AWS 90 SI+ is Schüco's top-of-range residential window and is specified where energy performance genuinely drives the design rather than being an afterthought.
Figures that used to be reserved for composite systems
A Uw from 0.62 W/m²K is a result that was, until a few years ago, largely the preserve of timber-aluminium composites. Achieving it in a pure aluminium window is technically noteworthy.
Sightlines and heritage-adjacent detailing
The narrow sightlines and available slimline options allow the system to sit convincingly on sensitive projects — a subject explored further in the heritage aluminium windows piece.
Not every project needs it
On a straightforward extension the additional cost of AWS 90 SI+ over AWS 75.SI is not always recovered in energy savings. The decision is best made once the wall build-up is fixed.
For readers researching options locally, 5EC's aluminium windows and 5EC's heritage aluminium range are both worth reviewing — both are handled by 5EC, a Stevenage-based authorised supplier working across Hertfordshire.
Detailed technical documentation is available on the AWS 90 SI+ specification.