What do terms such as "6 chambers", "Class A" and "wall thickness", which often appear in PVC window quotes, actually mean? We explain these technical terms in plain language, along with the TS EN 12608 standard, profile depth and steel reinforcement.
When you get a quote for PVC windows, you come across technical terms such as "5-chamber profile", "Class A" and "70 mm system". These terms describe how well the window will insulate, how sturdy it will be and how it will behave over the years. However, they are often used without explanation, which makes comparison difficult. In this article we explain what the number of profile chambers and wall thickness mean, why they matter and how to interpret them when evaluating a quote.
What Is a PVC Profile?
The frame and sash of a PVC window consist of hollow profiles produced by extrusion. When these profiles are cut, you can see many cavities separated from each other by thin walls. The walls forming the outer surface of the profile are called "outer walls", and the partitions inside are called "inner walls". Both the arrangement of these cavities and the thickness of the walls directly determine the window’s performance.
What Does the Number of Chambers Tell You?
A chamber is each enclosed air cavity in the profile cross-section. Because still air is a good insulator, chambers separated from one another inside the profile make it harder for heat to pass from one side to the other. Heat encounters an obstacle at every chamber wall.
While 3-chamber profiles were common in the past, today 5- and 6-chamber systems are generally preferred for homes, and 7-chamber profiles are also used in projects aiming for higher energy performance. However, the number of chambers alone can be misleading. Dividing a profile of the same depth into a larger number of very small chambers does not always increase insulation proportionally. For this reason, the number of chambers must always be considered together with profile depth.
Profile Depth
Profile depth is the dimension of the window in the direction of the wall thickness, expressed in values such as 60, 70, 76 or 82 mm. Deeper profiles make room for more chambers and also allow thicker glazing units to be used. For example, if triple glazing is wanted, the glazing rebate must be deep enough to hold that thickness.
Wall Thickness and TS EN 12608 Classes
Wall thickness is the thickness of the profile walls in millimetres. The window’s mechanical strength, the soundness of its welded corners and the holding power of its screws depend largely on the thickness of the outer walls. The TS EN 12608 standard classifies PVC window profiles according to their outer wall thickness:
| Class | Visible outer wall | Non-visible outer wall | Assessment |
|---|---|---|---|
| Class A | ≥ 2.8 mm | ≥ 2.5 mm | Recommended for homes, the sturdiest class |
| Class B | ≥ 2.5 mm | ≥ 2.0 mm | Thinner-walled, economical option |
| Class C | No specific limit | No specific limit | Not recommended where a long life is expected |
In Class A profiles, welded corners are more durable and hinge and lock screws hold more firmly. This difference is not visible on the first day, but it shows ten years later in whether the sash sags or cracks appear at the corners.
The Role of Steel Reinforcement
PVC on its own is not rigid enough to span large openings. That is why galvanised steel reinforcement is placed in the main chamber of the profile. The reinforcement provides resistance to wind load, prevents the sash from sagging and allows hardware screws to grip metal. The thickness and cross-section of the reinforcement should be chosen according to window size and colour. Reinforcement becomes even more important in dark-coloured profiles, which heat up more in the sun.
How to Interpret a Quote
- Do not look only at the number of chambers: Consider it together with profile depth and class.
- Ask for the class in writing: Instead of general phrases such as "thick profile", look for Class A or B information in the quote.
- Ask about reinforcement: Whether there is reinforcement and how thick it is matters greatly, especially for large openings.
- Look at overall performance: The profile is only part of the window area; the glazing unit and installation are at least as important as the profile.
What Do We Recommend for Our Region?
Around Ortaca, Dalaman and Köyceğiz, summers are hot and solar radiation is high, while wind and salty air are significant along the coast. In these conditions, Class A profiles at least 70 mm deep, with 5 or 6 chambers and suitable steel reinforcement, are a balanced choice in terms of both thermal insulation and long life. For wide terrace doors and sliding systems, reinforcement and profile strength become an even higher priority.
In holiday homes, windows may stay closed for long periods and profile surfaces can reach high temperatures in the summer sun. In this kind of use, thick-walled, well-reinforced profiles offer an additional advantage in keeping the sashes in shape and the gaskets seated properly. Holding a profile cross-section in your hand during the survey is the easiest way to understand the difference between the classes.
Conclusion
The number of chambers tells you about thermal insulation, and wall thickness tells you about strength and lifespan. Both make sense when read together with profile depth and steel reinforcement. Ask for this information clearly when comparing quotes. During a free site survey our team shows you profile cross-sections on site and explains the differences in concrete terms.
