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How to Remove and Prevent Black Mold on Windows

Every aspect of your home - every last inch - is a vital part of your investment as a whole. That’s why ensuring that everything is in pristine condition is a major part of your responsibility as a homeowner. Unfortunately, many of us take certain parts of our home for granted. For instance, while you might pick up on a leaky pipe almost instantly, blackened moldy windows might not pique your interest right off the bat. 

Even in the smallest amounts, mold isn’t something to be taken lightly. Known to cause breathing problems, eye irritation, rashes, and wheezing and coughing, mold can put your family in poor health if allowed to persist. 

So if you suspect that your windows might be the victim of mold, act fast. Here’s everything you need to know to keep that hazard from eating away at your home and your health.

How Does Mold Grow?

First things first - what causes mold to grow? There are a range of potential reasons, but the most common that might relate to your windows include: 

  • Moisture from humidity
  • Condensation
  • Water penetration
  • Prolonged periods of moisture 

Your windows are designed in such a way that they prevent moisture from entering your home. But in doing so, they become the first line of defense that gets exposed to these dangers. 

While it’s absolutely fine for your windows to get wet, it’s another thing for them to stay wet. Unfortunately, we’re not told to wipe our windows after a nice, long June shower. But leaving the moisture to stick around invites mold to grow. And all it takes is a single speck to kick off a full-blown infestation. 

As the mold thrives, people in and even around your home might experience serious symptoms that indicate a triggered allergic reaction. Individuals with asthma might also be severely affected by mold, calling for prompt resolve to prevent further health complications and dangers. 

Worst-case scenario, you’ll have to temporarily leave your home to let workers clear out mold that’s too extensively spread out. This is required to prevent any potential health hazards to occupants in your home and to other homes in the vicinity.

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How to Remove Mold From Windows

Now that we know how mold grows and why it’s dangerous, it’s time to talk about how to get rid of it. Fortunately, less pronounced cases of mold growth can be addressed DIY, allowing you to resolve the issue before you need to phone in the pros. 

To identify mold on your windows, try to keep an eye out for these red flags: 

  • Check for discoloration. Different types of mold tend to manifest varying colors. According to the CDC, the most common household molds include Cladosporium, Penicillium, Aspergillus, and Alternaria which tend to take on an olive-green to brown color. Other types, like the Stachybotrys atra takes on a darker blackish green color. 
    Discoloration can happen anywhere, but most typically develops around the lip of windows that swing open, or between the sash and the rail. Corners on your window frame might also give in to mold, especially if there’s a problem with your walls. 
  • If your colored windows make it a challenge to identify discoloration, you can test for mold by using a solution of diluted bleach. In a container, mix together 16 parts water with 1 part bleach. Take a clean cotton swab and rub the suspected mold in your bleach solution. 
    If the stain lightens but keeps coming back after you stop rubbing, then you can assume that it might be mold. If you want to be doubly sure, you can purchase a mold testing kit for better accuracy. 
  • While it isn’t recommended to go around sniffing to detect mold, you can assume that there might be a mold problem if you can smell it without trying. Usually, the odd smell will resemble that of an old book with a touch of mustiness.
    Try to leave your home for a while and leave it completely unattended for a few hours. Turn off air conditioning and close all your windows. Then, once your nose gets accustomed to the outdoors, step back inside. If mold is present, the smell should be more pronounced. 

Once you’ve confirmed the presence of mold, it’s time to get started on removing it. Keep in mind that mold removal isn’t something to be taken lightly. Failure to properly clean the mold could cause spores to spread through your home. When that happens, then mold can grow where the spores scatter. 

With that, it’s imperative that you’re prepared. Here are some essentials you’ll need before you get cleaning: 

  • Heavy duty cleaning gloves
  • Goggles/protective eyewear
  • N-95 respirator

If you can cover the surrounding areas in a tarp or newspapers that you can pick up and toss out after the process, then that would be ideal. Make sure you move away any furniture and decor before getting started to minimize the surfaces the spores can cling to. 

