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Flush Aluminium Windows


Klosen / Aluminium Windows / Flush Aluminium Windows

entrance hall with wood beams front door and curtain wall
new build house with mix of design styles


Flush Aluminium Windows offer a smooth, flat exterior that mimics the style of a traditional casement window. The result is a sympathetic upgrade to your contemporary or heritage property, with many added performance benefits.

At Klosen, we provide over 25 years’ experience in supplying and installing the highest quality contemporary aluminium windows and doors for homes and businesses. Working in and around Peterborough, we deliver exceptional customer service and a 10 year guarantee.

Partnering with a range of leading manufacturers, you’ll benefit from having more options so you can choose the exact design you want for your project.

Ready to get your project underway? We don’t just supply, we also install and ensure a seamless renovation from start to finish.

Get your free quote from Klosen today or download a brochure.

What Are The Benefits of Aluminium Flush Windows?

With flush windows, you can create a flawless exterior that also delivers the thermal efficiency you’d expect from a modern home.

Designed for top or side hung opening-out windows, they provide a clean, smart look that’s naturally more appealing. You can recreate the look of a traditional casement window, whilst enjoying the insulation benefits. Keep your home resistant against the elements and boost energy efficiency to keep your heating costs down.

Get your free quote today or download a brochure.

Brands We Work With

We work with a range of brands at the forefront of innovative design, including SAS and Cortizo. These manufacturers are dedicated to pairing excellent energy efficiency with contemporary, bespoke design.

Discover more about each brand below or download a brochure for further information.

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Cortizo Logo
Senior Architectural Systems Logo

Our Customer Reviews

Great Price & Quick Delivery

This company have been amazing and came to our rescue when another company let us down repeatedly over a period of 4 months during our building work. We got a great price, a quick delivery time and the same product but this time with lovely fitters who knew exactly what they were doing. Now we will will have a warm house for christmas HOORAY !! We went for 3 large sliding doors and the quality of the product is excellent . Many thanks to Audrey Cieran and the team I would recommend highly
- Esther Young


Delighted with the product and the service provided by Klosen. The installation team were excellent and very helpful.
- Sara Hyem

Very Happy

We’ve been very happy with the work Klosen recently completed for us. They installed a variety of windows and sliding doors for us on our new build project. All of the information we requested early on was provided promptly and they were great with our architect. Very happy with the end result and the colour they helped us chose.
- Sarah Munton


Spanish manufacturer Cortizo has been leading the way in contemporary windows and doors since 1972. Working exclusively with aluminium, all of their designs combine excellent function and form. You’ll benefit from fantastic U-values as low as 1.0 W/m2K. Cortizo windows have excellent thermal insulation, reducing your energy bills.

By beautifully combining function and form, you can get luxury windows that look sophisticated and deliver high performance.

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modern house and gravel drive

Cortizo Specifications

Security test:  British Security Certification PAS 24

Transmittance: Uw ≥ 1.0 (W/m2K)

Acoustic insulation: Rw up to 45 dB

Water tightness: Class E1200

Air permeability: Class 4

Wind resistance: Class CE 2400

10 Year Guarantee

We offer a 10 year guarantee on all aluminium profiles and 25 years for the powder coating element

Thermal Efficiency

Stay warm in the winter and cool in the summer whilst cutting down on energy bills

Complete Flexibility

Our team are flexible throughout the entire process, including the design and installation of windows

25+ Years Experience

Klosen have over 25 years experience working with designers, architects and homeowners

Senior Architectural Systems

British manufacturer Senior Architectural Systems (SAS) has become one of the nation’s top suppliers of contemporary windows. With an expanded polyurethane thermal barrier, their designs provide exemplary thermal comfort and energy efficiency for your property.

Since 1991, the brand has been pioneering elegant designs that are the perfect match for your property design goals. Today, they are one of the country’s leading suppliers of luxury flush aluminium windows.

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Newly build house with mixed architecture

Senior Architectural Systems Specifications

Typical sizes:
Width (mm)

Height (mm)
x 1400

Thickness: 28mm – 44mm

Air Permeability: 600 Pa
Water Tightness: 600 Pa
Wind Resistance: 1600 Pa

Residential CEN Standard:
1230 x 1480:
28mm Double Glazed Unit: 1.5 W/m2K
44mm Triple Glazed Unit: 1.1 W/m2K

Tested to PAS24, BS6375-1, BS6375-2 and BS6375-3

Typical sizes:
Width (mm)

Height (mm)
x 1500

Thickness: 28mm – 50mm

Air Permeability: 600 Pa
Water Tightness: 600 Pa
Wind Resistance: 2400 Pa

Residential CEN Standard:
U-values as low as 0.73 W/m2K

Tested to PAS24, BS6375-2 and BS6375-3

Colour Options

With a choice of double and triple-glazing and over 200 RAL colour options with a range of finishes, the possibilities are endless. There is also the option to colour match or add a metallic, textured or anodised finish. Our brands offer a state of the art powder coating that won’t corrode over time. You can even choose a dual finish, with different colours on the interior and exterior frame.

It’s all part of ensuring we can offer a truly bespoke finish for your unique home project. Whether you want to keep things simple or choose something a little more striking, the choice is yours.

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This Dutch-inspired barn project included windows installed by the team at Klosen. The South-Lincolnshire-based couple selected windows designed and manufactured by Cortizo with great results. It’s an impressive industrial-chic facade that delivers optimum insulation, light and views for their upper floor.

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Areas We Cover

We typically cover areas across a 60 mile radius from our Lincolnshire-based premises in Market Deeping. If you’re based in Lincolnshire, Cambridgeshire or London, get in touch with our team.

From Peterborough and Stamford to Camden Mews, we’ve worked on a wide range of period and contemporary property designs.

From initial design and planning, through to installation, we ensure our customers are completely happy with the development of the project. Our hassle-free service has earned us 5-star reviews from many of our customers.

Request a free quotation today and contact us to find out more about our luxury aluminium doors and windows in Peterborough and Cambridgeshire today.

Why Choose Klosen?

  • Over 25 years of experience
  • Five-star reputation
  • 10 year guarantee

No project is too big or small for our team! Our experience extends to high-profile projects, including a property featured on Grand Designs and the ABBA Arena in London.

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Do I need a survey?

A survey is highly recommended. That way our window installation specialist can offer the best advice for your project and ensure you’re getting exactly what you want.

What is the lead time for your flush aluminium windows?

Lead times can vary, but are around 5 – 6 weeks for both supply and installation of most of our aluminium windows and doors. Our team will always keep you updated.

How do I get a quote?

It’s simple – fill out our request a quote form and a member of our team will be in touch to discuss your requirements with no obligation.

Get in touch with us today to receive your free quotation!