Slim, authentic sightlines
Signature slim sightlines and attractive contours make it the ideal choice for heritage building conservation areas where building regulations demand a like-for-like replacement.
- Crittall Steel
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What Are Alitherm Heritage Windows?
Alitherm Heritage windows are the best-known and best-selling aluminium windows with a steel-look style, designed by Smart Systems — the UK’s largest aluminium systems company.
Taking inspiration from traditional steel windows, Alitherm Heritage features signature slim sightlines and attractive aesthetic contours, coupled with polyamide thermal break technology — giving enhanced thermal performance and narrow sightlines.
The result? A window that looks exactly like the original steel frames your property demands — but performs like a modern, thermally efficient aluminium system. No rust. No repainting. No compromises.
At Lightfoot Windows, we supply and install Alitherm Heritage across London and the South East, with the full range on display at our London showroom. Come and see them in person before you commit.
What Are Alitherm Heritage Windows?
Outstanding thermal performance
Thanks to a polyamide thermal break within the slim frame, the Alitherm Heritage can provide an overall Uw-value of 1.5 when paired with high-performance double glazing — and the thermal break is 160x better than steel.
Versatile window styles
Available in fixed-pane, sash, top-hung, side-hung casement, pivot, and tilt-and-turn configurations.
Perfect for Listed Buildings & Conservation Areas
Getting planning approval on a period property is never straightforward. The wrong window choice can stall a project or lead to costly rework.
Alitherm Heritage features signature slim sightlines and attractive contours, making it the ideal choice for heritage building conservation areas where building regulations demand a like-for-like replacement.
Even listed buildings have been refurbished with this brand of steel-look windows, and many London Boroughs approve the product, as well as the Home Counties and Wales.
That’s a significant advantage — especially if your project is in London, where so many homes were originally fitted with steel windows. Throughout London, Alitherm has enabled many buildings to be modernised and converted to dwellings or new offices.
We understand these projects inside out. Our team will guide you through the right configuration, glazing options, and colour finish to satisfy your local planning authority and exceed your expectations.
Colours, Glazing & Customisation
No two heritage projects are the same, and your windows shouldn’t be either. Alitherm Heritage gives you genuine flexibility:
- Dual-colour options — a heritage tone on the outside, a crisp contemporary finish inside
- Full RAL palette — from classic anthracite and black to bespoke metallic and textured finishes
- Glazing options include double and triple glazing, as well as obscure, laminated and toughened glass, with glazing thickness ranging from 24mm to 36mm.
Every window is made to measure for your opening — no off-the-shelf compromises.
See Alitherm Heritage at Our London Showroom
Visit our London showroom to appreciate the stunning aesthetics of our authentic products up close. We feature our slim aluminium range, showcasing the external Alitherm Heritage profiles.
Seeing the slim sightlines, hardware choices, and finish quality in real life makes all the difference — especially for a heritage project where the detail truly matters.
Ready to get started? Contact our friendly team today for a free, no-obligation quote. We’ll handle everything from survey to installation, with precision and care at every stage.
Installation & Warranty
A meticulous survey-to-handover process ensures accuracy, finish quality and seamless integration with surrounding fabric. Our experienced installers coordinate with your contractor or architect to achieve clean lines, correct tolerances and reliable sealing. Products are supported by insurance-backed guarantees for long-term peace of mind—reflecting our commitment to performance and aftercare.
Customisation Options
Explore our extensive customisation options for aluminium windows, including a variety of colours, hardware selections, and downloadable resources for detailed information.- Colours
- Hardware
- Downloads
Colours
Popular Colours
Our aluminium windows are available in a vast array of frame colour options, including classic black and contemporary hues. The iconic black steel finish is not only visually stunning but also seamlessly complements a range of architectural styles, ensuring a stylish and cohesive look for your property.
Anthracite Grey
Black
White
Hardware
Hardware Options
Select from an array of hardware options for your aluminium products, including durable hinges and locks designed for optimal functionality. Our choice of high-quality finishes provides both aesthetic appeal and reliable security features for your windows.
Standard Handle
Bulb End Handle
Monkey Tail Handle
Art Deco Handle
Bulb End Peg Stay Handle
Downloads
Downloadable Resources
Access our downloads section below to discover vital specifications and design options for our aluminium windows, engineered to offer exceptional performance and modern style for both residential and commercial applications.
Latest Projects
Frequently Asked Questions
We address some of the most frequently asked questions regarding our aluminium windows, providing you with essential information to help you make informed choices for your project.
Is aluminium better than uPVC for windows?
If you want ultra-slim sightlines, larger panes and long-term stability, aluminium is usually the better choice. Modern thermally-broken frames achieve excellent energy performance with double or triple glazing, won’t warp or discolour, and can be powder-coated in any RAL colour. uPVC can be more budget-friendly, but aluminium wins for strength, design flexibility and lifespan.
Are aluminium windows bad for condensation?
No. Condensation is caused by humidity and temperature differences, not the material itself. Today’s aluminium systems use a polyamide thermal break and warm-edge glazing to keep internal surfaces warmer, helping to reduce condensation risk. Good ventilation (trickle vents/extractor fans) and consistent heating are also important.
What are the benefits of aluminium windows?
Aluminium windows offer exceptional durability, low maintenance, and energy efficiency. This makes them a popular choice in the UK, with their strength allowing for slim frames and larger panes that let in maximum natural light.
Are aluminium windows energy efficient?
Yes, our aluminium windows feature thermally broken profiles that provide exceptional energy efficiency, helping to keep your home warm and lowering heating costs.
