77IW Open-In Window


High performance Open-In Window

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 and is our highest performing window yet.

Insulated centre seals, high performance thermal break materials and extra insulating foams mean this is a window which can achieve impressively low U-Values even with standard double glazing.

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



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.


Modern contemporary styles and a wide variety configurations delivering high levels of thermal performance through 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.

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