When these conditions are present, mildew can readily grow on a surface.
How to identify mildew?
Mildew grows and spreads just as quickly as other molds, though the damage caused by it is usually cosmetic and can be treated without much trouble (more on how to treat mildew below). Sight and smell are still the two easiest ways to identify whether mildew is growing in your home.
What does mildew look like?
Mildew either has a powdery or downy texture. The powdery type of mildew is white when it first begins to grow but can turn yellow, black, or brown. Downy mildew starts out yellow and turns brown as it ages. Both types of mildew growth appear flat as they grow on flat surfaces.
What does mildew smell like?
Mildew, like other molds, has a musty smell that is caused by MVOCs. If your home smells musty, it could be mildew or other molds. You will have to visually confirm which one it is, or have a professional come to your home to test for both.
What causes mildew?
Mildew can grow on any organic matter, including the wood, wall, and wallpaper, and is caused by humidity and moisture. During the damp winter months, when the heating goes full blast and the windows stay shut, mildew can flourish – and, as the weather warms up, humidity can help the process along.
Is mildew harmful to your health?
While Mildew is not as dangerous to your health as certain types of toxic mold (black mold, for example), nor is it as damaging to your home, mildew should still be taken seriously and it’s important to remove it as quickly as possible in order to prevent adverse health effects and/or cosmetic damage to your home.
How do you stop mildew from spreading?
1. Keep Healthy Humidity Levels. Mold and mildew thrive in a humid environment, so it is important to keep your humidity levels down.
2. Fresh Air.
3. Use Green Cleaning Products.
4. Dry Wet Areas.
5. Keep Indoor Plants.
What is worse Mildew or Mold?
Without a doubt, mold is worse than mildew. According to American Home Shield, “the difference between mold and mildew is that, unlike mildew, certain types of toxic molds can result in serious health problems for you and your family.” Black mold, in particular, is dangerous for humans.
