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Article by Michael A / July 13th, 2022

How to Clean Mold from Window Sills

Your home is meant to be a safe haven where you can rest and relax after a long day. 

However, if your home becomes infested with mold, what once was a haven can quickly become a nightmare. Mold can have many negative impacts on your health and can even cause certain allergies and health conditions.

This article will discuss how to deal with moldy window sills, including what supplies you will need and the six key steps in the cleaning process.

Keep reading to learn all about cleaning up mold in your home and when to consider calling a professional mold removal service!

Why Preventing Mold Growth in Your Home is Important 

According to the U.S. Environmental Protection Agency (EPA), molds can produce an assortment of different substances including allergens, irritants, and even toxic substances like mycotoxins. 

The EPA further states:

Allergic reactions to mold are common. They can be immediate or delayed. Molds can also cause asthma attacks in people with asthma who are allergic to mold. In addition, mold exposure can irritate the eyes, skin, nose, throat, and lungs of both mold-allergic and non-allergic people.”

Keeping this in mind, it is of the utmost importance to keep your home free and clear of mold. 

When it comes to searching for mold in your home, your areas of focus should be anywhere that gathers moisture, such as damp basements or windows. Mold is particularly common around window sills, as there are often small cracks and crevices that retain moisture and make the perfect mold breeding ground.

If you are dealing with mold growth on your window sills, then this guide is meant for you. Let’s first dive into what supplies you need to clean up mold from around your windows. 

Supplies Needed to Clean Mold

When dealing with mold in your home, it is important to use good safety practices and quality supplies to ensure your health is not at risk.

Here are the key supplies needed to clean mold: 

  • Bleach: If the build-up of mold on your window sills is severe, you may need to douse it with a bleach spray to help loosen up mold in particularly tricky spots. Keep in mind that bleach is a corrosive chemical that can cause damage to wood, paint, and other materials commonly found in window sills, so you may need to retouch the paint or finish of your window sills after applying bleach. 
  • Gentle Detergent: For less severe cases of mold build-up, a gentle detergent such as dish detergent can help you clean up the mold. Additionally, you can also fill a spray bottle with 3% hydrogen peroxide to spray the area down after you cleaned it with detergent. Hydrogen peroxide has antifungal properties, making it a good choice for eliminating any remaining mold spores. 
  • Scrub Brush & Scraper: After you have applied your cleaning agent(s) to the mold, you will use a scrub brush to lift it all away from the surface of your window sills. Depending on the severity of the mold growth on your window sills, you may also need a heavier-duty scraper to peel away any mold or mildew that is stuck on. 
  • Goggles & Mask: Mold poses serious risks to your health, especially if you have asthma or severe allergies. As such, it is highly important to protect your eyes, mouth, and nose when working in close proximity to mold. For your mask, the best option is an N-95 respirator or a mask with similar protection. Moreover, any open wounds should be bandaged or covered, and you should minimize the amount of exposed skin you have as well.
  • Gloves: Along with wearing goggles and a mask, you also need to protect your hands with a sturdy pair of work gloves. Ideally, these gloves should be made from rubber so that they can be cleaned off and used again. Make sure to keep your hands away from your face and any uninfected areas so you do not spread mold spores elsewhere in your home. 
  • Trashbags: One of the most important supplies to have on hand is heavy-duty trash bags. As you remove the mold from the surface of your window sill, you need to dispose of it immediately and securely. A heavy-duty trash bag is the perfect option, as it will seal away the mold spores, making it safe to transport the bags from your home to a dumpster or garbage disposal center. 
  • Towels or Rags: While you will be using your scrub brush to loosen and lift the mold, you will also need paper towels or rags to clean the loose mold up. Using rags or bathroom towels is a less wasteful option than using paper towels. However, you will need to clean these rags and towels thoroughly afterward if you plan on ever using them again. 

Once you have all of your supplies gathered, it is important to set up a cleaning area and a non-cleaning area. In your cleaning area, lay out towels or a protective tarp to catch any falling mold. You will also place your trash bags and other supplies here as well.

This cleaning area should be a small portion of your home at a time, with a non-cleaning area set up nearby. In this area, you can keep your phone, a covered drink, snacks, or anything else you might need that is not an essential supply.

Whenever you take a break and visit this non-cleaning area, make sure to first remove any contaminated clothing or gear so as not to spread the spores. 

6 Steps for Cleaning Mold Off a Window Sill

With your supplies gathered and all of the moldy spots on your window identified, it is finally time to start the cleaning process.

Here are 6 steps for cleaning mold off a window sill: 

1. Put on Safety Gear

Before coming close to the mold, your first crucial step is to put on all your safety gear. Per the supply list above, this should include rubber gloves, goggles, and a quality mask. 

Keeping this safety gear on at all times while you are cleaning up the mold is paramount. Coming in too close of contact with mold can cause allergic reactions and even sometimes longer-lasting health complications and a greater sensitivity to existing allergies. 

