7 Reasons Why Your Windows Are Leaking

February 27, 2024

In residences where windows have been in use for over 30 years, encountering leaky windows is not uncommon. Whether due to wear and tear or subpar installation, having windows that leak can lead to various issues, including:

Air leakage affecting conditioned air.

Heat loss or undesirable heat infiltration.

Condensation on windowsills or floors.

Growth or proliferation of mold.

Water damage.

When dealing with leaking old windows, opting for replacement windows from a reputable manufacturer proves to be a cost-effective and enduring solution. Selecting a trusted manufacturer like Sean Doyle Windows + Doors ensures not only high-quality windows but also comes with a comprehensive warranty.

Before making the decision to invest in new windows, understanding the root causes of window leaks is crucial. This article delves into the most prevalent reasons behind leaky windows.

Let’s get started!

1. It’s Not a Leak, It’s Condensation

However, the type of window condensation often mistaken for a leak is the one on the interior. Contrary to appearances, this is NOT a clear sign of a window leak but rather indicates high humidity within your home.

During winter, condensation forms on the glass when it is cooler than the moist warm air in contact with it. As condensation accumulates, it can drip and collect on your window sill or trickle along the walls, resembling a window leak.

While interior window condensation doesn’t stem from leaking windows, persistent high humidity can lead to subsequent issues. Excessive humidity in your home may foster mold growth, cause wood to swell and warp, and expedite the corrosion of metallic components.

2. A Broken Window Seal

Not every type of condensation is problematic. In fact, condensation occurring on the exterior side of the window during the summer is an indication that the window effectively insulates your home.

However, the type of window condensation often confused with window leaks is interior condensation. Contrary to appearances, this is NOT a definite sign of a window leak but rather signals high humidity within your home.

During winter, condensation forms on the glass when it is cooler than the moist warm air touching it. As more condensation accumulates, it may drip and collect on your window sill or trickle along the walls, resembling a window leak.

While the root cause of interior window condensation is not leaking windows, prolonged high humidity can lead to subsequent issues. Excessive humidity in your home may foster mold growth, cause wood to swell and warp, and accelerate the corrosion of metallic components.

2. A Broken Window Seal

Through time, window seals can break. This is usually due to wear and tear. Broken window seals can be a result of the following:

• Cracked caulking; and/or
• Flattened or worn out weatherstripping.

Cracked caulking or failing weatherstripping can cause air leaks and heat loss. Furthermore, when such window seals are broken, they can allow rainwater to seep into the house. 

3. Inadequate Window Installation

Regardless of the quality of your replacement windows, correct installation is essential to prevent window leaks. Ensure that the contractor handling your window installation is adequately trained for the task.

With window companies such as Sean Doyle Windows + Doors, you don’t even have to search for a separate contractor to install your windows. We provide professional window installation services to ensure that you maximize the benefits of our energy-efficient windows.

4. Intricate Window Layouts Without The Right Protection

Various window styles exist, ranging from traditional to unconventional, such as specialty shaped windows, bay and bow windows, and tall windows. Despite their aesthetic and functional advantages, proper installation with appropriate sealants, flashings, or overhangs is crucial to prevent water penetration.

Given that these window styles are more exposed to the elements than standard windows, additional insulation and protection are necessary to prevent wind-driven rainwater from infiltrating.

5. Worn Out Glass Seal

Condensation becomes a concern when it accumulates between the panes of glass. This occurrence is common in multi-glazed windows and is a clear indicator of a broken seal. Double-glazed and triple-glazed windows typically feature a sealed glass unit, and if the seal is compromised, condensation may develop inside, suggesting potential air leaks.

Moreover, if between-pane condensation is coupled with small puddles forming at the base of the windowsill, it indicates that rainwater can penetrate through the broken seal. The only effective solution for this issue is to either replace the sealed glass unit or opt for replacement windows.

6. Poor Flash Installation

In certain instances, stains forming at the top of the window frame may not be indicative of window leaks but rather leaks in the wall arising from poorly installed flashing. To prevent water infiltration into the walls, a robust integration among the window, building paper, and flashing is essential.

Improperly installed or damaged flashing can lead to surface breaks, permitting water to seep through. Addressing this issue involves installing stretchable flashing as a single continuous piece, avoiding patches that create vulnerable points.

It’s crucial not to substitute window flashing material with building paper or house wrap. Using the appropriate material ensures superior water protection and minimizes the risk of damage caused by leaky windows.

7. No Paint Seal

The outer molding, responsible for securing the window, should be painted in a manner where the paint slightly extends onto the pane. While it might seem counterintuitive given efforts to avoid paint on the glass, adhering to this practice establishes a seamless paint membrane from the molding onto the pane, creating a waterproof seal to deter moisture penetration.

When All Else Fails, Call in the Pros

If you’re still wondering how to fix scratches on glass windows after trying all the DIY solutions we’ve listed, then it may be time to call Sean Doyle Windows & Doors.

For over four decades, we have been the trusted manufacturer of energy-efficient and long-lasting windows for numerous clients in Canada. With our premier collection of windows and doors, you never have to worry about your windows getting scratched up again.

‍Contact us today for a free estimate!