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Thermal Stress Cracks in Windows: Prevention, Causes, and Solutions

5 min read

It’s a homeowner’s nightmare. You wake up, grab a cup of coffee and look out the window — and then you see the crack in your window’s glass. Now you need to look for a quick, temporary fix for it before getting on with your day. Curious what led to this unfortunate turn of events? Let’s discuss the most common reasons windows can crack and what you can do to deal with them.

What are Thermal Stress Cracks?

If the weather has been fluctuating between warm and cold, thermal stress cracks can form in your windows from the expanding and contracting of the glass. Stress cracks start small, usually on or near the edge of the window, and grow larger with exposure. Even if they’re fixed, over time, they can spread across the entire glass pane. We’d recommend a replacement window pane as soon as possible for this reason.

Thermal stress cracks can also occur if you use your heater or air conditioning to sharply counter outdoor temperatures. Pay attention to your windows in these conditions!

Identifying Stress Cracks in Your Windows

Stress cracks may begin small and unnoticeable but can quickly grow into a significant issue. Recognizing these early can prevent larger problems. A stress crack generally forms a curve or line on the glass surface and often appears without any impact.

Other Common Types of Window Cracks

Cracks from Projectiles

Whether it’s due to a rock or a baseball game gone wrong, projectiles can cause cracks and fractures in your windows. These cracks are tricky, since there’s usually some cleanup involved. Unlike stress cracks, windows can even break under the impact of whatever hits them. With this comes broken glass and no possibility of repair.

It’s best to leave cleanup to the professionals if there’s a significant amount of broken glass. You can, however, carefully sweep up large shards if you’re wearing proper footwear. Then, close the area off until professionals arrive if you have pets or children, to ensure they stay safe. You can also cover the affected window area with a trash bag to keep the outdoors at bay until a window specialist arrives.

Pressure Change Cracks

This type of crack is most often found in insulated or double-paned windows. It doesn’t have as easily identifiable a reason for causing window breakage as the other types. Pressure cracks can occur due to weather pressure changes or window installations at very high or low elevations. If the window’s insulation does not match up to the elevation levels outside, a crack will quickly form.

Besides being less visible than impact-related cracks, you can’t fix most pressure cracks. You’ll want to go ahead and get in touch for a window replacement as soon as possible to minimize potential damage.

How to Prevent and Address Window Cracks

Choosing the Right Windows

Opt for high-quality, durable, double-pane windows, designed to withstand local weather conditions and temperature changes.

Regular Maintenance and Inspections

Conduct regular checks for any signs of damage or potential weaknesses in your windows. Early detection is key to managing the costs and effects of window damage.

Professional Installation and Replacement

Ensure your windows are installed by certified professionals who can assess and adapt to local environmental conditions. If a thermal stress crack occurs, consider a full window replacement to ensure safety and efficiency.

Common Questions Regarding Window Cracks

What is a stress crack in a window?

A stress crack in a window is a crack that forms without direct impact, typically starting at the edge of the window pane. These cracks can be caused by thermal stress from abrupt temperature changes, physical stress from improper installation, or pressure differences.

What does a stress crack in a window look like?

Stress cracks usually appear as a thin, straight line that starts at the edge of the window pane. They can sometimes curve slightly and will gradually get longer over time if not addressed.

Are stress cracks in windows covered under warranty?

Coverage for stress cracks can vary depending on the manufacturer’s warranty. At Window World of Muscle Shoals, our warranty covers stress cracks under certain conditions. Please review our warranty details or contact us directly for specific information.

What causes thermal cracking in glass?

Thermal cracking occurs when there is a rapid temperature change that causes the glass to expand or contract quickly, leading to stress that fractures the glass. Common causes include direct sunlight heating the glass or cold air from air conditioning striking hot glass.

How do you prevent thermal stress cracks in windows?

To prevent thermal stress cracks, ensure your windows are of high quality and appropriate for your climate. Avoid drastic temperature changes near your windows, such as blasting hot air from a vent directly onto cold glass. Regular maintenance and inspections can also help identify risks before they cause damage.

How do you fix a thermal stress crack in a window?

Small thermal stress cracks can sometimes be temporarily managed with adhesive tapes or glass repair kits as a short-term solution. However, for a permanent fix and to ensure safety and efficiency, replacing the cracked pane or window is often necessary.

Can you fix a crack in a window without replacing it?

Minor cracks can sometimes be repaired using resin applied by a professional, but this is generally not advisable for larger or stress-related cracks. Replacement is often the safest and most long-term solution for severe damage.

What are the different types of window cracks?

Window cracks can be generally categorized as stress cracks, impact cracks, and pressure cracks. Stress cracks occur due to temperature changes, impact cracks result from something hitting the window, and pressure cracks can happen from environmental pressure changes or incorrect installation.

Why would a window crack from the inside?

A window might crack from the inside due to thermal stress, especially in double-pane windows where different temperatures affect each pane differently. Internal defects in the glass or significant pressure differences between the inside and outside environments can also lead to cracks.

Windows You Can Depend On

Even when cracks can get fixed or filled in, this may not offer the long-term results you need. If your windows are suffering from stress cracks, it’s time to consider high-quality replacement windows from Window World of Muscle Shoals. Made with durable double-paned glass and custom-built to fit your home’s specifications, they also come with quality service. Plus, Window World’s lifetime warranty ensures you’ll have help in the unlikely event they become damaged and need replacement. Contact us today for a free estimate on windows built to last!