Aluminium Heritage Windows: Slimline Steel-Look Guide
Aluminium heritage windows are thermally broken aluminium frames designed to replicate the exact appearance of original 1930s Crittall steel windows. They use slim 58-60 mm sightlines, stepped edges, and mechanical joints to match the industrial aesthetic while meeting current Building Regulations Part L. These windows solve the biggest problem for owners of listed buildings, conservation areas, or 1920-1950 period properties: you keep the authentic look but gain modern performance without planning rejection.
Most original steel windows now suffer 40-60% heat loss, rust through at the corners, and fail basic security tests. Replacing them with standard uPVC or thick aluminium usually gets refused by conservation officers. Aluminium heritage systems such as Alitherm Heritage, Smart Heritage 47, or Origin Artisan pass Article 4 directions because the profile depth stays under 62 mm and the glazing bars remain under 24 mm wide.
This guide covers every practical detail you need before ordering: exact specifications, real UK pricing (2025 figures), installation pitfalls in period properties, and proven case studies from recent projects.
What Exactly Makes a Window “Heritage” in Aluminium?
Heritage aluminium windows are not just any slim aluminium casement. Manufacturers engineer them with four key features that standard aluminium lacks:
- Sightlines between 58-60.5 mm (standard aluminium starts at 78 mm)
- True divided glazing bars (not stuck-on fake bars)
- Stepped outer frame and vent edges that mirror steel
- Mechanical corner cleats instead of welded joints for the authentic look
According to the Steel Window Association, over 70% of pre-1950 metal windows in the UK now need replacement. Aluminium heritage profiles have become the only compliant material that satisfies both conservation officers and Part L U-values (typically 1.4–1.6 W/m²K with double glazing).
The Real Benefits You Actually Notice After Installation
Thermal performance improves immediately. Independent tests on Alitherm Heritage windows show a whole-window U-value of 1.4 W/m²K with standard 28 mm double-glazed units containing argon and warm-edge spacer. That cuts heat loss by 65% compared with single-glazed steel.
Maintenance drops to almost zero. Powder-coated aluminium carries 25–40 year guarantees against cracking or fading (Qualicoat Seaside class for coastal areas). You never paint again, unlike timber that costs £400–£600 per window every 7–10 years.
Security reaches PAS 24 and Secured by Design as standard. Multi-point espag locks plus internal beading make forced entry take over six minutes – the police benchmark for deterrence.
Sound reduction reaches 36–40 dB Rw with acoustic laminate, perfect for period homes now on busy roads.
Popular Configurations That Work in Real UK Homes
- Fixed lights with horizontal glazing bars – cheapest option for large Art Deco panels
- Top-hung vents with peg stays – matches 1930s council house style
- Side-hung casements opening to 90° – standard for Victorian and Edwardian terraces
- French casements (no fixed mullion) – popular in 1930s semis
- Stacked modules with drip bars – essential for tall warehouse or school conversions
Most suppliers offer over 200 RAL colours. The most requested combination remains RAL 9005 matt black externally with RAL 9010 pure white internally.
Current 2025 UK Pricing (Supply Only vs Supply & Install)
Single casement 600 × 1200 mm – £780–£940 supply only Same window supplied and installed – £1,180–£1,420 Large fixed panel 1200 × 2100 mm – £1,100–£1,350 supply only Typical 1930s bay (5 units) – £5,800–£7,200 fully installed
Prices dropped 12% since 2023 because of increased competition between Origin, Smart, Sheerline, and AluK heritage ranges. Ten-year insurance-backed guarantees come as standard.
How to Get Planning Approval in Conservation Areas
Submit the manufacturer’s heritage brochure page showing sightline drawings and joint details. Include a 1:1 printed section (most councils now accept digital). State the existing windows are beyond economic repair – attach a structural report if the steel has rusted through. Reference the Crittall window entry on Wikipedia to prove the visual precedent.
95% of applications using Alitherm Heritage or Origin Artisan get approved first time when the paperwork includes proper sections.
Installation Day – What Actually Happens
Professional teams remove one window at a time to keep the house secure and weather-tight. They pack the new frame 5–8 mm off the brickwork reveal and use compriband tape plus low-modulus silicone. Stacked units need stainless drip bars aligned perfectly or water sits on the transom – a common leak cause on cheap jobs.
A three-bedroom 1930s semi takes three to four days for twelve windows.
Maintenance Schedule That Keeps Them Perfect
- Week one after install – check weeps are clear
- Every spring – wash with warm soapy water
- Every autumn – light oil on hinges and locks
- Every five years – inspect gasket compression
That’s it. No sanding, no priming, no repainting.
Three Real Projects from 2024–2025
- Manchester 1930s semi – replaced 14 rusted Crittall with Origin Artisan black. Energy bill dropped £220 per year. EPC moved from E to C.
- Brighton listed Art Deco mansion block – 42 windows using Smart Heritage 47. Planning approved in 28 days. Residents report 60% less traffic noise.
- Leeds warehouse conversion – 4.2 m high stacked units in Sheerline Heritage. Passed building control first visit because drip bars were factory-fitted aluminium Heritage Window
Aluminium heritage windows are now the default choice across the UK for any period property that originally had metal windows aluminium Heritage Window. They look right, perform better than new steel ever could, and cost less in the long run.
Need exact sizes priced for your house? Drop the dimensions in the quote form below and we’ll send current 2025 pricing within one working day – no sales calls.
