Choosing between steel and aluminium windows for a period property is one of the most consequential decisions in any heritage renovation. The two materials share a visual language rooted in interwar and Art Deco architecture, but they differ in price, lead time, maintenance, and planning acceptance. This guide sets out the 2026 UK cost picture, compares performance and appearance, and helps you decide which material fits your property project.
Key Takeaways
- Heritage aluminium windows typically cost 30–50% less per opening than genuine steel windows of equivalent specification in 2026 UK projects.
- Steel windows generally suit high-budget, long-term prestige projects or listed buildings where only steel is acceptable. Aluminium windows are better for tighter budgets, larger property portfolios, or a busy lifestyle where low maintenance matters.
- Both modern aluminium and steel can be double glazed to meet current building regulations, with whole-window U-values around 1.4–1.6 W/m²K.
- Aluminium windows offer greater overall budget-to-performance value than steel for the majority of heritage-style renovations.
- Request a trade quote for bespoke heritage aluminium windows to get accurate pricing for your next scheme.
You can also see our curved alumiunium windows or flat iron windows on our sister site.
Heritage Aluminium vs Steel Windows: Which Is Best for Period Properties?
Most people reading this are weighing aluminium vs steel windows for a 1920s–1950s home, a warehouse conversion, or an Art Deco flat. The comparison matters because the two materials serve overlapping markets but at different price points and with different trade-offs.
How steel and aluminium compare at a glance:
- Steel excels in absolute authenticity, ultra-slim sightlines, and prestige on listed or high-value facades.
- Aluminium excels in cost, shorter lead times, corrosion resistance, and everyday practicality for whole-house upgrades.
Common scenarios include replacing old steel windows in a 1930s semi, upgrading single-glazed Crittall windows in a London maisonette, or specifying new windows for a 1920s-style extension on contemporary properties. The sections below cover detailed cost breakdowns, planning constraints for listed buildings and conservation areas, double glazing performance, and maintenance profiles.
How Much Do Steel vs Aluminium Windows Cost in 2026?
Real prices vary by size, glazing spec, and configuration, but ballpark guidance helps narrow your options before you request quotes.
Typical UK supply-and-install price ranges per opening
| Window type | Steel (fitted) | Aluminium heritage (fitted) |
|---|---|---|
| Small casement window | £1,200–£2,500 | £600–£1,800 |
| Larger French window or door | £2,000–£3,000 | £1,200–£2,000 |
| Bay windows or complex shapes | £2,000–£3,500+ | £1,400–£2,200 |
Source data from Checkatrade wider UK projects in 2026.
Aluminium is cheaper to purchase and install than steel across all categories. Steel windows generally cost more than aluminium windows because of the fabrication process, not the raw material price alone. Complex shapes, arched heads, or replica Art Deco grids increase costs for both materials, but the percentage gap stays broadly similar.
Worked example
A 1920s semi with eight original steel windows on the front elevation:
- Restore existing steel (single-glazed): 8 × £600 = approximately £4,800
- New thermally broken steel: 8 × £2,000 = approximately £16,000
- Heritage aluminium replica: 8 × £1,400 = approximately £11,200
Choosing aluminium saves around £4,800 on this building project versus new genuine steel. For a full house with more openings, the gap widens; a typical three-bed terrace might spend £16,000–£22,000 on aluminium heritage windows versus £30,000–£35,000 on steel.
Request a trade quote for bespoke heritage aluminium windows for accurate project pricing on your scheme.
Why Aluminium Heritage Windows Usually Cost Less Than Steel
The core price gap comes from fabrication methods, not raw material alone.
Aluminium heritage systems use mechanically jointed profiles and CNC-cut extrusions. Steel windows require skilled craftsmanship: welded corners, grinding, manual finishing, and multi-stage rust protection. That hand work adds hours per frame. Aluminium windows have lower production costs because the manufacture process runs at higher volumes on standardised systems from larger factories.
Factory finishing (powder coating), hardware, and double glazed sealed units cost similar amounts for both materials. The difference sits in labour time per frame, which is consistently higher with steel.
Transport, handling, and on-site installation can also be cheaper for aluminium. Aluminium windows are lightweight and require less structural support, making them easier to manoeuvre on upper floors and tight urban sites. Steel frames are heavier, bulkier, and may need additional personnel or mechanical assistance on the day of professional fitting.
Appearance: Aluminium vs Steel Windows in Heritage and Art Deco Settings
Many homeowners want the Crittall look as closely as possible, so aesthetics rank alongside cost in the decision.
Steel windows offer distinctive slim sightlines for a unique aesthetic. Profile widths on a genuine steel window can be as narrow as 20–25 mm. Modern aluminium steel look windows replicate this with sightlines around 25–35 mm, close enough that the difference is difficult to spot from the pavement. Steel is roughly three times stronger than aluminium in its raw form, which is the structural reason steel can achieve thinner bars.
Aluminium steel look windows replicate the feel of old steel and Crittall windows through:
- Horizontal and vertical grid patterns matching Georgian style or Art Deco layouts
- Deep bottom rails
- Heritage-style handles, stays, and other hardware
- Optional astragal bars echoing original pane layouts and unique style
Internal steel screens for partitions and doors retain a visual sharpness that is hard to replicate exactly, but aluminium offers a close, more economical interpretation.
