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APLAST

PVC Windows Guide: Number of Chambers, Construction Depth and the Difference Between Class A, B and C PVC Profiles

mostra profil pvc color ferestre termopan aplast

PVC Windows Guide: Number of Chambers, Construction Depth and the Difference Between Class A, B and C PVC Profiles

If you have ever requested a quote for windows, you have certainly come across terms such as “6-chamber profile”, “70 mm profile”, “Class A” or “3 seals”. These are real and relevant specifications, but when presented separately, they can give you an incomplete picture of a window’s overall performance.

A PVC window is not high-performing simply because it has more chambers or a deeper profile. The final performance is the result of several components working together: the PVC profile, its geometry, the number and positioning of the chambers, the construction depth, the sealing gaskets and, perhaps surprisingly, its colour.

In this article, we will explain why each specification of a PVC profile matters, so that when comparing two windows, you can look at the system as a whole rather than focusing on a single figure in the quotation.

What does “number of chambers” mean in a PVC profile?

The internal chambers of a profile act as small barriers of still air, reducing heat and sound transfer. The more chambers there are, and the greater the construction depth of the profile, the longer and more fragmented the path that heat or sound has to travel from the outside to the inside.

Although a PVC profile with multiple insulating chambers is desirable, to achieve maximum efficiency the chambers need to be proportionally dimensioned to the installation depth. Therefore, a 76 mm profile with 6 chambers can achieve better thermal and acoustic performance than a 60 mm profile with the same number of chambers, because the former has wider and more efficient compartments.

General guideline:

  • approx. 60 mm / 4 chambers – solutions intended for construction and renovation projects with standard requirements and an optimised budget;
  • approx. 70 mm / 5–6 chambers – solutions suitable for a wide range of residential applications;
  • approx. 76 mm / 5–6 chambers – systems offering higher thermal performance and greater flexibility for advanced glazing units;
  • approx. 82 mm / 7 chambers – systems designed for very high levels of energy efficiency, depending on the selected configuration.

PVC profile class (EN 12608)

The European standard EN 12608 classifies PVC-U profiles according to the wall thickness of their main profile sections. The current classification distinguishes Classes A, B and C based on the thickness of the visible and non-visible walls.

For main profiles:

  • Class A: ≥2.8 mm on visible surfaces and ≥2.5 mm on non-visible surfaces;
  • Class B: ≥2.5 mm on visible surfaces and ≥2.0 mm on non-visible surfaces;
  • Class C: no minimum wall-thickness requirement for these classification criteria.

The difference in wall thickness may seem small, but profile design and wall thickness can contribute to structural rigidity and the way components are secured.

Structural rigidity

A Class A profile has thicker main walls, which can provide increased resistance to repeated opening and closing, the weight of the glazing unit and wind loads, depending on the complete window configuration.

Better component fixing

The thicker walls of a Class A profile can provide better anchoring for fixing screws and contribute to the long-term stability of the window and its hardware.

Sealing gaskets

Sealing gaskets are synthetic rubber elements, commonly made from materials such as EPDM, that ensure a tight contact between the moving sash and the frame.

A high-performance profile can use three perimeter sealing gaskets: one on the inner side, one in the central sealing plane and one on the outer side. This three-level configuration creates successive barriers against air, water and noise.

  • 3 seals: enhanced air, water and acoustic sealing;
  • 2 seals: standard sealing performance.

Sealing gaskets require periodic maintenance. Annual treatment with dedicated silicone-based products helps maintain their elasticity and extend their service life. A neglected gasket can become the weak link in an otherwise high-performing window system.

PVC profile colour and thermal effects

The range of colours and finishes available for PVC profiles has expanded considerably in recent years. Beyond classic white, you can choose from anthracite grey, matt black, brown or wood-effect finishes.

White PVC reflects most solar radiation and can heat up to approximately 40–50°C on hot days. A dark-coloured profile, such as anthracite grey or black, can absorb significantly more solar radiation on a south-facing façade and reach temperatures of 70–80°C. At these temperatures, thermal expansion of the profile becomes significant.

The consequences of an installation that does not account for this phenomenon appear gradually: the profile may deform slightly, the sash may no longer close perfectly and airtightness can progressively decrease. These problems can be avoided when installation is carried out correctly from the beginning, with the necessary expansion tolerances and strategically positioned fixing points.

There is also a second complementary measure, independent of installation: external solar shading systems. External roller shutters, blinds or awnings reduce the temperature reached by the profile on days with intense solar radiation — increasingly common in Europe in recent years — protecting both the profile and the interior of the home from overheating.

A strategic advantage of deeper PVC profiles: future flexibility

A less frequently discussed argument for choosing a profile with greater construction depth, such as 76 mm or 82 mm, is the flexibility it can provide in the future.

