Yes, a double-glazed window can shatter on its own, without any impact or external force. This phenomenon, known as spontaneous glass breakage, is usually caused by hidden manufacturing defects, severe temperature fluctuations, or excessive pressure building up within the glass unit.
Double glazing usually cracks due to thermal stress, poor installation, or impact damage. Because double-glazed units consist of two glass panes sealed tightly together, temperature fluctuations and structural pressures can cause the glass to expand, contract, or crack under tension.
When the temperature inside and outside the home contrasts too greatly, the window will be under increased pressure. The glass in your window will usually be strong enough to withstand this but extreme conditions or inherent weakness could cause the glass to crack spontaneously.
Sudden or Unexplained Cracks
While often called “spontaneous,” these are typically stress or edge cracks triggered by hidden imperfections, frame warping, or structural shifts. Common causes: Edge damage, thermal cycling, or manufacturing defects.
A double glazed window produced today will have a lifetime of 25-30 years and more if fitted in a sheltered location and not subject to any extreme weather. A double glazed window that does face exposed weather will expect a lifespan of 20 years.
Price Ranges Across Window Materials
Fitted uPVC window prices generally range between £450–£750 per window, depending on size, specification, and regional installation rates. Aluminium window prices begin around £600–£900 per window for supply only, with fitted costs typically between £800–£1,400 per window.
Signs that your double glazing has failed
Does home insurance cover broken windows? Homeowners insurance may cover damage to windows resulting from a covered peril listed on your policy. Your policy may also pay to repair or replace your neighbor's broken window if you or one of your family members are responsible for the damage.
Identifying stress cracks
Thermal stress cracks in windows are easy to identify because they start perpendicular to the glass edge. “It's easy to identify a stress crack if you can see the edge of your glass,” adds Howard. “The crack will extend about a half-inch straight away from the glass edge.”
Replacing only the glass is significantly cheaper than replacing the entire window. While you'll still need to pay for the glass and installation, of course, you won't need to buy a new frame.
The only real solution is to replace the damaged glass pane or the entire unit, if it's a double-glazed window. A temporary fix on a major crack is just buying time, and constant repair can cost more in the long run.
Many homeowners don't realize that while a uPVC frame can last for decades, the glass technology inside it has undergone a quiet revolution. If your double glazing was installed 20 or 25 years ago, you aren't just losing heat—you are essentially living with an “obsolete” level of insulation.
Yes, a double-glazed window can shatter on its own, without any impact or external force. This phenomenon, known as spontaneous glass breakage, is usually caused by hidden manufacturing defects, severe temperature fluctuations, or excessive pressure building up within the glass unit.
Although their appearance may be unsettling, most hairline cracks are normal and are often a result of: Natural building settlement (especially in newer homes) Thermal expansion and contraction. Drying shrinkage of plaster or concrete.
Often, window cracks are caused by sudden changes in temperate – or thermal shocks – which can occur when radiators are suddenly turned on, providing a sharp blast of heat on a cold day to unprepared double glazing units.
Thin cracks are usually not cause for concern, but you should consult a professional if they become wider than five millimetres. Diagonal cracks that look like staircase steps can be a sign of structural damage, and you should consult a structural engineer.
In this vein, your auto insurance can often step in to help you pay for the damage. It often will consider the crack an unpreventable accident, thus adding coverage. Even so, you might still face certain limitations in filing a claim for windshield damage. Let your insurance agent help you determine how they can help.
Avoid making guesses or unsupported statements about what caused the damage to your property. Speculating can lead to inaccuracies in the adjuster's report, potentially affecting your claim.
In many cases, it is cheaper to replace all windows at once. Full-home projects usually qualify for better per-window pricing because of manufacturing efficiencies, a single installation cycle, and lower labor per unit. You also avoid future price increases and start saving on energy bills sooner.
How to Get Homeowners Insurance to Pay for New Windows
Double glazing usually cracks due to thermal stress, poor installation, or impact damage. Because double-glazed units consist of two glass panes sealed tightly together, temperature fluctuations and structural pressures can cause the glass to expand, contract, or crack under tension.
Sleeping with windows open can introduce outdoor pollutants, allergens, and noise that disrupt rest. It also creates security vulnerabilities and allows pests inside. Furthermore, uncontrolled drafts can cause muscle stiffness and dry out your nasal passages.
Replace double glazing to benefit from the advancements in double glazing technology over the past 20 years. Today's windows have a U-value of 1.2 W/m²K compared to 2.8 W/m²K of older units. So they're more than twice as good at keeping heat in.