Summer brings a blast of hot, humid weather, which provides the perfect conditions for so many fun outdoor activities: a fun pool party, a relaxing beach vacation... or unfortunately, a mildew infestation.
Because mildew is a type of surface fungus that pops up in warm, damp areas, it thrives during the summer months. And when your house is poorly ventilated, the flat, powdery growth decides to stay for a while. “What keeps mildew around is lingering moisture and unmanaged indoor relative humidity,” explains Michael Aughney, a microbiologist and owner of mold removal service Mold One. “If air isn't kept dry and moving, spores will continuously recolonize.”
Mildew doesn’t always show up in obvious places, either—it tends to settle in household spots that you wouldn’t normally think to check. If you’re worried that your home might be harboring this powdery fungus, we asked Aughney to identify the top places where mildew hides in hot summer weather. From damp corners to overlooked objects, these areas could use a thorough inspection. Ahead, Aughney also reveals the best ways to treat mildew and prevent it from resurfacing. So, grab your cleaning supplies and let’s wipe away the mystery of where mildew likes to fester.
Where Mildew Hides in Hot Weather
There are a few unexpected spots where mildew builds up around the house in the summer heat. Here are the biggest mildew hotspots to check—plus, the most effective way to treat each one:
HVAC Vents
When the weather heats up, your air conditioning system works overtime. As cold hair blasts through hot rooms, the contrasting temperatures interact with one another and leave behind condensation, which feeds mildew. “Cool conditioned air blowing through warm, humid rooms creates micro-condensation around register grates and inside ducts,” Aughney says. “If air filters aren't changed consistently, accumulated dust feeds dormant spores right at the air source.” To treat this mildew-infested area, turn off the power, remove the vent covers, and wash them in warm, soapy water. Changing the AC filter every month or two will prevent dust from trapping moisture.
Window Tracks and Sills
Just like indoor AC, hot and cold air mixing is also responsible for the buildup of mildew on your windows. “Warm summer humidity meeting cold AC glass creates heavy condensation pooling on sills, making it a top spot for hidden growth,” Aughney notes. When hot outdoor air meets the cold glass windows, condensation leaks—and the moisture just sits there. For freshly formed mildew, scrub the tracks with a mixture of one part white vinegar and one part water. Wiping down the stagnant water every week will also keep fungus at bay.
Washing Machine Seals
Because the rubber gaskets in your laundry machine work hard to prevent water leaks, they easily trap moisture, which gives musty-smelling mildew grounds to grow. “Front-load washers trap residual wash water and laundry debris in a warm, closed space,” Aughney explains. Luckily, cleaning the rubber gasket with a solution made with one tablespoon of bleach and one quart of water will remove the fresh mildew. To deter the fungus from returning, air out the washer door by leaving it wide open after every use.
Closet Corners
The hidden corners inside your closets offer the ideal home for mildew. That’s because these spaces are dark, damp, and still, so surface fungus tends to grow pretty aggressively. “Stagnant air in dark closets (especially on natural materials like leather shoes or fabrics) gives spores the quiet environment they need to multiply,” Aughney says. When humid indoor air gets trapped behind clothes or boxes that are piled up next to a cold exterior wall, mildew comes to life. After removing all the cluttered objects, scrub the affected corners with white vinegar, and let it air dry.
Crawl Spaces
Crawl spaces are other often-neglected household areas that are vulnerable to mildew. The foundation vents let in hot, humid summer air, which causes condensation to emerge on the cold floors. Protect yourself by strapping on a mask, goggles, and gloves before crawling into the contaminated space, applying a structural disinfectant to the wood joists and subflooring, and letting the solution dry out by using an industrial fan and dehumidifier.
How to Eliminate Summer Mildew
While we identified specific solutions for each aforementioned mildew hotspot, overall, eliminating mildew requires a two-pronged approach: treating the visible surface growth and the airborne microscopic spores, according to Aughney. Find out how to solve your mildew problem, depending on the severity:
Minor Mildew Growth
If you spot mildew on nonporous surfaces like glass, steel, or ceramic, scrub the infected spot with an EPA-registered fungicide, Aughney recommends. For porous surfaces like wood, fabric, or drywall, spray a hydrogen peroxide solution or white vinegar and wipe it away after letting the product sit for 15 minutes.
Widespread Mildew Issues
As for mildew infestations, you’ll need something more heavy-duty. “For persistent or widespread issues, professional dry-fog sterilants and antimicrobial treatments penetrate hidden nooks, wall cavities, and air spaces without requiring demolition,” Aughney says.
How to Prevent Summer Mildew from Growing Back
Prevention is the best solution to a mildew problem. Here are some of the most successful ways to keep mildew from resurfacing:
Regulate Indoor Humidity Levels
The ideal percent humidity for warding off mildew inside your house, according to Aughney, is 45 percent. Your HVAC system can help you regulate indoor humidity levels, but you can also use a residential dehumidifier.
Keep Dust at Bay
Because dust fuels microscopic spores, tackling your house’s dustiest hotspots will help manage mildew. “Keep surfaces well-dusted, vacuum regularly, and change HVAC air filters consistently, so spores lose their primary food source,” Aughney advises.
Manage HVAC Systems
To prevent season-specific mildew from taking over the hidden corners and crevices of your house, Aughney suggests getting your HVAC system serviced before intense midsummer heat. Cleaning your air ducts and turning on your exhaust fans whenever you’re showering or cooking will also impede mildew.
By treating visible mildew and actively discouraging it from coming back, you and your family will able to enjoy the indoor reprieve from the summer heat—without worrying about surface fungus.
Lilly Blomquist is the associate editor at The Pioneer Woman, where she writes lifestyle stories across a wide range of topics—including news, entertainment, holidays, food, and more.
