Window tips

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3 minutes of read

Cracks in the glass of PVC windows – how do spontaneous cracks in the glass occur?

Glass cracks in PVC windows can occur for various reasons. If they are hit by a sharp object, slam the window or shatter. But what if spontaneous glass breakage occurs, and is it even possible? It turns out that it is.

Spontaneous breaking of glass and on temperature resistance

The temperature resistance of glass is limited, which is why glass exposed to unfavorable temperature differences can break on its own – or even spontaneously – under certain circumstances, without anyone being able to do anything about it. Significant temperature differences in insulating glass panes lead to internal stresses, which in turn can directly cause the panes in a window to break. These stresses usually result from solar radiation – the temperature inside the chambers can reach up to 90 degrees Celsius!

High stresses in glass usually occur when the glass is heated unevenly on its surface. If one edge of untempered float glass is cooler than the other and this difference exceeds 30 degrees Celsius, a critical value is considered to have been reached. The result? Cracked glass. This situation is caused not only by the heat of the sun but also by a radiator or a lamp near the windows.

Cracked glass from the inside – what should you look out for

Curtains that come into contact with the glass can also cause spontaneous cracks in the untempered glass. Remember to leave a gap of at least 25 mm between the glass and the curtain, as air circulation must be ensured here to prevent the glass from breaking. Few people know that the unfavorable positioning of furniture, such as armchairs, can also have an impact on the phenomenon of spontaneous glass breakage.
When glass panes break thermally, the characteristic patterns shown in the following figure appear on the glass pane. Typically, the crack begins at a right angle, from the edge into the glass surface, but the crack may change direction several times.

Even if only one insulating glass pane in your PVC window is cracked, it must be replaced. The space between the panes is filled with an inert gas. If it escapes, the window will no longer insulate and water vapor will soon appear in the spaces between the panes. Repairs should be carried out only by a qualified professional. To do this, go to the point of sale where you bought your windows. A consultant will check the nature of the damage and have the glazing package replaced – without having to replace the whole window.

Cracked window glass – 5 rules to avoid thermal cracks

Cracks in glazing caused by thermal stress are not a defect in the glass and are not covered by warranty, so it makes sense to educate yourself on how you should care for your glazing to minimize the risk of this happening. As you already know, the main cause of glass breakage is the low temperature resistance of the glass – for example, the glass of a window will break if there is a sudden change in temperature. Here are the top 5 rules to follow when using your windows.

  • do not place furniture near the window panes,
  • do not put foils or posters on the windows,
  • do not direct cold air from the air conditioner or hot air from a heater directly at the window,
  • leave a gap between the curtains and the window pane to allow optimal air circulation,
  • if you want to buy shutters, choose those with perforations and not ones that are completely impermeable to the sun;

If you are about to buy new windows and know that they will be put to the test in terms of temperature fluctuations, opt for our installation of tempered glass. It is characterized by high resistance and is five times stronger than ordinary float glass. The tempering process causes a favorable change in the internal stresses in the glass structure, making it more resistant. When you choose this type of glazing, you invest in peace of mind and safety.