There’s a common stereotype that aluminum windows are cold, while PVC windows are significantly warmer. In reality, this is a misconception. Yes, aluminum is a material with high thermal conductivity. But there are a number of technologies that help retain heat inside the room, effectively making aluminum windows warm. In this article, I’ll break down what you should pay attention to in order to ensure your aluminum window is energy-efficient and warm.
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Thermal break
There’s another common stereotype borrowed from the PVC window market: the deeper the installation depth, the warmer the window. But for aluminum windows, the main indicator of energy efficiency is the characteristics of the thermal break.
Thermal break is an insulating polyamide barrier placed inside the window or door frame. It acts as a divider, separating the profile into two zones: the interior, which stays warm, and the exterior.
The width of the thermal break directly affects heat transfer. The smallest thermal break is 24 mm. It’s used in systems like SIAL KTP74 and Alutech W62. These systems have identical thermal performance, even though their installation depths differ.
Here, the principle truly applies: the wider, the better! There are systems on the market with a 40 mm thermal break. For example, the MASTERLINE 8 series from the leading European manufacturer Reynaers. It comes in three variations: STANDARD, HI, and HI+, which differ in the presence of foam inserts. We’ll talk more about those a bit later.
An even wider thermal break — 60 mm — can be found in the MASTERLINE 10 series from the same manufacturer.
Foamed thermal materials and gaskets
Another very important point is the foamed inserts in the thermal break. The more inserts there are, the warmer your window becomes! They stop convection — the transfer of heat through air.
Seals also play an important role. They create an impermeable barrier against external elements such as dust, wind, and moisture. Seals significantly affect the overall thermal insulation performance, ensuring indoor comfort without heat loss.
They can be made from different materials:
- Rubber (an inexpensive option, not resistant to frost),
- Thermoelastoplast (an inexpensive option, not heat-resistant — softens when heated),
- EPDM (an optimal modern material with high thermal resistance),
- Silicone (an expensive option with enhanced performance and durability).
The number of sealing contours also matters. The central seal is installed continuously around the perimeter of the window. External seals may be interrupted due to hardware, but we will come back to that later. On my projects, I prefer to use EPDM inserts.
Choosing a warm glazing unit
Heat retention is affected by a special coating applied to the glass. This is a technology of depositing metal particles on the surface of the glass, which gives your windows various useful properties. One of them is energy efficiency. This type of coating significantly reduces heat loss by keeping warmth inside the room and preventing it from escaping outside.
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Glass coating
Heat retention is also influenced by special coatings on the glass. This technology deposits metal particles on the surface, reflecting heat back into the room and preventing it from escaping outside.
Spacer frame
The choice of spacer bar can also affect heat retention. This spacer is placed between the glass panes around the perimeter. By default, it is usually made of cold aluminum. However, you can choose a plastic one, which is considered warm. Using a plastic spacer helps prevent condensation from forming along the perimeter due to temperature differences.
Inert gas
You can enhance the thermal insulation properties of an insulating glass unit by using inert gas instead of air between the glass panes. Typically, this is argon (Ar) or krypton (Kr). These gases help improve the thermal insulation performance of the IGU. Thanks to this type of filling, warm air escapes from the room more slowly.
Which gas to choose? Krypton (Kr) improves thermal insulation performance by 2 times compared to standard options. Argon (Ar) is slightly less effective, improving performance by 1.2–1.5 times. Additionally, sound waves travel slower through krypton than through argon. As you can see, inert gases significantly enhance the characteristics of the insulating glass unit. Which one to choose—it’s up to you.
There is a myth that inert gases can be toxic. In reality, gas leakage from a hermetically sealed chamber happens extremely slowly—on a molecular level.
Important! Even if the glass unit breaks or cracks due to a manufacturing defect or poor installation, your health is not at risk, because the gas is safe.
For more details on the key characteristics of insulating glass units, read the article: How to choose the right IGU for your home?
Hardware
As promised, let’s return to the topic of hardware. I always recommend my clients to use concealed hinges. Some manufacturers, like Schüco, have completely moved away from traditional surface-mounted hinges.
Concealed hinges look much more aesthetically pleasing. But more importantly, their use improves window airtightness. When installing standard hinges, the sealing gasket between the frame and sash must be cut. Over time, this can lead to drafts at those points. With concealed hinges, the sealing contour remains intact.
Conclusions
I hope I was able to dispel the myth that aluminum windows are cold. If that were really the case, aluminum glazing wouldn’t remain such a strong and ongoing trend. Aluminum glass structures are highly durable — their service life exceeds 80 years! Thanks to their ability to bear heavy loads, there are virtually no limits when it comes to architectural ideas. Modern technologies make aluminum windows truly energy efficient! Because of this combination of features, you can now build homes with maximum panoramic glazing. Aluminum structures are literally replacing walls — and the home will still stay warm!
