Glass Cracks

Why Did My New Window Crack?

So you've noticed that one of the windows in your home has a long crack running across it on the inside of your house, but the cause of the damage isn't apparent, so what happened? ... Cracks in a new window can be extremely frustrating. After all you just had them installed. So what happened and what should you do?

Why New Windows Crack

Understanding stress cracks: There is a scientific reason for the crack that has suddenly appeared on your window. Thermal stress cracks, or "stress cracks" as they're more commonly known-Typically occur in windows when a thermal gradient causes different parts of the glass to expand by different amounts. At some point, the stress of the expansion may overcome the strength of the glass, causing a crack to form.

Here's a simpler way of looking at it: Stress cracks in windows are similar to what might happen if you poured ice cold water into a hot glass baking dish that you just took out of the oven. As the cold water touches the hot glass of the baking dish, it causes an uneven increase in the thermal expansion. If the contraction and expansion is significant enough it will break.

Identifying Stress Cracks?

Thermal stress cracks in windows are easy to identify because they start perpendicular to the glass edge and will extend about a half-inch straight away from the glass edge. Just be aware that cladding and trim can hide the edge of the glass, so you may not see them right away. After the first half-inch of the crack, it may spider in any direction.

Sunrise Windows technicians recognize three general types of glass cracks:

Thermal Stress Crack-cracks at a perpendicular angle. Mostly caused by sudden temperature swings or shading changes on a house, typically cracked in the interior.

Impact Crack-cracks in a starburst pattern radiates from a central point. Hitting a window with a baseball or golf ball could result in an impact crack.

Pressure Crack-cracks in a pattern similar to the curve of a hourglass. Insulating glass windows with two panes of glass that have air inside them-may get pressure cracks if they are installed at too high or too low of an elevation level or if there are drastic pressure system changes in the weather.

Common Causes for Stress Cracks

Now that you know what causes cracks, you need to examine the window. Large windows are more prone to cracking than smaller ones, particularly if they're beneath overhangs or are recessed behind a protruding wall. This is because shadows from these overhangs create an extreme change in glass temperature-the shady side is cool and the sunny side gets hot and once the expansion and contraction of the glass becomes too much, it cracks,

Seasonal factors, like dramatic overnight temperature changes, hot temperatures during the day and then much cooler temperatures at night are the most common stress cracks as well.

Can I Prevent Stress Cracks?

The short answer is not really. Stress cracks are naturally occurring result of expanding and contracting glass due to temperature changes. However, in existing homes, installing thicker, stronger replacement panes of glass and choosing glass features such as heat-strengthened, tempered or tinted glass to help resist cracking.

If your planning a new addition or new construction project, preventing stress cracks in new windows starts at the architect stage. Work with your architect and control the amount of risk for glass cracking by choosing different glass options.

How Do I Fix a Glass Crack?

If you have a Sunrise Windows product in your home and discover a glass crack, go to Sunrise Windows web site under "Service Request" and fill out your information, a Service Technician will assist you in your replacement of the glass needed for your window from our pre-customer pricing plan. See Sunrise Windows Product Warranty on Glass Breakage.


1.Pella Windows

2.Jeld-Wen Windows

3.Weather Shield Windows & Doors

4.Canadian Insulated Glass Ltd.

Typical Stress Crack

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