When it comes to energy-efficient building envelopes, windows are often the weakest link. Inefficient windows can account for a substantial share of a building's heating and cooling losses, driving up utility bills and reducing occupant comfort. The AW90 Passive Window from ALPES redefines what aluminum-framed fenestration can achieve, delivering a thermal K-value as low as 1.3 W/m²K through thoughtful engineering and premium materials.
In this article, we break down the thermal performance of the AW90 passive window system — how it works, what makes it different from standard aluminum windows, and why it matters for your next project.
The K-value (also referred to as U-value in some regions) measures the rate of heat transfer through a window assembly. The lower the number, the better the insulation. A K-value of 1.3 means the window allows only 1.3 watts of heat to pass through each square meter of surface for every degree of temperature difference between inside and outside.
To put this in perspective, a standard single-pane aluminum window might have a K-value of 5.0 or higher. Even many modern double-glazed aluminum windows fall in the 2.5–3.5 range. At 1.3, the AW90 cuts heat loss by roughly half compared to a typical double-glazed aluminum window — a difference that shows up clearly on energy bills, especially in cold climates.
Aluminum is an excellent structural material — strong, lightweight, corrosion-resistant, and dimensionally stable. But it is also a natural conductor of heat, roughly 500 times more conductive than fiberglass. The challenge for any high-performance aluminum window is breaking that thermal bridge. The AW90 solves this problem through a layered approach to insulation.
At the core of the AW90's thermal strategy is a multi-chamber insulation strip combined with insulation sponge. Unlike a simple single-cavity thermal break, the multi-chamber design creates several dead-air pockets within the frame. Each chamber slows down heat transfer a little more, stacking up to a significant overall reduction in thermal conductivity. The PA66GF25 polyamide material used for the insulation strip has a thermal conductivity of roughly 0.3 W/m·K — far lower than the aluminum it separates.
Even the best insulated frame leaks energy if air can move through the gaps. The AW90 employs a dual-matrix eight-layer sealing system that includes extended seals, composite seals, welded corner seals, threaded seals, and dense sealing strips. Every point where the sash meets the frame — top, bottom, left, and right — is sealed multiple times over. The result is not only superior thermal performance but also exceptional sound insulation and weather resistance.
Where many windows rely on mechanical fasteners and gaskets alone, the AW90 uses a full injection adhesive process across the frame, mullion, glass sash, and screen. This creates a monolithic, seamless bond that eliminates micro-gaps through which heat and air could otherwise pass. The corner joints, a common weak point in window assemblies, are fully sealed with injection-molded structural adhesive for a continuous thermal barrier.
The AW90 uses 6060-T66 grade aluminum profiles with a wall thickness of 1.8mm, meeting the new national standard for structural performance. The T66 temper provides enhanced strength and dimensional precision, ensuring the frame stays perfectly straight and true over decades of use. This precision matters for thermal performance because even minor frame deformation can compromise seal integrity. The closed-chamber pressline structure, used for both opening and fixed panels, adds further structural rigidity and improves the overall thermal envelope.
The 1.3 K-value is not the result of any single feature. It is the product of a system in which every component is engineered to work together toward the same goal: minimizing heat transfer. The multi-chamber thermal break handles conduction through the frame. The eight-layer sealing system stops convection and air leakage. The high-precision profiles ensure that all seals remain perfectly aligned under real-world conditions. And the insulated glass unit (available in multiple configurations) handles the largest surface area of the window.
It is this systems-level approach that sets the AW90 apart from budget aluminum windows that may advertise low U-values but only achieve them in idealized lab conditions with specific glass configurations. The AW90 is designed to deliver consistent thermal performance in actual installations, across its full range of sizes and glass options.
Lower energy bills are the most obvious benefit of a high-K-value window, but the AW90 delivers several additional advantages that building professionals and homeowners value:
The AW90 is an inward-opening tilt and turn windows system, offering two modes of operation in a single unit. In tilt mode, the window opens inward from the top for secure ventilation — ideal for rainy days or when you want fresh air without leaving the window fully accessible. In turn mode, the entire sash swings inward like a door, making it easy to clean both sides of the glass from inside the building.
This European-style design is particularly well-suited to high-rise buildings, safety-conscious homes, and any application where easy cleaning matters. The 360-degree locking points provide full-perimeter security, with 5,000N shear resistance strength at the corners. Hardware is supplied by Winkhaus — a German manufacturer with 169 years of engineering heritage — with optional ROTO C-slot hardware available for projects that prefer that specification.
The AW90 Passive Window is designed for projects where energy efficiency, durability, and design quality matter. It works equally well in luxury residential villas, mid-rise apartments, and light commercial buildings. The slim frame profile and flush design give it a clean, modern aesthetic that complements contemporary architecture, while the robust construction ensures it will perform reliably for decades.
As a leading casement window manufacturer based in China, ALPES produces the AW90 in its 100,000 m² manufacturing facilities in Foshan and Zhaoqing, Guangdong. The company exports to countries worldwide and manufactures according to international building codes. Custom color matching, glass configurations, and hardware options are available to meet specific project requirements.
If you are planning a project that demands high thermal performance without sacrificing the strength, durability, and design flexibility of aluminum, the AW90 Passive Window is worth a closer look. Its K-value of 1.3, eight-layer sealing, and precision German hardware combine to deliver a window that performs as good as it looks.
