Slim Sash Casement Windows

Slim rebate sash casement windows from Warwick North West’s Innolux range blends an internally flush sash with an externally slim rebate for a sleek and clean look that is specifically designed to rival aluminium systems.

Available in a variety of configurations and styles, it brings better thermal performance than other PVCu and aluminium options at a similarly affordable cost for both trade and the end user.

Maximum performance wrapped in a smooth aesthetic

Delivering significant affordability over aluminium as well as enhanced thermal performance, slim sash casements reduce the cost of double glazing by anything up to 27%. The system’s innovative design means a lower glass specification can be utilised, readily compensated by one of the highest PVCu material options around.

As with all of our casement window styles, slim rebate variations achieve an ‘A’ WER rating and can deliver U-values as low as 0.7 W/m2K when triple glazed, far exceeding the Passivhaus standard. The six chambered design simply delivers high sought after energy efficiency with a co-ordinated, colour-matched aesthetic that offers installers a premium product that can be turned around quickly.

Slim rebate windows provide superb air tightness and thermal performance levels. They are guaranteed to reduce your home’s carbon footprint.

They provide excellent levels of durability and are extremely resistant to intrusion. With our energy efficient slim sash casements, Warwick North West are helping to support the drive for an affordable carbon free future.

  • Six chambered profile for increased thermal capability (U values 1.1 – 0.7)
  • Manufactured in a range of style sizes including fixed, top hung, bottom hung and side hung
  • Internally flush and externally slim rebate sashes that make for a sleek look
  • A range of grey and metallic finishes for those wanting to replicate aluminium
  • Customisable internal finishes for end user experimentation
  • A-Rated for sustainability, engineered from 50% post-consumer recycled PVCu


Innolux slim rebate windows are specifically designed to rival the clean aesthetics of aluminium systems, utilising high performance PVCu to better retain heat and be more affordable as a result. Providing end users with a sleek and contemporary profile that can be perfectly matched to any scheme or décor.


Aside from classic white, Innolux slim sash casement windows are available in the following colours: Black Ash, Anthracite Grey, Slate Grey, Moondust Grey, Anteak, Rosewood, Irish Oak, Cream and White Ash. Each former colour is effective at delivering a metallic aesthetic, being near-indistinguishable from genuine aluminium.


Warwick North West manufactures quality PVCu casement windows, which are designed to offer increased strength and security. Windows use ERA handles and Nico hinges, as well as ERA espagnolette and Nico shootbolt locking, protecting a property and giving the consumer complete peace of mind.


Innolux slim sash windows are manufactured using double glazed sealed units, with Planitherm Total Plus glass, Thermobar warm edge spacers, and Argon gas. This allows our casement windows to achieve an ‘A’ WER rating and U-values as low as 0.7 W/m2K, exceeding the Passivhaus standard.