Spray the Affected Area 

The first thing you’ll want to do is to spray the affected area with some warm water. While you might be thinking that’s counterintuitive since mold thrives in moist areas, the purpose of spraying is to keep spores from flying around. Use a spray bottle to drench the window and any neighboring surfaces with warm water. 

Wipe Away the Mold 

Once everything is sufficiently damp, take some dishwashing liquid and dilute in equal parts warm water. Sprinkle the solution on the surface and use a paper towel or a textured rag to wipe away the mold. Closely inspect the mold’s behavior. Often, it will fade for a second, making you think it’s been cleaned away. 

After wiping the surfaces, take a moment to observe the mold. If they reappear after fading, then you might have to exert a little more effort to clear them away. Use a scraper and gently scrape away the mold. Make sure to wipe the debris with a damp paper towel each time some mold comes off. 

Toss all the used paper towels or rags into a garbage bag and tie it securely. Any tools used during the process should be soaked in a strong bleach solution to kill off any spores. 

Soak the Area in Bleach 

Take a spray bottle and fill it with half water and half bleach. Then spray the solution generously over the areas that you worked on. Allow the solution to soak for a while to kill off remaining mold and spores. Wipe away the bleach with a rag and make sure to toss that out as well. 

Dry Everything Down 

With a clean rag, wipe down all the surfaces until everything is dry to touch. Open the window slightly to let a breeze in to help dry down excess moisture that your rag can’t dry up. If there isn’t a breeze to help speed up drying, take a fan and position it in front of the window. Of course, a hair dryer can also be a suitable alternative, especially since heat can help suppress the mold further. 

Keep in mind that the steps indicated above may work for typical PVC windows and some wooden windows. But for wood windows with mold that has seeped into the grain, then these steps might no longer be effective. 

For Wooden Windows 

In that case, you might have to sand the affected areas down to a bare finish. Then use oxalic acid to bleach the affected areas using a cotton swab or an old toothbrush. Once the affected area lightens in color, rinse the solution off with warm water. 

Let the area dry completely before restaining the wood. After the stain has dried, then you can apply your choice of varnish or urethane to get it to look like the rest of the surrounding wood.

Window Mold Prevention

There is no way to completely free your home from mold. So be prepared to face the potential for recurring infestation if you can’t properly prevent window mold from happening. So, how can you stop mold from recurring, especially on your windows? Try these tactics: 

  1. Improve ventilation - Mold on bathroom windows may indicate that there isn’t enough ventilation to allow air to enter and moisture to escape. Improve ventilation by adding a ceiling fan.
  2. Optimize your HVAC - Keeping things cooler prevents mold from thriving. Most types of mold grow in temperatures of 70 degrees Fahrenheit or higher, so lowering down your HVAC can suppress their proliferation.
  3. Check for leaks - Gaps between your windows and walls can cause moisture from rain and humidity to leak into the structure and build up unseen. If you see walls around your windows starting to darken and rot, there might be growing mold deep within. Call in the pros to have the necessary repairs performed.
  4. Use a dehumidifier - Dehumidification equipment for residential use help to reduce the moisture in your air. Have one operating in your space during moist seasons or keep one turned on at least 16 hours a day in rooms that are almost always moist like laundry rooms and bathrooms.
  5. Clean regularly - Cleaning your windows regularly prevents the fungus-like growth from thriving. Disinfect with bleach on a regular basis and dry down all accessible window surfaces on a routine schedule.

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Over to You

Moldy windows are more than just an aesthetic issue - they pose a risk to your structural integrity and your family’s health. To prevent the hazards that come hand in hand with this common household intruder, keep an eye on your windows. Nipping the issue at the bud can keep you from having to call in the pros, maintain your windows in pristine condition, and prevent dangers to your family’s health.


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