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Aluminium Double Glazed Windows


Klosen / Aluminium Windows / Aluminium Double Glazed Windows

Double Glazed Window


Aluminium double glazed windows are an ultra-modern, practical-yet-stylish alternative to traditional PVC or wooden frames. Long-lasting, durable and beautiful to behold, our range of windows tick every box: we even offer heritage frames to suit historic properties.

So, whether you’re looking to modernise your home or add practicality and security while maintaining its quant, era-correct aesthetic, our lineup of aluminium windows has you covered.

As with our wider range of aluminium windows and doors, all are guaranteed for 10 years for total peace of mind.

Ready to learn more? Download a brochure to view the full range of products we offer or request your free quotation.

Why Choose Double Glazed Aluminium Windows?

Aluminium windows have plenty of benefits. They’re stunning to look at, for starters. Because the frames are stronger, they can be thinner. This means more glass and less frame, allowing more natural light into your property and giving your home an ultra-modern appearance. The durability of aluminium frames also allows them to be slimmer and flatter, resulting in a flush fit.

Another benefit of aluminium’s durability is its resistance to both the elements and intruders. Much tougher than wood and more resilient than PVC, aluminium windows can last for years and years – they won’t rot or crack.

A Vast Selection of Colours & Finishes

All of the windows we supply are available in a range of colours and finishes, so there’s certain to be one that suits your home or business premises. With either brand we supply, you can select from a handful of standard finishes or opt for a custom powder-coated finish in your choice of colour. Any shade in the RAL library is available to choose from, giving you hundreds of options!

Fitting aluminium windows to a property really can transform its appearance. Here are just a few of the installations we’ve recently completed:

Brands We Work With

If you want nothing but the best for your property, you’ve come to the right place. We don’t believe in compromising on quality here at Klosen, which is why we hand-pick the products we supply with great care. We work with two of the best brands in the industry, Cortizo and Senior Architectural Systems.

Each of these brands is renowned for their commitment to quality. Whether it be thermal efficiency, security or durability, a Senior Architectural Systems or Cortizo product is built to last and last. When you choose one of these windows, you’re truly making an investment in your property – and you could add value to it in the process.

All of the windows we supply are available in a range of colours and finishes, so there’s certain to be one that suits your home or business premises.

Download a brochure today to learn more.

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Senior Architectural Systems Logo
Cortizo Logo

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


A leader in its native Spain but renowned all over the world, Cortizo windows are undoubtedly among the most attractive you’ll find anywhere.

Established in 1972, the company specialises exclusively in the construction of aluminium windows and doors, giving it one focus: to produce the highest quality, most aesthetically pleasing products out there. Take one look at a Cortizo installation and it’s immediately evident that these windows are something special.

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modern house with wood panelling and sliding glass doors

Cortizo Specifications

Transmittance: Uw ≥ 1.0 (W/m2K)

Acoustic insulation: Rw up to 45 dB

Air permeability: Class 4

Water tightness: Class E1200

Wind resistance: Class CE 2400

Security test: PAS24 passed

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

Senior Architectural Systems

Since 1991, Senior Architectural Systems (SAS) has been on a mission to ‘revolutionise the UK’s fenestration industry.’ The company prides itself on producing top-quality, long-lasting products with outstanding thermal efficiency – and it never rests on its laurels. Continually innovating and improving upon its already world-class offering, SAS is one of the sector’s leading suppliers.

It was the first company to add a polyurethane foam thermal barrier to its aluminium windows and the first to offer powder-coated finishes with a no-quibble guarantee.

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double fronted house with feature stonework and driveway

Senior Architectural Systems Specifications

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:
1230 x 1480 28mm Double Glazed Unit: 1.24 W/m2K

Tested to PAS24, BS6375-2 and BS6375-3

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: 1.40 W/m2K

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


At the beginning of 2021, we embarked on one of our most exciting projects to-date. We were asked to supply and install Cortizo aluminium windows on this one-of-a-kind dream home, inspired by traditional Dutch barns. The build was documented on popular TV series Grand Designs.

So, no matter how ambitious (or straightforward) your project, you can rest assured that the team at Klosen have the skill to take it on.

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Areas We Cover

We’re located in Market Deeping, Lincolnshire, and generally serve areas within a 60-mile radius. Our installer can often be found across Cambridgeshire and Lincolnshire, but we also travel to London to complete projects on a regular basis. Our most popular locations include Peterborough, Bourne, Stamford and Huntingdon.

Why Choose Klosen?

  • Over 25 years of experience
  • Five-star reputation
  • 10 year guarantee on all work as standard
  • No project is too big or small
  • Experience working on high-profile projects, including a Grand Designs home and the ABBA Arena in London
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How energy efficient are aluminium double glazed windows?

This very much depends on the quality of the window unit. The items we supply come from renowned brands and have met stringent quality standards, ensuring optimal thermal efficiency all year round.

Can these windows rust or corrode?

No! These windows are guaranteed for a decade but should last much longer if they’re cared for; you won’t have to worry about them rusting, rotting or cracking over time.

Can aluminium windows be installed on a listed property?

Yes, although you will need to speak to your local authority to ask for permission beforehand: it’s up to them to decide whether or not your property can be fitted with aluminium frames.

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