Deeper profiles can accommodate a wider range of glazing units, from conventional double glazing to specialised triple-glazed units exceeding 50 mm in total thickness. This means that if you choose a standard glazing configuration today for budget reasons, the profile may be able to accommodate a higher-performance glazing unit later if your needs or financial possibilities change — without replacing the entire window, but only the glazing unit.

How do you choose the right PVC profile?

There is no single profile that is suitable for every project.

Your choice should take into account the type of building, window dimensions, façade orientation, desired comfort level, glazing unit and budget.

For renovations and projects with an optimised budget

A system of approximately 60 mm / 4 chambers can be a suitable solution when energy-efficiency requirements are moderate and the window configuration is standard.

For modern residential homes

Systems of approximately 70 mm / 5–6 chambers offer a good balance between energy efficiency, flexibility and cost and can accommodate high-performance glazing configurations.

For energy-efficient homes

76 mm / 5–6 chamber profiles, combined with three seals, triple glazing and appropriate reinforcement, can be used to achieve high thermal performance.

For projects with very high performance requirements

For homes with specific energy-efficiency standards, including passive house projects, the entire window system and its performance in the actual configuration should be assessed.

Conclusion

Choosing a PVC window profile should not be based solely on the number of chambers or the construction depth. These are important criteria, but the actual performance of a window results from the way all system components work together.

When comparing two quotations, look beyond phrases such as “6 chambers” or “70 mm profile”. Check the construction depth, profile class, number and configuration of the seals. Do not overlook the colour of the profile either: dark colours installed on sun-exposed façades absorb more heat and can reach temperatures of 70–80°C, while thermal expansion can lead to deformation over time if the window is not installed correctly.

At the same time, a deeper profile can provide greater flexibility for using high-performance glazing units, while Class A profiles offer important advantages in terms of structural robustness and stability.

Need help choosing your windows?

At Aplast, every window is configured according to the profile, glazing unit, hardware and requirements of the project.

Tell us what you need, and we will help you identify the right configuration for your home.

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APLAST

Guide: How to Choose the Right PVC Windows for Your Home Based on Facade and Location

locuinta eficienta energetic ferestre termopan aplast

Guide: How to Choose the Right PVC Windows for Your Home Based on Facade and Location

Windows are one of the few decisions you make only once for a home. With a lifespan exceeding 30 years, making the right choice is essential for the long-term comfort and efficiency of your home.

A well-chosen and properly installed window directly contributes to reducing energy costs, eliminates the risk of condensation, dampens exterior noise, and offers a high level of security against break-in attempts. In contrast, a choice made solely on the basis of the lowest price can generate, over time, numerous inconveniences: frequent adjustments, thermal and acoustic discomfort, or insufficient performance for the actual environmental conditions in which the home is situated.

A window is a system. This is probably the most important thing to understand before opening the first catalogue or requesting the first quote.

A PVC window has four components that must work together: the profile (the PVC frame), the glass unit (double or triple glazing), the hardware (the opening and closing mechanisms), and the installation. Each of them contributes to the final performance.

Installation alone has an impact of up to 50% on the final insulation and performance properties of a window. A premium window installed carelessly becomes, within a few years, a mediocre window with condensation, draughts, and difficulty closing. Conversely, a flawless installation cannot recover the performance of a technically weak system.

The same principle applies within the window itself: the performance of a system is dictated by its weakest component. A 7-chamber profile paired with standard double glazing produces an unbalanced assembly — the profile cannot realise its potential, and the result is modest relative to the investment. A triple-glazed unit (which weighs approximately 50% more than standard double glazing — around 30 kg/m² versus 20 kg/m²) installed on a 3–4 chamber profile will put excessive strain on the hardware, causing the window to sag, fall out of alignment, and require frequent servicing.

Understanding this system logic is what separates a good purchase from one that looks good on paper but disappoints in practice.

Most people begin the purchasing process with the wrong question: “What windows are good?” The right question is different: “What windows are right for my specific situation?”

There is no universally optimal window. There are windows suited to a passive house facing north, windows suited to a ground-floor apartment in a city-centre block, and windows suited to a renovation with a defined budget in a 1970s building. The same products can be the perfect choice in one case and a waste of money in another.

Before opening the first catalogue or requesting the first quote, answer five questions about your building. The answers will filter and guide all the technical decisions that follow.

Facade orientation: How does the sun influence the choice of PVC windows

Modern glass can be configured with two partially opposing objectives: to maximise solar heat gain in winter (useful for north-facing façades or homes in cold regions), or to block a portion of solar radiation in summer (essential for south-facing façades). The parameter that governs this balance is called the solar factor (g-value), which we will detail in the chapter dedicated to glass. For now, remember the principle:

  • South-facing façade: the priority is solar control — glass with a low solar factor (g-value) ceduces indoor overheating in summer without significantly sacrificing natural light.
  • North-facing facade: the priority is maximum thermal insulation — the lowest possible Ug coefficient (glass that conducts as little heat as possible), without needing aggressive solar control.
  • East- and west-facing façades: a balance between the two.

