Windows bring in natural light, provide insulation, and enhance the overall look of a home or business. However, a cracked window can quickly become a major nuisance, leading to safety concerns, energy inefficiency, and the potential need for a full window replacement. While some cracks may seem to appear out of nowhere, most result from a combination of environmental factors and structural stress. Understanding the most common causes of window breakage — and how to prevent them — can help homeowners and business owners protect their glass features for years to come.

Thermal Stress Cracks

One of the most common causes of a cracked window is thermal stress cracks, which occur when glass expands and contracts due to drastic temperature changes. A classic example of this is placing a hot dish directly on a cold glass table, causing a sudden break. Windows experience a similar effect when exposed to different temperatures across their surface.

For instance, if one part of a double-paned window is exposed to extreme sunlight the uneven expansion can create small thermal stress cracks near the edge of the window. Similarly, on a cold day, a very chilled glass surface with an imperfection can lead to breakage.

Prevention:

• Avoid sudden drastic temperature changes where possible during peak sunlight hours.
• Inspect windows for damage or flaws.
• Ensure heating and cooling vents are positioned away from windows.
• Choose insulated glass to help regulate indoor-outdoor temperature fluctuations.

Impact Breaks

Impact cracks occur when an object forcefully collides with a window, leading to an obvious broken window or a distinctive starburst pattern. These types of cracks can result from accidents like a stray baseball, a bird collision, or even heavy wind-blown debris.

The angle at which the object hits the glass matters — if it strikes at a perpendicular angle, the impact is more likely to result in total window breakage.

Prevention:

• Install exterior window protection, such as shutters or storm windows.
• Keep tree branches trimmed to prevent them from slamming into windows during storms.
• Educate children about playing safely away from glass features.

Pressure Cracks

While less common, pressure cracks can develop due to drastic pressure system changes. These fractures often appear in insulated glass windows and are more likely to occur in locations experiencing extreme shifts in elevation, such as mountain regions or areas near airports. 

These cracks are unique in appearance, often forming a clean, curving break from edge to edge. Unlike an impact crack, there’s no visible point of contact — just a mysterious split in the glass.

Prevention:

• Choose high-quality insulated glass that can withstand pressure differences.
• Be mindful of window location and window design.
• If replacing windows, work with a professional to ensure they’re suited for your climate.

Incorrect Installation

Windows need proper support to function effectively. While not as common on modern window systems, improper installation or incorrect installation can cause excess physical stress on the glass, leading to cracks over time. A window that isn’t level or is too tightly secured can create pressure points along the edge of the window, making it more likely to break.

Another common issue in older windows occurs when window frames are too rigid, preventing natural expansion and contraction. This structural tension can cause cracks to form, often in the corners of the glass.

Prevention:

• Always hire experienced professionals for glass replacement in Allentown, PA.
• Ensure the frame allows for minimal expansion and contraction to accommodate outdoor temperatures.
• Inspect new windows for signs of stress near the corners or edges.

Closing Windows Too Hard

Believe it or not, something as simple as shutting a window too forcefully can lead to window breakage. When a window shut is slammed, it can create vibrations that weaken the glass structure, particularly in older or already stressed windows. If there’s already a minor crack present, an abrupt impact can cause it to spread further.

Additionally, forcing a stuck window open or closed places excessive strain on the glass, making it susceptible to snapping.

Prevention:

• Gently close windows rather than slamming them.
• Check for obstructions before forcing a window shut.
• If a window is difficult to open or close, have it inspected for warping or frame misalignment.

What to Do If Your Window Cracks

If you discover a cracked window, it’s important to act quickly. First, carefully remove any remaining broken glass to prevent injury. While a temporary fix like tape or plastic sheeting can help in an emergency, it won’t provide long-term security or insulation. Instead, contact a professional for expert window replacement. 

At Alderfer Glass, we specialize in high-quality solutions for broken windows, from repairs to full glass replacement in Allentown, PA. Our experienced team ensures your windows are installed correctly and can handle even the most extreme weather without developing stress cracks or pressure problems. So don’t let a small window crack turn into a bigger problem. Contact us today to schedule your professional window assessment!