Cor 70 Hidden Sash Windows
COR 70 HIDDEN SASH WINDOWS
Modern Aluminium Windows with a Frameless Look
Some windows draw attention to their frames. The Cortizo COR 70 does the opposite. Its Hidden Sash Windows design conceals the opening sash behind the outer frame, so from the outside, every window looks like a fixed pane of glass. Clean lines. More light. No visual clutter. At 4 Moon Windows, we supply and install Cor 70 Hidden Sash Windows Croydon homeowners trust for extensions, new builds, and full window replacements. Based in Thornton Heath, we serve Croydon and the wider South London area with precision-made aluminium windows backed by honest advice and careful installation.
Ultra-Slim 66mm Sightline
Maximum glass area and natural light, even with all concealed upgrades fitted.
Thermal Efficiency
A 35 mm polyamide thermal break delivers U-values as low as 1.0 W/m²K
PAS 24 Security
Tested to meet stringent UK security standards, with multi-point locking and robust security
Fully Concealed Hardware
Hidden hinges, hidden drainage channels, and the ARCH INVISIBLE
WHAT ARE COR 70 HIDDEN SASH WINDOWS?
What Makes Cortizo COR 70 Hidden Sash Windows Different?
What Are Hidden Sash Windows?
A traditional window shows two frames: the outer frame and the sash that opens. Hidden Sash Windows tuck the opening sash behind the outer frame. From the street, an opening window and a fixed window look identical. The result is a slim, uniform grid of glass across your whole elevation. Cortizo describes the COR 70 simply: it looks like a painting, but it's a window. With a visible sightline of just 66 mm, you get more glass, more daylight, and a sharper, more architectural finish than standard aluminium frames can offer.
Hidden Sash vs Flush Casement Aluminium Windows
Both styles aim for the same thing: a flat, flush face with no bulky step between frame and sash. Flush casement aluminium windows open outward and sit level with the frame. The COR 70 hidden sash goes a step further. It opens inward, hides the sash completely, and conceals the hinges, drainage, and even the handle. If your project calls for a minimalist, glass-first look, the hidden sash is the cleaner of the two styles.Many of our Croydon clients pair it with slimline sliding or bi-folding doors from the same Cortizo family.
Key Features of the Cortizo COR 70 Hidden Sash
The COR 70 Hidden Sash TB is engineered in Spain by Cortizo, one of Europe's leading aluminium systems companies. Here is what sets it apart:
- Ultra-slim 66 mm sightline. Maximum glass area and natural light, even with all concealed upgrades fitted.
- Fully concealed hardware. Hidden hinges, hidden drainage channels, and the ARCH INVISIBLE handle keep every surface clean and uninterrupted.
- Outstanding thermal efficiency. A 35 mm polyamide thermal break delivers U-values as low as 1.0 W/m²K, helping cut heat loss and energy bills.
- Excellent sound insulation. Acoustic reduction of up to 46 dB, ideal for homes near busy Croydon roads, tram lines, or flight paths.
- Large sash capability. Sash sizes up to 1300 mm x 2400 mm and weights up to 160 kg, so tall, dramatic glazing is no problem.
COR 70 SASH WINDOWS
Why Croydon Homeowners Choose Aluminium Sash Windows
Aluminium sash windows combine slim, strong frames with larger glass areas, making them ideal for Victorian terraces, 1930s semis and modern homes.Their durable powder-coated finish resists warping, rot, rust and fading, while requiring minimal maintenance.With inward-tilting sashes, you can also clean the outside glass safely and easily from inside your home.
Perfect for Extensions, New Builds, and Full Window Replacements
Cortizo Casement Windows were engineered as a direct replacement for tired timber and uPVC frames, which makes them ideal for upgrading older homes without structural work.
Get Your Free Cor 70 Hidden Sash Windows Quote Today
Ready to Transform Your Home with Cor 70 Cortizo?
Get your free, no-obligation quote today. Call us, WhatsApp us, or book a quick chat online — and see why homeowners across Croydon and London trust 4 Moon Windows for premium aluminium casement windows.
FAQ
Frequently Asked Questions
Yes, aluminium costs more upfront than uPVC — typically 20–40% more. But Cortizo frames last decades longer, need almost no maintenance, and add more value to your property. Over the lifetime of the windows, they usually work out as the better investment.
Very. Thanks to the 32mm thermal break, Cortizo casement windows achieve U-values from 1.0 W/m²K with double glazing and as low as 0.9 W/m²K with triple glazing. This meets and exceeds current UK Building Regulations and helps reduce heating bills noticeably.
In a standard casement, the opening sash sits slightly proud of the outer frame. In a flush casement, the sash sits perfectly level with the frame, creating a smooth, flat appearance. Flush casements are popular for period properties and premium modern designs; both offer identical performance.
Yes. Cortizo Casement Windows are tested to British PAS 24 security standards and fitted with multi-point locking systems. Combined with toughened or laminated glazing options, they provide excellent protection for ground-floor and street-facing windows.
You can choose from the full RAL colour palette — over 200 shades — plus anodised and textured finishes. Dual-colour options let you have one colour outside and another inside, so your windows match both your exterior and your interior style.
Yes. We’re based in Thornton Heath and install across Croydon, South London, and the wider London area. Contact us with your postcode and we’ll confirm coverage and arrange a free survey.