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Slimline Aluminium Windows


Klosen / Slimline / Aluminium Windows

A modern white house with slimline aluminium windows


Elegant and luxurious slimline aluminium windows are specially engineered to create stylish, modern and sophisticated spaces in your home. From your entranceway to your living areas and bedrooms, there’s a window for every room of your home.

What are Slimline Aluminium Windows?

Popular for their beautifully sleek design, durability and sustainability, Klosen’s aluminium windows are designed to bring natural light into your home, and with Slimline thin frames, you’ll benefit from an increased glazed area, sweeping views and excellent thermal efficiency.

With more than 25 years as experts in the industry, Klosen embraces technology, contemporary materials and innovation. It is our priority to provide the highest quality products that create beautiful living spaces, combining elegant design with specialist, secure fittings.

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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

Why Choose Slimline Aluminium Windows?

These windows utilise sleek frames that imitate the look and feel of original steel. They offer complete or partial glazing without the need to modify the nature of the property. This means our fittings slot seamlessly into your home.

Our slimline range brings a contemporary feel to your home. With minimal framing and larger glass panels, you can create a sanctuary by inviting in more natural light and optimising your views.

Despite their thin frames, these windows don’t compromise on durability, security or insulation. This makes them ideal for homes and other architectural projects.

Slimline windows require minimal maintenance and are built to last. With Klosen, you’ll receive our 10 year guarantee on all aluminium profiles, including slimline bifold doors, with the powder coating element guaranteed for an increased 25 years against corrosion.

Request a quotation to discuss your home’s unique characteristics and we’ll recommend the best design for your project. Introduce sustainability into your home with peace of mind and download our brochure today.

Who We Work With

We work with homeowners, builders, architects and business owners to help them install aluminium windows that fulfil their contemporary design specifications and sustainability goals.

Our long-lasting relationships with our customers is true testament to our reputable work, trusted by customers across Peterborough, Cambridgeshire, Lincolnshire and the surrounding areas.

Modern White House Project With Slimline Windows
Modern house with wood panelled round and glass room

Slimline Aluminium Windows Installers

Our slimline aluminium window installers provide an outstanding level of service. From initial designs through to completion, we ensure our customers are 100% happy with the development of the project and our professional team will keep you informed of progress.

We understand that the premium cost of a slimline sliding window means customers expect a flawless product that’s built to last. That’s why we only supply the highest-quality slimline aluminium brands, including Senior Architectural Systems.

If you want to create a complete, harmonious style throughout your home, we also provide slimline sliding doors. Request a quotation today from our friendly team.

modern house with curtain wall with two tall white planters

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

Window Manufacturers

We also supply a range of other aluminium window manufacturers including Cortizo – which made an appearance on Channel 4’s Grand Designs with a project in Lincolnshire.


They are a Spanish firm that was established in 1872 and have become leading manufacturers and designers of quality aluminium windows. Their range of windows work in any room of your home and excel and letting in the maximum amount of natural light.

Learn more about Cortizo windows and the styles they have available.

gravel driveway to new Dutch barn building

Senior Architectural Systems

We supply a range of windows from Senior Architectural Systems, including the following:


The AliVU casement window has been designed to meet current and future building regulations, with impressive U-values and thermal performances. Suitable for both commercial and domestic use, the AliVU casement windows come with a choice of vents to suit your design preferences.

Aluminium Series 2

The Aluminium Series 2 windows are perfect for commercial renovations and new builds.

Featuring signature slim sightlines and impressive U-values for improved thermal performance, these windows are engineered with current and future building regulations in mind.

We offer a range of glazing thicknesses available up to 44mm and a range of opening mechanisms to suit your design requirements

Senior Architectural System Brochure
Side aspect of modern house wood panelling and large windows

Where We Work

Based in Market Deeping in Lincolnshire, we work across a 60-mile radius from our premises. Popular areas include Peterborough, Cambridge, Lincoln and London. We install in urban and rural locations.

To enquire about any of our designs and how they could work with your property, contact our team today.

Who Are Klosen?

If you’re looking for aluminium windows and doors for your building or renovation project, we provide bespoke installations. Working with top brands from around the world, we can match your requirements and exceed your expectations on the finished result. With over 25 years of experience, we deliver a seamless experience from start to finish. We’ll get to know your design preferences and specifications.

To find out more about the products we supply, you can download our brochure.



Yes, these windows can come with a variety of shutter designs, including external roller-shutters and sunshades. We can discuss your requirements to ensure you’re getting the best shutters for your windows.


This will depend on how big the windows are and how many are being installed. However, we will always aim to estimate the time it will take to complete the installation of your slimline windows before work goes ahead.


With fully bespoke slimline window designs on offer, your dream windows can become a reality. We offer an exceptional range of slim frame window types including hybrid designs which are manufactured with a timber and aluminium composite, heritage style windows for period properties, and also offer a range of opening mechanisms and a selection of stylish frame colours. Whatever shape or size you require for your slimline window, we can deliver.


Yes, we can supply slimline windows for both commercial and residential properties.

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