Another effect of orientation concerns profile colour. Dark-coloured pcofiles (anthracite grey, brown, black) absorb far more solar radiation than white ones. A white profile reaches approximately 40–50°C on sweltering days. A dark-coloured profile on a south-facing façade can reach 70–80°C. At these temperatures, the thermal expansion of the PVC profile becomes considerable. If the installation is not carried out with the correct tolerances and strategically positioned fixing points, the result can be profile deformation, difficulty closing, or loss of sealing over time.

There is also a complementary measure, independent of installation: exterior shading systems. External roller blinds, venetian blinds, or awnings reduce the temperature the profile reaches on days of intense solar radiation, increasingly common across Europe in recent years, protecting both the profile and the interior of the home from overheating.

Climate Zone and Thermal Insulation (Uw)

The central parameter is the thermal transmittance coefficient Uw (U-window), which measures how much thermal energy the window loses per square metre for each degree of temperature difference between the interior and exterior. The lower the Uw value, the better the window insulates. The unit of measurement is W/m²K.

To understand in practical terms what different values mean:

  • Uw ~ 1.3–1.6 W/m²K — standard performance, suitable for renovations or commercial spaces with moderate requirements. Typically corresponds to 60mm profiles with 4 chambers and standard double glazing.
  • Uw ~ 1.0–1.3 W/m²K — good performance, suitable for standard residential buildings in areas with mild winters.
  • Uw ~ 0.8–1.0 W/m²K — high performance, recommended for new builds in areas with severe winters or for owners who prioritise energy efficiency.
  • Uw below 0.8 W/m²K — the territory of energy-efficient and passive houses. Windows in the Softline 82 series achieve Uw = 0.67 W/m²K, while the Deceuninck 76 goes as low as 0.62 W/m²K.

From a climate zone perspective, the practical rule is simple: the longer and more severe the winters in your area, the more quickly the investment in a lower-Uw PVC window pays for itself through reduced energy bills.

Type of construction: New house or apartment building

Determines what is technically possible:

  • New build: complete freedom — a high-performance profile is recommended. If you are building a new home, there is no technical justification for choosing an entry-level profile; the cost difference compared to a premium series pays for itself within a few years through energy savings.
  • Apartment in a block: constraints from existing openings, masonry, and installation; acoustic impact limited by the structure.
  • Old building / heritage property: there may be architectural or heritage restrictions limiting façade modifications, including profile colour or shape. Check before ordering.
  • Passive house: strict technical requirements, often specified in the design. Uw below 0.8 W/m²K becomes mandatory, triple glazing is the rule rather than the exception, and installation must completely eliminate thermal bridges. The chosen profile must be compatible with thick glass units — high-performance triple glazing can exceed 50mm in total thickness, requiring profiles with a construction depth of at least 76–82mm.

Floor, wind pressure and safety (RC Classes)

The position of the window within the building has two direct implications: wind pressure and break-in risk.

At higher floors, wind pressure on the window is significantly greater than at ground level. This means that the sealing and structural rigidity requirements for the profile are more demanding — a Class A profile with an outer wall of at least 3mm is not an optional upgrade, but a necessity for maintaining long-term performance.

At ground floor or first floor level, break-in risk is the main additional concern compared to a standard upper floor. The security of a window is provided by an integrated system — a rigid profile, multi-point hardware with certified break-in resistance (RC classes defined by the European standard EN 1627), and, optionally, laminated glass that does not shatter on impact but remains cohesive, blocking access.

Noise Level: When Acoustic Insulation Becomes a Priority

The acoustic performance of a window is measured in decibels of attenuation (Rw) and depends, similarly to thermal insulation, on the entire system — not just one element.

A few practical benchmarks:

  • Quiet residential area: standard double glazing provides sufficient attenuation (30–33 dB).
  • Urban street with moderate traffic: a window with a deep profile and acoustic double glazing (asymmetric panes of different thicknesses) can achieve 37–40 dB.
  • National road, busy boulevard: a dedicated configuration is required (6–7 chamber profile, triple glazing or acoustic double glazing with asymmetric panes). A well-chosen assembly can reduce exterior noise by 40–45 dB.

A relevant physical aspect: triple glazing offers approximately 20–30% more acoustic attenuation than standard double glazing, but maximum acoustic performance does not come automatically from the number of glass panes — it comes from the asymmetric configuration of thicknesses, which disrupts acoustic resonance.

Conclusion: There Is No "Best Window" — Only the Right Window for You

Choosing PVC joinery is a technical puzzle. As you have seen, an excellent profile can fail if the glass is not adapted to the façade, or if the installation ignores thermal expansion. The secret to a worthwhile 30-year investment is balance between these components.

Ready to make the right choice for your home?

Don’t leave the configuration of your windows to chance. A price quote without an analysis of your location is nothing more than a list of figures.

Our specialists will help you configure the perfect PVC window system, tailored to your climate zone and your family’s insulation needs.

Request a Free Quote
 
 
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