Discover the Internorm KF 520 uPVC-aluminium window with an invisible sash for maximum light & revolutionary I-tec Secure (RC 3).
The KF 520 combines cutting-edge design with advanced performance, offering a sleek, frameless aesthetic that maximises natural light. From the outside, the sash is virtually invisible—creating a smooth, minimalist appearance that closely resembles fixed glazing.
Beyond visual appeal, the KF 520 leads in security with Internorm’s I-tec Secure system. This innovative technology uses integrated locking flaps that press into the frame on all sides when closed, achieving burglary protection up to RC3—making it one of the most secure windows in its class.
With Uw values of up to 0.63 W/m²K and sound insulation up to 46 dB, the KF 520 ensures optimal energy efficiency and acoustic comfort. It's the perfect choice for those seeking contemporary style, enhanced daylight, and complete peace of mind.
Features:
Benefits:
Homeowners looking for modern windows with a focus on maximising natural light and providing high levels of security.
Working closely with architects, builders, and homeowners, we’ve delivered systems that combine thermal efficiency, modern aesthetics, and long-term durability—across private residences, sustainable developments, and architect-led designs.
The renovation project was successfully completed on schedule, surpassing initial insulation and energy efficiency goals by an impressive 70% and delivering a sleek, contemporary finish.
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Explore Harriet's Lodge, a House of the Year nominated new build in Southampton, featuring AT-ECO timber-aluminium windows, Passive House standards, and smart home integration.
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Explore Charlie Luxton's stunning Passive House new build in Beanacre, Oxfordshire, achieving an A++ energy rating with AT-ECO timber-aluminium windows, MVHR, and smart home tech.
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Explore Stockhouse Farm, award-winning A++ Passive House terraced homes in Surrey designed for modern families, blending traditional design with cutting-edge energy efficiency.
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Explore The Cook's House: a contemporary detached house in Gloucestershire blending classic architecture with sustainable design and AT-ECO timber-aluminium windows.
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Explore Blackwood, an award-winning Passive House in urban Bedfordshire ('Best Self Build' 2023) featuring AT-ECO triple glazing, solar blinds, and airtight construction for max energy efficiency.
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Explore this stunning coastal new build in Bexhill on Sea, East Sussex, featuring AT-ECO high-performance triple glazing and marine-grade finishes for resilience & maximised views.
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See the Squirrels Chase project: a home transformation in Bromley enhancing thermal performance, comfort, & curb appeal by replacing windows & doors with AT-ECO Internorm systems.
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Explore Hunters Hill, an exceptional Passive House in Guildford showcasing sustainable living with AT-ECO high-performance windows, solar panels, Tesla batteries, and Loxone smart home tech.
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Explore Lower Priory Farm: a luxurious new build in Stanmore, London, blending contemporary design with sustainability and featuring expansive glass & AT-ECO timber-aluminium windows.
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Explore Chalkwood: a modern coastal Passive House in St Margaret's at Cliffe, Dover, featuring AT-ECO windows/doors, marine-grade finishes, and stunning sea views for sustainable living.
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Explore Tanglewood: a unique Passive House in St Margaret's at Cliffe, Dover, recessed into the landscape, blending design with nature & AT-ECO high-performance windows for a sustainable retreat.
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Explore Blenheim Terrace: a collection of three luxury townhouses in London's St John's Wood conservation area, blending modern design with traditional charm & AT-ECO high-performance windows.
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Explore the Notting Hill Gate South Block refurbishment in London, blending modern Schüco curtain walling with 1950s architecture for enhanced energy efficiency & style.
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Explore Slips House: an innovative Paragraph 80 home in Hertfordshire's AONB, integrated into the landscape with a grass arch & Reynaers systems for outstanding sustainability.
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Explore 'Forty': a sustainable London family home featured on Grand Designs, showcasing AT-ECO high-performance triple glazing & Passive House principles for urban living.
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Explore Black Barn Studios: an award-winning sustainable workspace in Oxfordshire, a repurposed barn achieving Passivhaus principles with AT-ECO high-performance windows & exceptional airtightness.
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Explore Market Place: a luxury apartment development in Henley-on-Thames, combining rustic charm with contemporary living & AT-ECO high-performance windows/doors.
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Explore Skyridge: an award-winning sustainable contemporary home in Surrey Hills with an A-96 energy rating, featuring AT-ECO high-performance glazing & smart systems.
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See the Petersfield renovation in East Hampshire, enhancing comfort & style with AT-ECO Internorm windows & doors, including integrated blinds, for improved energy efficiency.
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Explore Lamorna: a sensitive 1960s Cotswold renovation blending contemporary design with conservation needs, featuring AT-ECO high-performance glazing & curtain walling for a low-energy home.
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Explore the transformation of Market Road: a former London printworks into a sustainable 45,000 sq ft office HQ, blending modern design with industrial heritage using AT-ECO Reynaers systems.
View the projectExplore detailed material comparisons, tailored installation advice,
and practical maintenance tips to keep your windows and doors performing at their best.
We’re excited to introduce the HF 420 to our premium range of timber/aluminium window systems. Perfect for both residential and commercial projects, the HF 420 is now available to explore at our Brasted showroom.
Yes, we recommend booking an appointment to ensure personalised service and availability. You can schedule your visit by filling out our contact form or emailing us at [email protected].
During your visit, our team will guide you through our range of premium window and door systems. We’ll answer your questions, help you explore customisation options, and assist in finding the perfect solution for your project.
Absolutely! Bringing your project plans or drawings can help our team better understand your needs and provide tailored recommendations.
Our knowledgeable team is here to help. Whether you need advice on materials, styles, or energy efficiency, we’ll guide you through the process and ensure you make an informed decision.
Our experienced team provides bespoke window designs and precision installations, ensuring every detail complements your architectural style.
