ADS 90 SI sits at the top of the entrance-door range, combining certified security with a thermal figure that competes with modern window systems. The „SI” suffix stands for super insulated — not a marketing phrase but a distinct construction with an enlarged, chambered thermal break.
Certified security
Depending on the hardware set the door can be built to RC2 or RC3. That level of protection is particularly relevant on detached houses on the edge of towns, where the front door is often the single most exposed opening on the property.
Thermal figures in the same league as windows
Uw values from 0.87 W/m²K are unusual for entrance doors, where mass and threshold detail typically make low U-values hard to achieve.
Where it makes sense
ADS 90 SI earns its place on higher-specification new builds and on deeper Hertford refurbishments where the goal is both to raise security and to close a persistent thermal weak spot in the elevation.
For readers researching options locally, 5EC's front doors and 5EC's premium line are both worth reviewing — both are handled by 5EC, a Stevenage-based authorised supplier working across Hertfordshire.
Detailed technical documentation is available on Schüco's product page.