77IW Open-In Window


Why Choose Our AluK 77IW Windows?

The 77IW window is available in top, side or bottom hung configurations, all in a standard 77mm frame depth.

The modern slim lines and minimalist aesthetic make the 77IW an ideal choice for new build and contemporary refurbs. The slim frames mean there’s a larger glass area to let plenty of light flood in, and there’s even a choice of inward or outward opening frames for maximum flexibility.


The 77IW is very much a contemporary window system, but you can still match it to your own style with a range of colours, textures and customisation options – from glazing bars to leaded glass.

High Performance

The government’s Future Homes Standard, set to become law in 2025, sets some challenging new targets for the energy efficiency of windows and doors. Our impressive 77IW Open-In system already meets those targets with excellent insulated centre seals, high-performance thermal break materials and extra insulating foams.

Modern contemporary styles and a wide variety of configurations deliver high levels of thermal performance by incorporating technologies such as high-performance polyamides, insulated centre seals and profile foam insertions. The 77IW system also fully integrates with our curtain walling and door systems. They also provide Class 4 (600Pa) air tightness, Class E1050 (1200Pa) water tightness and Class C5 (2000Pa) wind load for the ultimate levels of performance for your home.

Technical performances

  Technical data
U value W/m²K 0.8-1.2 W/m²K
Air tightness (Pa) Class 4 (600 Pa)
Water tightness (Pa) Class E1050 (1200Pa)
Wind load (Pa) Class C5 (2000Pa)


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