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How to Control and Stop Mould Growth on Windows

Window Mould Removal - How to

Mould growth on and around windows isn’t uncommon, in fact it’s one of the most common areas you’ll find mould. Although we rarely let it get out of hand as it’s in our view each day, it still makes an unsightly mess of our windows. We’ll go over what to do if you find window mould, as well as how to remove it and when to call a professional.

What Causes Window Mould?

Mould surrounding a window is typically caused by a buildup of dirt, dust and debris around the window. Air flow is blocked by this foreign matter allowing for a great surface for the mould to grow on. Mould rarely grows on the glass; however the caulking and sills tend to grow mould fairly easily. Once mould begins to grow, it eats away at the caulking and can damage or permanently stain it. Mould can also grow between the panes of glass, along the frame and tracks.

Mould requires moisture; it can get this food from the change in temperature between outdoors and indoors, excess humidity inside the building or a nearby leak.

Once mould begins to grow, it eats away at the caulking and can damage or permanently stain it.

Steps to Assessing and Removing Window Mould

1. What Should I Do if I Find Window Mould?

  • First, we need to assess the problem and find the cause:

Are there any leaks around the window? Is there adequate insulation? To assess these issues you may need to remove and maybe even replace the window. Consider bringing in a window specialist in this circumstance.

Is there adequate ventilation? Typically ducting vents are installed below windows, if there isn’t one you’ll want to increase the air flow to that area. A fan might work.

Check the roof and gutters. Are there any leaks coming from the roof? Are your gutters backed up?

  • Second, we need to assess how severe the mould growth is:

For mild cases, you can consider taking care of it yourself; using the appropriate tools it shouldn’t be too difficult to remove. Please move on to steps 2 and 3 for tips on how to remove the mould.

For severe cases where there is an excess build up, we’ll need to take a different approach. Removing mould can cause a release of mould spores into the air. Once this happens is when it becomes a more severe problem. Mould can cause adverse health effects, especially among those with respiratory illness such as asthma or those with allergies. Excess mould can still affect those without such illness as well. In more severe cases, it’s best to let a professional take care of the problem. As professionals, we use the proper tools and air purification to remove the problem effectively and safely ensuring it doesn’t affect the rest of the building.

2. How Can I Prevent Window Mould?

In order to prevent window mould, you’ll want to ensure the window, sills, trim and tracks get cleaned regularly. Here in Canada with our fluctuating temperatures, it’s not uncommon to experience window condensation. Showers and cooking can make this problem worse. If this happens in your home or building, try adding a fan to the area, if the extra air flow doesn’t work or if its winter, it may be better to use a dehumidifier. These will help draw the humidity out of the air and keep moisture off the windows. You’ll also want to ensure the windows are properly sealed and insulated. Have a professional installation technician take a look to ensure it’s sealed properly.

3. How to Remove Window Mould Safely?

In mild cases, simply using a detergent or bleach to remove the mould is effective. Ensure you have adequate rags and a spray bottle with the detergent mixture. You’ll also want a soft scrub brush and Q-tips to get into tight areas around the tracks and corners.

For severe cases, you would need adequate air purification, containment, respirators and proper PPE, again it’s best to leave these more severe cases to the professionals.


Mould growth on and around windows is unsightly but very common, follow these steps and you’ll stop any issues before they begin. If you want more information or an assessment on your issues, contact your local remediation specialist.

If you’re in the Winnipeg and surrounding areas, we can help! Contact us today at

1-833-367-7354 or visit our contact page HERE.


Q: Do you find you often have issues with window mould? What steps did you take to prevent the issue? | Comment Below

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Keywords: Mould growth, stop mould growth, Remediation, Winnipeg,



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