Class A profiles for large-format glazing: a guarantee of long window lifespan

The quality of the window frame profile plays a key role in the issue of strength and shape stability of the window. Not every frame can withstand a load of up to 160 kilograms in the long term, which could be the weight of a square window with an edge of four meters, for example. Therefore, attention should be paid, especially to large-format glazing, to the wall thickness of the main profiles, where every millimeter can matter.

The choice of windows is one of the most important points during the construction or renovation of a property, not only in terms of the amount of light they let into the interior. Their size and the material used also have a fundamental impact on the thermal balance and climate in the home. If the plans include large-format windows, it is better to turn directly to their manufacturer, as the quality requirements are far higher in this case – especially concerning the load-bearing capacity of the window and its static properties.

Wall Thickness of the Main Profiles

Especially with large glazed areas, it is important to choose a frame that will have a long lifespan, safely carry heavy insulating glass, endure frequent handling, and not deform. The wall thickness of the main profiles has a decisive influence on these requirements. Given the energy standards, which essentially consider insulating triple glazing as standard, using only Class A profiles in their production is the safest option for the long lifespan of windows. The wall thickness of the main profile in this category is at least 2.8 millimeters, while in Class B, it is 2.5 millimeters.

“The trend of large and heavy glazed areas logically brings a significant increase in the load on frame constructions. By using Class A profiles for the operable parts of the windows, you essentially eliminate problems such as wing deformation, profile deflections, leaks, or hardware pull-out, which threaten less stable profiles. A difference of at least 0.3 millimeters in the wall thickness of Class A main profiles compared to Class B may seem negligible, but it has a significant impact on the long-term load-bearing capacity, stability, and strength of the window,” says Milan Klepsa, the chief representative of VEKA, a leading global manufacturer of Class A plastic window and door profiles. It is therefore important to realize that with a four-millimeter thickness of glass, triple glazing will be a third heavier than double glazing. For large formats, however, it is necessary to use thicker glass (from six millimeters). A double-glazed window with an area of four square meters will weigh approximately 80 kilograms, while a similarly sized triple-glazed window will have double that weight.

Testing Center

With the increasing size of the area, the use of Class A plastic window profiles – defined by standard ČSN EN 12608 – is not only reasonable but actually necessary. However, the stability and load-bearing capacity of the profiles are not only conditioned by standards but also by a series of demanding tests at the manufacturer. “Windows and doors made from our profiles undergo rigorous testing in the certification and testing center in Sendenhorst, Germany. They must withstand impacts from a pendulum weight of 50 kilograms or vertical pressure in the corner of the frame ranging from 200 to 800 newtons. When we convert this to weight units, it represents a load of about 20 to 80 kilograms, which the products must endure without damage,” adds Milan Klepsa.