Heritage Aluminium Windows: The Steel Look Without the Steel

Heritage aluminium windows are slim, thermally broken aluminium frames designed to look like the old steel windows found in 1920s to 1950s houses, warehouses and period conservatories. They keep the fine sightlines and horizontal glazing bars of steel, but they do not rust, they take modern double or triple glazing, and their frames carry a thermal break that original steel never had. They are the window most planning officers are happiest to see on a conservation-area renovation.

What is a heritage aluminium window?

The name covers two things. The first is a steel-look frame: a slim aluminium profile, usually powder coated in black or a dark grey, with applied or integral glazing bars that divide the pane into the small rectangles that steel windows were known for. The second is a heritage proportion: tall narrow lights, a horizontal top light, and a frame that sits close to the face of the wall the way old metal windows did.

Are heritage aluminium windows the same as Crittall windows?

No. Crittall is a manufacturer of steel windows, and the name is used loosely for the whole style of slim black frames with glazing bars. "Crittall style" aluminium windows copy that look in thermally broken aluminium: they are not steel and not made by Crittall. The practical differences are the ones below: aluminium runs warmer, will not rust and needs no repainting, while real steel can achieve a slightly finer sightline and is the authentic material on a listed building.

Why choose a steel look in aluminium rather than real steel?

Real steel windows are still made, and on the right building they are beautiful. The difficulty is thermal. Steel conducts heat, so an original steel frame runs cold, collects condensation and, without a thermal break, cannot meet current Building Regulations for a replacement window without special treatment. Repairs are also specialist work.

Aluminium solves the physics. A thermally broken aluminium frame has an insulating barrier between the outside and inside faces of the profile, so the inner surface stays close to room temperature. The frame will not rust, the powder coat does not need repainting, and the section can be made almost as slim as steel. The steel-look option on our aluminium windows and doors is made to measure in the same thermally broken specification.

How slim are the sightlines?

The sightline is the visible width of frame plus glazing bead when the window is closed. Original steel windows were remarkably slim, often under 30mm. A good steel-look aluminium system gets close to that, which is the whole point of the profile; a standard aluminium casement is wider, and an off-the-shelf frame wider still. If a supplier cannot tell you the sightline in millimetres, ask another supplier.

Glazing bars matter as much as the frame. Applied bars on both faces of one unit, with a spacer inside, read convincingly from a few metres; bars only between the panes are cheaper and look flat; true divided lights are the most authentic and the most expensive. On a listed building the conservation officer may specify which.

Which homes suit heritage aluminium windows?

Interwar houses with original metal windows are the obvious candidates, and so are warehouse and mill conversions. They also work on Victorian and Edwardian homes where the original timber sashes are beyond repair and the owner wants a more industrial look (paired with restored or new Victorian front doors), and they are a natural partner to a glazed link or a glass extension where the new glazing should quietly echo the old.

On a modern house they are a style choice rather than a conservation one. Black steel-look frames on a rendered or brick contemporary home give a crisp, drawn-line elevation, and the same frames can carry through to the doors. Our aluminium casement windows post covers the plainer modern profile if that is the better fit.

What about planning and conservation areas?

In England, replacement windows on a house, including one in a conservation area, are usually permitted development if they are similar in appearance to the existing ones. An Article 4 direction can remove that right, and a listed building always needs listed building consent. Steel-look aluminium is often accepted in place of original steel, but it is not automatic.

Building Regulations apply to every replacement window: the energy standard, safety glass in doors and low-level glazing, and escape windows where required. A thermally broken frame with modern double glazing meets the energy standard comfortably; single-glazed steel does not.

How does the performance compare to a modern aluminium window?

Thermally, a steel-look frame is a modern aluminium window with a different face: the same thermal break, glazing options and multi-point locking. The difference is glass area. More frame and bar per square metre lets in slightly less light, so on a south-facing room keep the bars to the top light. Whether a given profile takes triple glazing depends on the system and the sightline you want to keep.

What do heritage aluminium windows cost?

A steel-look aluminium window costs more than a plain aluminium casement of the same size, because of the extra profile work and the glazing bars, and considerably more than a standard off-the-shelf frame. Size, number of bars, glazing and opening arrangement set the figure, so we price window by window. Our guide to aluminium windows cost explains what drives the price.

Heritage aluminium windows questions, answered

Can I have the steel look in a colour other than black?

Yes. Black and dark greys are the traditional choices because original steel was painted dark, but the frames are powder coated and any RAL colour is available, including a different colour inside and out.

Will the glazing bars trap dirt?

Applied bars are bonded flush to the glass with no ledge, so they wipe clean with the pane. Self-cleaning glass helps further on the outside.

Do they need maintenance?

No repainting. Wash with mild detergent once or twice a year and lubricate the hinges occasionally.

Talk to our design team

If your house has, or once had, steel windows, this is the way to keep the look and lose the cold. We are happy to talk through the elevation with you and show samples of the sections side by side.