Period properties in and around Borehamwood — Victorian and Edwardian terraces, 1930s semis, converted schools and studios — often lose their character when their original steel windows are replaced with generic modern frames. In the last decade, heritage-styled aluminium systems have become good enough to be a serious alternative: they replicate the slim sightlines of original steel joinery while meeting current thermal and safety standards. This article covers where the category has got to and how to specify it well.
What "heritage aluminium" actually means
Heritage aluminium is a category of window and door systems specifically engineered to look like traditional steel-frame windows — the fine-grid Crittall-style joinery of the 1920s-1950s. The frames are thermally broken aluminium, but the visible profiles are much slimmer than standard modern aluminium systems, achieved through squared-off external shapes and reduced sightlines. Internal glazing bars replicate the grid pattern of the original.
Where it works well
- Period residential: replacing failed original steel or timber Crittall-style windows in Victorian, Edwardian and inter-war housing.
- Converted industrial or civic buildings: old schools, warehouses, chapels — where large multi-pane windows were the original feature.
- Contemporary internal features: internal glazed screens and doors within open-plan renovations, where the industrial look is chosen for aesthetic reasons.
Where it does not work
Heritage aluminium is not a universal substitute for original steel in every context. On listed buildings, planners typically require like-for-like replacement in steel — heritage aluminium is not acceptable. On some conservation-area properties, heritage aluminium is permitted only with specific glazing bar profiles and colours. Confirm with the local planning authority before specifying, particularly around Elstree, Barnet Vale and other conservation-designated pockets.
Choosing a system
Several systems houses now produce heritage-styled aluminium. The main considerations across the market:
- Sightlines: the good heritage systems achieve visible sightlines of 55-70 mm on the frame — genuinely close to original steel.
- Glazing bar profile: flat, T-section or butt-jointed. Butt-jointed with structurally-glued bars gives the most authentic look.
- Colour: black is the default, but graphite grey, dark bronze and RAL 9005 matt work well. Anthracite (RAL 7016) is usually too grey.
- Corners: traditional steel used solid corner sections. Heritage aluminium can now achieve the same with mitred welded corners on the best systems.
System houses including Kobbe's heritage-styled ranges and specialised UK ranges offer the sightlines and finishes appropriate to period work. Schüco's own residential systems can be specified in heritage guise for internal screens.
Thermal performance
This is where heritage aluminium beats original steel decisively. Original steel Crittall-style windows had negligible thermal performance — single glazed, no thermal break, direct cold bridge from outside to inside. Heritage aluminium at current spec is thermally broken and double or triple glazed, hitting whole-window U-values in the 1.4-1.6 range for retrofit and lower for new-build. On a period house, moving to heritage aluminium can meaningfully reduce heating cost while preserving the aesthetic.
Doors, not just windows
Heritage aluminium also covers doors — French doors, sliding doors and even bifold sets designed to read as traditional steel joinery. The visual impact of a heritage-styled bifold on a period rear extension is one of the strongest current design details in UK residential work. If you are looking at heritage aluminium for the rear of a Borehamwood or Hertford property, the door and window package usually reads best when they share the same profile family.
Installer selection
Not every aluminium fabricator does heritage work well. The sightlines are unforgiving of small errors — an out-of-square opening or a slightly bowed head shows up more obviously than on chunkier modern profiles. Look for installers who can show you completed heritage work at addresses you can visit. 5EC lists heritage aluminium windows and doors as a specific specialism, which is worth knowing if you are considering the option locally.
Practical checks
- Insist on a site sample or a showroom visit before ordering — heritage details vary meaningfully between systems.
- Confirm the internal glazing bar is structural, not stuck-on.
- Ask about handles — heritage-appropriate handles matter for the finished look.
- Check the frame corner detail — mitred and welded reads best.
Cost expectations
Heritage aluminium sits at a premium to standard aluminium — expect 15-30% more per opening for the specialised profiles. Compared to genuine restored or new steel windows, though, it is significantly cheaper — and comes with a modern warranty and modern thermal performance. For most homeowners with a period property outside listed constraints, this is the sensible landing point.
The category has genuinely improved. A heritage aluminium installation done well in 2025 or 2026 is nearly indistinguishable from restored original steel from a couple of metres away — and outperforms it comprehensively on every measurable spec. For period properties around Borehamwood where planning permits, it deserves serious consideration.