Colour options influence apparent authenticity. Black and anthracite are the classic steel look for Crittall-style designs. Off-white and softer tones suit Arts & Crafts or Edwardian era homes. Both steel frames and aluminium frames can be finished in virtually any RAL colour. Aluminium powder coating lines often carry more stock shades and shorter turnaround times, giving you a full range of colour options when specifying for period homes.
Performance and Thermal Efficiency: Double-Glazed Steel and Aluminium Windows
Both high-quality aluminium and steel windows can now meet or exceed Part L energy requirements in England. Current building regulations require replacement window U-values of 1.4 W/m²K or better, or compliance via Window Energy Rating band B.
Thermal breaks are the key. In aluminium heritage systems, polyamide strips separate the inner and outer frame faces. In steel systems like the Crittall T60, a similar thermal barrier is engineered into a slimmer profile. Without a thermal break, old steel windows sit at 4–6 W/m²K; with one, both materials reach 1.4–1.6 W/m²K with double glazing.
Modern steel windows can achieve a U-value as low as 1.4 W/m²K. Aluminium is widely available and offers good thermal efficiency at the same level, with the option of triple glazing pushing U-values to approximately 1.0–1.2 W/m²K for projects that demand higher performance, such as properties on busy streets needing acoustic glass or south-facing elevations requiring solar control.
For most period homes, the difference in annual running costs between well-specified steel and aluminium is smaller than the difference in upfront cost. Aluminium windows typically cost less than steel windows and still deliver equivalent thermal performance, which is why aluminium windows offer greater budget-to-performance value for most renovations.
Steel windows also offer excellent fire resistance and security features, which can matter in commercial conversions and multi-occupancy buildings.
Durability, Maintenance and Lifespan
Both aluminium and steel have excellent durability if properly maintained, but they age differently.
Steel windows:
- Structural strength is outstanding. Steel windows can last over 60 years with proper maintenance; many original metal windows from the 1930s are still in use after 90 years.
- Steel's main vulnerability is rust due to moisture and salt exposure. Regular cyclical treatments (repainting every 5–8 years, checking putty, clearing drainage channels) are non-negotiable.
- Coastal exposure requires high-quality finishes for both aluminium and steel. Marine-grade specifications for steel frames are crucial to avoid premature failure. Plymouth's coastal climate, for example, impacts window frame longevity and performance and demands especially rigorous protective coatings.
Aluminium windows:
- Aluminium naturally resists corrosion when finished with marine-grade powder coating. High-quality aluminium frames generally withstand coastal weather with minimal degradation, making choosing aluminium a hassle-free, highly durable solution for coastal locations.
- Routine maintenance is limited to cleaning and occasional hardware lubrication. Aluminium requires low maintenance compared to steel, which requires cyclical treatments for rust. Aluminium generally has lower lifecycle upkeep costs than steel.
- Expected lifespan is 30–40+ years, with recyclability at end of life reducing environmental impact.
Environment matters. Urban pollution, maritime exposure, and industrial settings all increase the maintenance burden on old steel. Repairing existing steel windows may be more sustainable in some cases, while heavily corroded old frames are often more cost-effective to replace with new aluminium windows.
Planning, Listed Buildings and Conservation Areas
In the UK, planning and heritage status can override personal preference or budget when choosing window materials.
Listed buildings: Listed Building Consent is typically required to change existing windows on a listed façade. Conservation officers may insist on like-for-like steel replacements, traditional glazing bar patterns, and specific glass types. Authentic steel windows may be required in conservation areas, affecting both design and cost. In these cases, only steel will satisfy the planning requirement.
Conservation areas: Aluminium heritage windows are often acceptable where they closely replicate existing steel windows in sightline width, casement windows layout, and glazing bar pattern. The key is careful detailing and slim profiles that are indistinguishable from original steel at street level.
Examples:
- Replacing original 1930s Crittall windows on a locally listed Art Deco block will almost certainly require a genuine steel window or thermally broken steel system.
- Upgrading old steel in an interwar suburban conservation area with aluminium windows that match original sightlines is increasingly accepted by local authorities.
Consult your local planning department early. Submit drawings, section details, and sample frames when proposing aluminium as an excellent alternative to steel. Compare aluminium options against the existing windows on your façade before formal application.
Replacing Existing Steel Windows: Repair vs Aluminium or New Steel
Many projects involve existing steel windows that are rusty, single glazed, or draughty, but not always beyond repair.
When repair makes sense:
- Frames are largely sound with localised corrosion only
- The building has high heritage significance requiring retention
- Budget favours staged refurbishment over full window replacement
When replacement is better value:
- Extensive corrosion or frame distortion
- Poor thermal performance, condensation, and security problems
- Occupants need improved performance and ease of use
Three paths compared:
| Path | Typical cost (per window) | Best for |
|---|---|---|
| Repair and refurbish existing steel | £500–£900 | Heritage retention, limited budget |
| Replace with new genuine steel | £1,400–£2,800 | Maximum authenticity, listed buildings |
| Replace with heritage aluminium | £1,000–£2,000 | Cost, speed, low maintenance |
Aluminium windows can often be installed into original stone or brick openings, and in some projects into existing timber subframes, minimising disruption and cost. Steel windows can be installed directly into stone or timber subframes too, but steel requires precise measurements for accurate installation, and older properties may have irregular window openings affecting installation.
