A wind test for a casement window is not a single number on a brochure. It is a controlled laboratory procedure that answers one practical question: how much wind pressure can this exact window take before it bends too far, leaks, or breaks? For buyers specifying windows on a villa near the coast or a tower in a windy city, that answer decides whether the glass stays in the frame during a storm. This article walks through what the China casement window wind test measures, the standard behind it, and how to read the result against the construction of real aluminium casement systems.
A window is mounted in a sealed pressure chamber with its outer face exposed to a controllable air pressure. The lab then applies positive pressure (wind pushing the sash inward) and negative pressure (suction on the leeward face pulling the sash outward), often alternating, and watches what happens. Three things are recorded: the frontal deflection of the main load-bearing members (the sash stile and the frame), the residual deformation after the pressure is released, and any sign of failure - a hinge that lets go, a corner that cracks, glass that breaks, or a sash that will no longer close and lock. In China this is one of the three mandatory performance tests for exterior windows and doors, run alongside airtightness and watertightness on the same specimen.
The current reference is GB/T 7106-2019, the standard for air permeability, watertightness and resistance to wind load of exterior windows and doors. It folded the older separate standards into one document and describes a three-phase sequence:
The final grade is the lowest grade recorded across the three test specimens. Wind-load resistance is split into nine grades: grade 1 starts at a P3 of 500 Pa and grade 9 reaches 4500 Pa and above. As a practical rule, projects in coastal or typhoon-exposed zones are specified at grade 6 or higher (P3 at least 3500 Pa), while sheltered inland sites may be acceptable at grade 1 to 2. Other markets use equivalent methods - the European family of standards such as EN 12211 applies the same three-pressure logic with its own classification bands.
Understanding the test helps you read a spec sheet. Wind pressure lands on the glazed sash. From there the force travels through the hinges into the outer frame, through the corner joints into the fixed frame, and finally into the wall through the anchors. Two parts decide whether the window passes:
The glass is not a passenger either. A properly glazed insulating unit acts as a diaphragm and is itself measured for center deflection. A bigger, thinner pane moves more.
ALPES builds its casement range on the same structural backbone - 6060-T66 aluminium at 1.8 to 2.0 mm wall thickness with PA66GF25 multi-chamber thermal breaks - and differentiates the models by frame depth, glass-sash depth, corner process and hardware. The table below is a construction map; it shows what each system is made of, not a wind-pressure rating. The rated class for your project must come from a test certificate that matches your exact opening size and glass build.
| Model | Profile (grade / wall) | Frame width | Hardware | Wind-relevant construction |
|---|---|---|---|---|
| C120 (outward) | 6060-T66 / 1.8-2.0 mm | 119 mm | ROTO transmission box + anti-pry lock points | Full standard square cavity for superior wind-pressure and deformation resistance |
| C113 (outward) | 6060-T66 / 1.8-2.0 mm | 113 mm | CMECH (Red Dot, 30,000 cycles) | 8 mm-thick profile + full glue-injection corner brackets for monolithic rigidity; triple sealing |
| C116 (outward) | 6060-T66 / 1.8-2.0 mm | 116 mm | German Wehag (upgrade) | 304 stainless high-load hinges; 34-44 mm multi-chamber insulation; welded corners |
| AW90 (tilt-turn) | 6060-T66 / 1.8 mm | 90 mm | Winkhaus (169 yr) or C-Slot ROTO | 360 degree locking points; 5,000 N shear resistance; full injection-adhesive corners; 240 h salt spray |
These are product construction values taken from the ALPES catalogue. They explain why the systems resist wind well, but they are not a substitute for a graded test report. Ask ALPES for the certificate that lists the P1/P2/P3 and the deflection measured on a specimen built to your dimensions.
Because casement window sizes set the span of every member, they are the single biggest lever on the result. A 600 mm-wide casement and a 1200 mm-wide casement made from the same profile will not earn the same grade - the wider sash bends more at the same pressure. Other factors:
When a supplier hands you a certificate, check four things:
None of this matters if the window that ships is not the one that was tested. When you buy through a wholesale casement windows channel, tie the certificate to the production batch and keep the spec locked. A custom casement window with a wider sash, a 90 degree handle option or a different glass unit changes the load path, so the test evidence must match the exact build you receive - not a look-alike model number. Work with a manufacturer that can show the construction behind the grade and supply the graded report per your project dimensions, and the wind test becomes a number you can actually build around.
ALPES manufactures its casement range in a 100,000 m2 facility in Foshan and Zhaoqing, Guangdong, and supplies villa and commercial projects across Saudi Arabia, Dubai, the wider Middle East and Australia. If you are specifying casement windows for a wind-exposed site, send your opening schedule and glass specification and ask for the wind-pressure class certificate that matches it.