When you are ready to exit the cleaning area, it is important to remove all of your safety gear and place it to the side. This will prevent any wayward spores from finding their way into different areas of your home. In this same vein, it is recommended to keep fans and AC units off or on low to keep mold spores from being blown into another room or uncontaminated area.  

After you have completed your cleaning process, make sure to also clean off your safety gear and store it in a dry location. Spraying your gear with either a bleach solution or hydrogen peroxide should be sufficient for killing off any remaining spores. 

2. Place a Drop Sheet 

Just as you need safety gear to protect your skin, eyes, and mouth, your home also needs a protective layer as well — especially if the floor below your window sill is carpet. 

Placing either a drop sheet or several towels below the area where you are cleaning allows you to catch any falling mold and prevent it from contaminating your home further. A drop sheet also helps ensure that no drips of bleach or cleaning solution end up discoloring patches of your floor. 

Drop sheets are pretty easy to come by and you can typically find one at your local hardware store or supermarket. Some drop sheets are reusable, so make sure to check the packaging for reuse and cleaning instructions.

Since this drop sheet is likely to come into contact with quite a bit of mold, we recommend adding a small amount of diluted bleach to your washer if you plan on washing and keeping the drop sheet. 

3. Mix Your Cleaning Solution

When cleaning up mold on your window sill, there are 3 main cleaning products you can use:

  • Bleach
  • 3% Hydrogen Peroxide
  • Gentle Detergent

While hydrogen peroxide can generally be applied directly to your window sill without any dilution, both bleach and detergents should be mixed with water before applying. 

If you are using bleach for the purpose of killing mold, the CDC recommends mixing one cup of bleach for every one gallon of water. The CDC also stresses that you should not exceed this bleach-to-water ratio, as bleach is a powerful chemical, and to dry surfaces “quickly and thoroughly” after cleaning. 

As for gentle detergent, it is important to first note that a detergent typically cannot kill mold but can clean and remove it from a surface. The most common detergent used for this purpose is either dish soap (Dawn is a popular brand) or dish detergent. 

Both dish soap and dish detergent are potent substances, so it only takes a few drops added to a gallon of water to make this solution effective. The water in this solution should be hot, as this helps to loosen the mold and allow the detergent to work its magic.

4. Scrub the Window Sill

With your cleaning solutions ready to go, you can now begin the scrubbing and scraping process.

In an ideal world, you would be able to remove the mold from your window sill without damaging the paint or surface material underneath. However, removing all of the mold is much more important than maintaining the quality of the surface finishing.

If you do end up damaging the paint or surface material, your best plan of action is to either match the paint and repaint it or sand and revarnish it for wood surfaces. For anyone renting a home, you can also contact your landlord about the mold and have them help deal with it. 

As for the actual scrubbing process, we recommend using both a diluted bleach solution and a detergent solution to remove the mold. 

The bleach solution can be poured into a spray bottle to make it easy to apply. After applying, the bleach will need some time to set in — roughly 15 minutes generally. Once you have given the mold time to begin killing the mold and spores, you can then go in with your detergent solution. 

You will likely need a greater amount of the detergent solution than the bleach solution, as you will apply a more generous amount of the detergent to help clean up both the mold and the bleach. 

For easy access, keep the detergent solution in a bucket and grab a sponge to easily squeeze the solution on to the moldy areas of your window sill. 

5. Wipe Away Cleaning Solution

After applying your cleaning solutions and scrubbing away all the mold with your scrub brush, it is now time to dry and wipe off the clean window sill. 

Cleaning the window sill quickly and thoroughly helps ensure the area is not left with any remaining moisture where a stray spore could find a new home. Additionally, once the window sill is dried, you can spray a final layer of hydrogen peroxide to take care of any rogue spores and allow that to window dry.

If you are using paper towels to wipe up your cleaning mess, make sure to toss them in your trash bags immediately. On the other hand, if you are using reusable towels or rags, make sure to bring them to your washing machine directly after use. Wash with diluted bleach or a laundry detergent that contains bleach (and avoid using any towels you don’t want to be discolored!). 

6. Dispose of Dirty Supplies

With your window sills clean and fresh, the last step in this cleaning process is to properly dispose of or clean all of your supplies.

Items like your safety gear, the drop sheet, and towels are generally all reusable items — just make sure you clean them off thoroughly and according to the washing instructions provided with the products.

As for all of your disposable items (mold-covered paper towels, soiled scrub brushes, etc.), place all of these items in your heavy-duty trash bags and tie them off securely. In most places, mold can be disposed of just like regular waste, meaning you can bring it to the nearest dumpster or trash disposal center. 

Final Thoughts: When to Call a Professional Mold Removal Service

Cleaning up moldy window sills can be a real hassle, especially if you have existing allergies or health conditions. For greater convenience, safety, and thoroughness, it is a smart idea to call a professional home maintenance company for mold removal services. 

Here at Advantage Pro Services, we provide the Houston area with top-notch window cleaning services. Along with making both your interior and exterior window panels sparkle, we always make sure to clean your window sills and screens during every service as well. We hope this guide has helped you on your quest to remove mold from your home. If you live in the Houston area, give our team a call for a free quote!

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