Can I customise the colour of my aluminium windows?
Absolutely! Our aluminium windows are available in a variety of RAL colours, allowing you to choose the perfect frame colour to complement your property’s aesthetic.
How do I maintain aluminium windows?
Our aluminium products require little maintenance. Regular cleaning will keep them looking great while preventing moisture build-up or condensation issues, ensuring long-lasting performance.
Are aluminium windows secure?
Yes, our windows come with high-quality locks and robust construction, providing peace of mind with their superior security features, backed by excellent customer service.
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What our customers say
Despite being a small project by comparison, from start to finish our project has been executed with precision, promptness and professionalism to deliver a thing if beauty which as we...
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Sharman & Phil
LOVE. LOVE. LOVE my windows and doors! They look amazing! 😍 Lightfoot Windows were a pleasure to deal with. Polite, helpful and informative. Plan to use them again for a...
Read more
Adiba Ghauri
Very efficient and thorough. Quick installation. Very helpful and friendly staff. My new Crittall windows are beautiful.
Read more
Susan Tuffy
I would like to thank the team at Lightfoot windows for supplying and fitting my new Crittal windows, from start to finish the service has been great and the product...
Read more
Lee
Excellent windows (Heritage Aluminium french doors). Our builder was impressed with the excellent quality and will be using again. Efficient fitting, fitted perfectly.
Read more
Sophia Barlow
I am very pleased with the Crittall windows as supplied and fitted by Lightfoot. I visited their showroom and discussed the requirements, and these were met in full. From the...
Read more
David SC
Probably one the best experiences we've had with a building contractor/supplier. We went to the showroom where we were given all the information we needed and shown the various options...
Read more
Paul Phillips
Lightfoot supplied & installed a steel Crittal arch for an internal opening. Both the design and install process was very professional and we are delighted with the product. Would highly...
Read more
Richard Simpson
We have used Lightfoot Windows on two occasions now, and both times their service has been exemplary. The products we purchased are also of a very high quality and we...
Read more
Martin French
I cannot recommend Lightfoot highly enough. I used to run a business, and the sheer pleasure and relief of being communicated with properly and courteously means a lot. It’s rare...
Read more
Catherine C
So happy to have found Lightfoot Windows who supplied fire rated Crittall doors and screens. Great showroom full of inspiration. Unhurried great advice given, quote and contract really streamlined and...
Read more
Torsten Mansson
Despite being a small project by comparison, from start to finish our project has been executed with precision, promptness and professionalism to deliver a thing if beauty which as we had hoped brings the outside in - our garden by day and the stars by night. We had the pleasure of Reese (still amazed at the price of a cup of tea and a bed for the night in Driffield) and Brad installing our curtain wall, accounting for the vagaries of an old property on a freezing cold day. Marcin as surveyor/project managing was careful and considered in his surveying and measuring. Clear and concise in his instructions to our builder. Paul's input at the design and acquisition stage ensured there was accurate representation of what we wanted. Praise indeed from an aircraft design engineer used to working to a "thou of an inch". We wouldn't hesitate to recommend investing in this company and its products.
Sharman & Phil
LOVE. LOVE. LOVE my windows and doors! They look amazing! 😍 Lightfoot Windows were a pleasure to deal with. Polite, helpful and informative. Plan to use them again for a new internal window very soon. Would definitely recommend. Thank you guys !
Adiba Ghauri
Very efficient and thorough. Quick installation. Very helpful and friendly staff. My new Crittall windows are beautiful.
Susan Tuffy
I would like to thank the team at Lightfoot windows for supplying and fitting my new Crittal windows, from start to finish the service has been great and the product is first class. great value for money.
Lee
Excellent windows (Heritage Aluminium french doors). Our builder was impressed with the excellent quality and will be using again. Efficient fitting, fitted perfectly.
Sophia Barlow
I am very pleased with the Crittall windows as supplied and fitted by Lightfoot. I visited their showroom and discussed the requirements, and these were met in full. From the initial visit to the final fitting Lightfoot exceeded my expectations and I would unhesitatingly recommend them.
David SC
Probably one the best experiences we've had with a building contractor/supplier. We went to the showroom where we were given all the information we needed and shown the various options for our kitchen patio doors. We selected what we wanted and gave the dimensions and by the time we got home, there was a plan and an estimate in our inbox.
Paul Phillips
Lightfoot supplied & installed a steel Crittal arch for an internal opening. Both the design and install process was very professional and we are delighted with the product. Would highly recommend and I would certainly use them again for future products.
Richard Simpson
We have used Lightfoot Windows on two occasions now, and both times their service has been exemplary. The products we purchased are also of a very high quality and we are really happy with them. The surveyors and installers were careful, considerate and polite. We highly recommend Lightfoot Windows and will definitely use them again should the need arise.
Martin French
I cannot recommend Lightfoot highly enough. I used to run a business, and the sheer pleasure and relief of being communicated with properly and courteously means a lot. It’s rare these days. The windows and installation were excellent. Reece, Grant & Bradley were fantastic. Particularly as they were up against supply issues, parking restrictions not to mention Covid.
Catherine C
So happy to have found Lightfoot Windows who supplied fire rated Crittall doors and screens. Great showroom full of inspiration. Unhurried great advice given, quote and contract really streamlined and easy to understand. Service was excellent throughout visiting, ordering measuring up and installation. Special thanks to Daniel at the showroom, Reece Taylor for an excellent installation and finish. Really pleased with the product and service. Would not hesitate to recommend and will definitely use again in the future.
Torsten Mansson