When it comes to high-end home renovations in Windsor, Ascot, and across London, the demand for slimline aluminium windows has never been higher. Homeowners are increasingly moving away from bulky frames in favour of “more glass, less frame.” This aesthetic is particularly popular for those looking to replicate the classic industrial steel-look or to create a minimalist, modern façade.
At Inspired Glazing, we frequently get asked to compare two of the industry’s most respected systems: the Reynaers SL68 (SlimLine 68) and the Cortizo Cor 70 Hidden Sash. Both offer exceptional aesthetics and performance, but they cater to slightly different project requirements and budgets.
This guide breaks down the technical specifications, aesthetic differences, and performance metrics of both systems to help you decide which is the right fit for your property.
Reynaers SL68: The British “Gold Standard”
The Reynaers SlimLine 68 is widely considered the gold standard for high-end residential projects in the UK. Designed specifically to meet the aesthetic and functional needs of British homes, it is the go-to system for aluminium windows near me when the client prioritises brand heritage and a “precise fit.”
Designed for the UK Market
Unlike many European systems that focus heavily on inward-opening “tilt and turn” functionality, the SL68 is a dedicated outward-opening casement system. This is crucial for properties in Windsor and Maidenhead, where traditional UK window layouts dominate. It allows for a familiar operation while providing a significantly slimmer profile than standard aluminium or uPVC systems.
The Steel-Look Specialist
If you are looking for a “steel-look” replacement to replicate original Crittall-style windows, the SL68 is unmatched. Its ultra-slim frames and the ability to add decorative astragal bars allow it to maintain the character of period properties while offering modern energy rated windows performance.
Technical Precision
- Frame Depth: 68mm.
- Weather Performance: Industry-leading air, wind, and water resistance, tested to rigorous UK standards.
- Security: Fully PAS 24 certified with multi-point locking as standard.
- Thermal Performance: Excellent insulation values that comfortably exceed current UK Building Regulations.
Cortizo Cor 70 Hidden Sash: The Minimalist Challenger
While Reynaers is the established premium choice, Cortizo has gained massive popularity for its innovative design and highly competitive price point. The Cor 70 Hidden Sash is a specific variant designed to offer the most “frameless” look possible.
The “Hidden Sash” Concept
The standout feature of this system is that the sash (the part of the window that opens) is completely concealed behind the outer frame. From the outside, an opening window looks identical to a fixed pane. This creates a uniform, symmetrical appearance across the entire building façade.
Performance at a Better Price
Cortizo offers a similar minimalist aesthetic to Reynaers but often at a slightly lower price point. For property developers and homeowners in Ascot and Sunningdale working on larger extensions or new builds, this can lead to significant cost savings without sacrificing the high-end look.
Key Considerations
- Visible Sightline: An incredible 66mm visible section.
- Inward Opening: The Cor 70 Hidden Sash is primarily a tilt-and-turn system. While this offers great ventilation and easy cleaning from the inside, it is important to consider how inward-opening windows might interact with your curtains or blinds.
- Thermal Performance: Capable of achieving U-values as low as 1.0 W/m²K with the right glazing specification, making it one of the most efficient aluminium vs uPVC options on the market.
Direct Comparison: How They Stack Up
When choosing between these two systems for your project in Windsor or London, it helps to see the data side-by-side.
Why Location Matters: Windsor, Ascot, and London
For our clients in Windsor and Maidenhead, the choice often leans toward the Reynaers SL68. The reason is simple: heritage. Many properties in these areas have traditional aesthetics where an outward-opening casement feels “right.” The SL68 allows you to upgrade your home’s thermal performance and security without making it look like a modern office block.
Conversely, in London and Ascot, where we see more contemporary extensions and “glass-box” style architecture, the Cortizo Cor 70 Hidden Sash is a frequent favourite. Its ability to create a completely flat, uniform exterior is perfect for high-end minimalist designs where the goal is to maximize natural light.
The Inspired Glazing Difference: Precise Fit, Every Time
Regardless of the system you choose, the performance of a slimline window depends entirely on the quality of the survey and the installation. At Inspired Glazing, we specialize in the “precise fit.”
Our process begins with an on-site survey where we take accurate measurements to ensure that the slim sightlines are maintained and the thermal seals are perfectly weather-tight. We understand the technical nuances of both Reynaers and Cortizo systems, ensuring that your investment delivers long-term performance.
Clean Workmanship
We pride ourselves on professional conduct and “clean workmanship.” Our installers respect your home, ensuring a tidy workspace and a flawless finish on every project. Whether we are installing a single window in Maidenhead or a full house of aluminium systems in West London, our commitment to quality remains the same.
Frequently Asked Questions
Which window is better for energy efficiency?
Both systems offer excellent thermal performance. However, because the Cortizo Cor 70 Hidden Sash can accommodate thicker glazing units and features a larger thermal break, it can technically achieve slightly lower U-values (better insulation) in certain configurations. For most homeowners, both will exceed the requirements for a comfortable, warm home.
Are slimline windows secure?
Yes. Both the Reynaers SL68 and Cortizo systems are tested to PAS 24 standards. They feature multi-point locking systems and high-strength aluminium frames that are much harder to breach than traditional timber or older uPVC systems.
Can I have these windows in any colour?
Absolutely. Both systems are available in a vast range of RAL colours. While Anthracite Grey (RAL 7016) and Black are the most popular for the minimalist and steel-look aesthetic, we can provide bespoke powder-coated finishes to match your specific interior or exterior design.
Verdict: Which Should You Choose?
- Choose Reynaers SL68 if: You live in a traditional or period property, you want the classic UK outward-opening operation, and you are looking for the absolute best in brand reliability and steel-look aesthetics. It is the definitive choice for Windsor windows.
- Choose Cortizo Cor 70 Hidden Sash if: You are building a modern extension or new home, you want the slimmest possible “all-glass” appearance from the outside, and you are looking for high-end performance at a more accessible price point.
Ready to Upgrade Your Home?
Choosing the right windows is a significant decision for any property owner. At Inspired Glazing, we provide clear, no-obligation quotations and professional advice tailored to your specific project.
Request a call back or call us today to discuss your project.
Phone: 01753 965 005
Service Areas: Windsor, Ascot, Sunningdale, Maidenhead, and all 32 London boroughs.