That Black Stuff Around Your Windows May Be a Sign of a Bigger Problem

During one of my more recent deep cleaning sessions, I decided it was time to address all of the windows around my home. Wiping the glass down with some Windex has been part of my weekly cleaning routine for years, but I wanted to give the windows a good scrubbing, wash the curtains, and take care of any dust that may have built up around the sill.

Unfortunately, my cleaning spree uncovered a layer of mold and mildew around the edges of the windows that required a little extra work on my part. But the news wasn’t all bad, because mildew and mold around the window ledges isn’t always a sign of a bigger problem. Sometimes, this issue can have a fairly quick fix! 

The first thing you’ll need to keep in mind when dealing with this type of problem is whether you’re dealing with mold and mildew, or if it’s some other type of mess. In my case, I noticed that the black spots were indeed spots, which meant they were cropping up in small circles along the place where the top and bottom sash met on the interior of my window. 

If you’re seeing something similar — black or dark spots that have a distinctly circular pattern — chances are that you’re in the same boat. However, if you want to get a more definitive answer, you’ll need to call in a remediation expert or purchase a home testing kit. 

Mold is more than an eyesore, according to Jess Farinha, cleaning expert and founder of London House Cleaner, as it can also pose health risks for those with allergies or respiratory conditions. “You should definitely take safety precautions while cleaning,” she says, adding that you’ll need to wear the proper safety gear before getting started. 

“A mask, like an N-95 respirator, is non-negotiable,” she continues. “It does a great job of filtering out mold spores and preventing them from getting into your lungs.” Next, Farinha says that gloves will help protect your hands from both the mold and the cleaning agents you’re using to fight it. “You [should] also consider wearing goggles to protect your eyes from spores and splashes,” she adds.

Lastly, it’s all about the ventilation. “Open windows or use a fan to carry away spores from yourself and the indoor environment,” she says, suggesting that you keep this in mind if you are going to be whipping up a DIY cleaning concoction. “Mix your solutions in open space, to avoid inhaling fumes,” Farinha continues. “Also, wash your hands after you are done with cleaning even if you were wearing gloves. Your safety is paramount.”

Discovering mold anywhere in your home is nerve-wracking, but the good news is that when you find it around your windows, Farinha says it’s fairly easy to tackle. 

For the best results, you’ll need to give the windows a thorough scrubbing, which she says you can do using her go-to mix of equal parts water, baking soda, and liquid dish soap. “Adding dish soap will increase the cleaning ability of the solution,” she explains. 

Farinha says you should spray the solution on the affected area and let it sit for 20 to 25 minutes. Then, scrub it with a brush and sponge. Finally, wipe it away with a clean cloth.

To ensure that this doesn’t become an ongoing problem, Farinha says you’ll need to keep the area well-ventilated. “One of the best ways you can do this is by keeping your windows open all the time,” she says. “This will allow the fresh air to spread further into the room and keep humidity away.”

Also, frequent cleaning can help as well. “After you’ve tackled the mold that was growing, disinfecting the area is crucially important to prevent further growth and ensure it’s truly clean,” she explains, adding that a common kitchen ingredient works well for this part of the job. 

“White vinegar is a natural disinfectant that can kill most mold species,” Farinha says. “Simply fill a spray bottle with it, and spray generously on the affected areas, and let it sit for an hour.” She says that this will give the vinegar enough time to “penetrate and kill any lingering mold spores.” After that, you’ll want to wipe it away with a clean cloth and dry it thoroughly.

“The key to removing mold is not just removing what you see — it’s also removing what you can’t see, like the lingering mold spores,” she says, adding once again that maintaining good ventilation and keeping the area dry will go a long way in helping to prevent future mold growth. 

Depending on why you’re seeing mold and mildew, a good cleaning might not be all it takes to tackle this issue. “Mold around windows often results from moisture buildup, which can be due to poor sealing, condensation, or high indoor humidity levels,” says Jeramy Sibley, president of Glass Doctor, a Neighborly company. “To prevent mold growth, it’s important to check window seals regularly and address any maintenance needs as soon as possible.”

If the mold problem persists despite your cleaning efforts, or if you discover extensive mold growth inside the window tracks or on the walls surrounding the window, Sibley says it’s time to call a professional. “A pro can assess the situation, identify the root cause of the moisture problem, and provide a more permanent solution to prevent future mold growth.”

Fortunately for me, the issue in my home had to do with our windows not being closed all the way, which allowed moisture to build up where the windows weren’t sealed. However, for others, the fix might not be quite as easy, which is why it’s important to know when to call in a pro.

Looking to spring clean? Sign up for Apartment Therapy’s 10-day Spring Cleaning Cure, a free guided program that’ll bring you one step closer to a tidier home.