Design Choices: Casement Types, Glazing and Colour Options
Both aluminium and steel windows give wide design flexibility. Aluminium usually offers the larger catalogue and more cost-effective customisation.
Casement and window styles for period properties:
- Side-hung casement windows for a traditional steel look
- Top-hung vents for discreet background ventilation that lets natural light in without compromising security
- Fixed lights to replicate tall, slender stairwell or landing windows
- Aluminium can mimic traditional sash window designs, including Edwardian sash windows, with horizontal glazing bars
Glass options for both aluminium and steel include safety and laminated glass for doors and low-level glazing, acoustic glass for city properties near busy roads, and obscure or textured patterns echoing 1930s styles. Both materials allow for custom glazing styles and hardware options.
Colour: Black and dark grey remain the classic choices. Steel frames can be finished in virtually any RAL colour; aluminium frames can be powder-coated in an extensive range of finishes. Aluminium powder coating lines often offer shorter lead times and more stock shades, so you can create a bespoke appearance in virtually any RAL colour without long waits.
Project Timelines, Lead Times and Site Considerations
Beyond price, lead time can be decisive when choosing between aluminium and steel for renovations, extensions, or new builds.
Aluminium heritage windows from mainstream suppliers carry lead times of 3–4 weeks for standard colours and 4–5 weeks for bespoke RAL. Steel windows, especially thermally broken or bespoke models, often require 3–5 months. Aluminium windows typically have shorter lead times than steel windows across the board.
Site logistics: Aluminium's lighter weight makes handling easier for upper floors and tight urban sites. Steel frames may require more manpower or mechanical lifting, increasing installation cost. Installation tolerances are crucial for fitting steel windows accurately on older buildings with non-standard openings.
For project sequencing, the speed of aluminium manufacture helps keep building projects on track when deadlines are tight, particularly when façade works, roofing, and internal finishes all depend on windows being installed on schedule.
Early technical input from your window supplier helps coordinate structural openings, cavity closers, and internal reveals, avoiding costly changes on site whether you are specifying steel or aluminium.
How to Decide: Choosing Between Steel and Aluminium for Your Period Property
The right choice depends on budget, planning constraints, architectural significance, and how long you plan to keep the property. Choosing between steel and aluminium windows involves balancing upfront investment and ongoing upkeep.
A simple framework:
- Choose genuine steel where authenticity, prestige, and ultra-slim lines are the top priority, budget allows, and planning demands it.
- Choose heritage aluminium where cost, speed, and low maintenance matter most, especially for whole-house upgrades or larger portfolios. Choosing aluminium provides a practical, high-performance solution for the majority of period property renovations.
If you are working on listed buildings or in strict conservation areas, prioritise planning compliance and expert advice before committing to a material. Trade professionals (architects, developers, registered installers) should obtain comparative quotes and section details for both materials on their specific project rather than relying on generic price guides.
Request a trade quote for bespoke heritage aluminium windows to get detailed, no-obligation pricing and to discuss where aluminium is a suitable replacement for steel on your current schemes.
FAQs: Steel vs Aluminium Windows Cost and Heritage Projects
Is there a typical percentage saving when choosing aluminium windows instead of steel?
On comparable heritage-spec openings (thermally broken, double glazed, narrow sightlines), aluminium heritage windows cost about 30–50% less than new genuine steel. The exact saving depends on window size, configurations, and the steel system specified. On a whole-house project, the cumulative difference can run into thousands of pounds.
Can I mix steel doors with aluminium windows on the same elevation?
Yes. Some projects use genuine steel for a prominent entrance door or internal screen and aluminium for the remaining windows and doors. Matching the RAL colour and glazing bar proportions across both materials keeps the elevation consistent. Discuss this with your supplier early so that section profiles align at junctions.
Do heritage aluminium windows qualify for any grants or VAT reductions on renovation projects?
Window replacement on listed buildings may qualify for reduced or zero-rate VAT under certain conditions (approved alterations to listed buildings). Specific grant schemes vary by local authority and change year to year. Check with your local conservation officer and HMRC guidance for the current position on your project.
Will aluminium windows be accepted in every conservation area as a replacement for old steel?
Not automatically. Each local planning authority sets its own standards. Many conservation areas now accept aluminium heritage systems where the appearance, sightlines, and glazing bar details closely replicate the original. Others still insist on steel. Submit sample sections and elevation drawings with your application to improve your chances.
How early in my project should I get a quote for heritage aluminium vs steel windows?
As early as possible, ideally at design stage or before submitting a planning application. Early quotes let you compare aluminium and steel costs accurately, confirm lead times, and coordinate with your builder's programme. For steel, allow at least 3–5 months from order to delivery; for aluminium, 3–5 weeks is more typical for standard colours.