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Cortizo Windows
Cortizo Cor 70 Hidden Sash — tilt-and-turn / casement aluminium window on a 70 mm thermally broken frame. The 'hidden sash' detail conceals the opening sash within the frame depth, so a closed window reads as a single fixed glass panel. BFRC A++ on top-spec triple-glazed builds, Class 4 air permeability (BS EN 12207, the maximum), PAS 24:2022 certified. Vitrum Solutions installs Cor 70 Hidden Sash across Buckinghamshire, Berkshire, Oxfordshire, Surrey and Hampshire.
Cor 70 Hidden Sash Specifications
System
Cor 70 Hidden Sash
Frame Depth
70 mm thermally broken
Energy
BFRC A++ on triple-glazed top spec
Air Permeability
Class 4 (BS EN 12207, the maximum)
Why Cor 70 Hidden Sash
Hidden Sash — concealed sash detail
The Cor 70 Hidden Sash hides the opening sash within the frame depth so a closed casement reads as a single fixed glass panel — there's no visible step where the sash meets the frame, just an unbroken glass plane and a slim outer frame. The architectural detail is most noticeable from outside, where the elevation reads cleaner than a standard casement window.
Tilt-and-turn / casement function
Two opening modes from a single handle position: tilt the top of the sash inwards for secure ventilation (the window is open but not hinge-clear so it can't be reached); full turn for cleaning the outside glass safely from inside (so the window is its own access point on upper floors). Used most often on first-and-above floor casements where escape access matters or where outward-projection is restricted by walkway / planting / boundary.
BFRC A++ on triple-glazed top spec
Cortizo's thermally broken Cor 70 Hidden Sash, paired with Class 4 air permeability (BS EN 12207, the maximum air-tightness rating) and triple-glazed Low-E units, achieves BFRC A++ — the top of the BFRC energy rating scale. Used on premium contemporary new builds and low-energy refurbishments where the window's thermal performance directly affects the building envelope's overall rating.
70 mm thermally broken frame
Polyamide thermal break separates the cold outside metal from the warm inside metal across the 70 mm frame depth. Multi-chamber profile keeps the structure dimensionally stable across UK seasonal temperature swings. Steel-reinforced frame internals on opening profiles for long-term frame straightness.
PAS 24:2022 + Class 4 air permeability
All Cor 70 Hidden Sash opening profiles are PAS 24:2022 certified with multi-point shootbolt locking, hidden hinges, internally-beaded glazing and laminated inner glass options. Tested to BS EN 12207 Class 4 air permeability — the maximum air-tightness rating, meaningfully reducing draughts and heat loss versus standard aluminium frames.
Aluminium Windows on Our Range
Cor 70 Hidden Sash feeds into our two aluminium window product pages depending on whether the architectural detail wanted is the standard casement frame or the slim flush-casement variant.
Get a free quote for Cortizo Cor 70 Hidden Sash Windows
Free no-obligation written quote. Fast response times. FENSA registered with a 10-year CPA insurance-backed guarantee. Serving Buckinghamshire, Berkshire, Oxfordshire, Surrey, Hampshire, Hertfordshire & West London.
Other Cortizo Systems
Bifolds, sliders, lift-and-slide and aluminium front doors are covered by purpose-built Cortizo profile systems — all supplied and fitted by Vitrum Solutions.
Cortizo Bifold
Bi-Fold and Bi-fold Plus Door (slim premium 110 mm reduced central junction).
View Bifold →Cortizo Sliding
Cor Vision Sliding (34mm interlock) and Cor Vision Plus Sliding (20mm central junction).
View Sliding →Cortizo Lift-and-Slide
4700 Sliding Patio and 4900 Sliding HI for medium-large lift-and-slide openings.
View Lift-and-Slide →Cortizo Millennium Plus
70 / 80 mm aluminium entrance door range with PAS 24 multi-point locking.
View Millennium Plus →Cortizo Windows — Frequently Asked Questions
What is Cortizo Cor 70 Hidden Sash?
Cor 70 Hidden Sash is Cortizo's tilt-and-turn / casement aluminium window system on a 70 mm thermally broken frame. The 'hidden sash' detail means the opening sash sits concealed within the frame depth, so a closed window reads as a single fixed glass panel without the visible step where a standard casement sash meets the frame. Used on premium contemporary projects where the architectural priority is the cleanest possible elevation.
What is a tilt-and-turn window?
Tilt-and-turn gives two opening modes from a single handle. Turning the handle 90° lets the top of the sash tilt inwards for secure ventilation — the window is open but not hinge-clear so it can't be reached. Turning the handle 180° unlocks full hinge function so the sash opens fully — useful for cleaning the outside glass from inside (relevant on upper floors) or for fire-escape access. The function is standard on Cor 70 Hidden Sash.
What U-values do Cortizo Cor 70 windows achieve?
Cor 70 Hidden Sash delivers excellent whole-window U-values when paired with the right glazing spec. With double-glazed Low-E units the whole-window Uw lands in the 1.2-1.4 W/m²K range — comfortably exceeding Approved Document L's 1.4 W/m²K maximum. With triple-glazed Low-E units and Class 4 air permeability the system achieves BFRC A++ — the top of the BFRC scale. Specific Uw is calculated per opening at quote stage.
How does Cor 70 Hidden Sash compare to Schuco AWS aluminium windows?
Both are premium aluminium casement systems on a 70 mm frame. Cortizo Cor 70 Hidden Sash's distinguishing feature is the concealed-sash detail — a closed casement reads as a single fixed glass panel. Schuco's AWS family includes AWS 70.HI (workhorse with 117 mm sightline + 52 mm glazing capacity), AWS 70 SC Slimline (architectural slim 63.5 mm sightline) and AWS 70 Tilt-and-Turn outward-opening. Where the brief is open, we walk you through both at the survey stage. Side-by-side: /blog/cortizo-vs-schuco.
Are Cortizo Cor 70 windows Secured by Design?
Yes — Secured by Design configurations are available on Cor 70 Hidden Sash opening profiles. SBD is the UK police-approved security spec, recognised by Hiscox, Chubb, AIG and other premium home insurers. PAS 24:2022 certification is standard; SBD adds specific hardware and laminated-glass combinations on top.
Are Cortizo aluminium windows energy efficient?
Yes. Cortizo's thermally broken Cor 70 Hidden Sash paired with Class 4 air permeability (BS EN 12207, the maximum) and triple-glazed Low-E units reaches BFRC A++ — the highest available BFRC rating. Even with standard double-glazing the whole-window Uw comfortably exceeds Approved Document L's 1.4 W/m²K maximum for replacement windows. The 70 mm thermal break separates the cold outside metal from the warm inside metal so condensation on the inside frame is minimised.
Can I get Cor 70 windows in any RAL colour?
Yes — full RAL palette plus anodised finishes (champagne, bronze, dark grey, black) and dual-colour configurations (one finish inside, a different one outside). Aluminium colour stability comes from the powder-coat or anodising process, so dark colours and bold finishes don't fade or peel over decades.
Other Systems We Install
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