Custom steel, bronze and stainless windows — including fire-rated systems
Optimum Window Manufacturing is a family-owned business at 28 Canal Street in Ellenville, upstate New York. Founded in 1985 by Candido Perez, it has grown into the largest and most diversified manufacturer of fire-rated and architectural steel windows in the United States, and everything it makes is custom — there is no catalogue of standard sizes.
We supply and install Optimum systems across New York City, New Jersey and Pennsylvania. Being a few hours up the Thruway rather than across an ocean makes a practical difference on custom work: shop drawing revisions move faster, and a site issue can be resolved by people who can drive down.
Steel solves two problems no other material solves as well. It is strong enough to carry large glass on very slim profiles, and it can be fire-rated. Below is when each of those actually matters, what the material range covers, and what to expect from a custom steel order. Full technical documentation is on Optimum's website, which opens in a separate window.
Steel has a far higher strength-to-section ratio than aluminium, wood or vinyl. For a given span and a given weight of glass, a steel frame can be dramatically thinner while carrying the same load.
That is the whole aesthetic argument. Profiles can come down to dimensions no other material reaches, producing the near-frameless look that modern architecture wants and that historic steel windows had by default. Where the brief is maximum glass and minimum frame, steel is the material that gets there.
Rigidity has a second consequence that shows up over decades rather than immediately. Steel does not warp or twist with moisture the way wood can, does not become brittle like vinyl, and resists racking — losing squareness — far better than aluminium. A large casement or a monumental pivot door that would gradually go out of true in a softer material stays aligned in steel. That is why operation on a well-made steel window still feels precise after decades.
The trade-off is weight and cost. Steel units are heavy, which affects structural support, hardware selection and installation method. They are not a default choice; they are the right choice for specific problems.
Most of this page describes reasons to prefer steel. Two conditions make it a requirement.
Fire-rated openings. Where code demands a rated opening — at a lot line, in a stair or corridor enclosure, between certain occupancies — an ordinary window will not comply, whatever its quality. Fire-rated assemblies are a specialist product, and Optimum's core business is exactly this. The FR8600 series, for example, is a UL classified and labelled 45-minute fire-rated projected window with a self-closing mechanism.
Note that the rating belongs to the tested assembly — glass, frame, hardware and closing mechanism together — not to the glass alone. Substituting any component outside the listing voids it. See our SAFTI FIRST page for the fire protective versus fire resistive distinction, which governs which product a given opening actually needs.
Landmark and historic restoration. Where a preservation commission requires replacement windows to match the original profile, and the original was steel, no clad or aluminium unit will be approved. The sightlines simply cannot be reproduced. In New York, with its extensive landmark designations, this comes up constantly.
In both cases the specification is driven by compliance rather than preference, and it is worth establishing early because it changes both the budget and the programme.
Steel's historic weakness was thermal conductivity. Traditional steel windows were cold in winter, prone to condensation, and would not meet any modern energy code.
Thermally broken construction addresses this by physically separating the interior and exterior steel profiles with a non-conductive barrier, so there is no continuous metal path from outside to inside. Optimum's thermally broken series — including RTS-430, RTS-430+ and 6500SB — are built this way.
Paired with modern glazing — insulated units with Low-E coatings and argon fill — thermally broken steel meets current energy requirements while keeping the slim profiles that made steel worth specifying in the first place.
This is the development that made steel viable again for occupied buildings in cold climates. Anyone whose impression of steel windows comes from a draughty pre-war loft is working from outdated information.
Optimum is unusual in running divisions across several metals, which matters when a project needs more than one.
| Material | Why You Would Choose It | Typical Application |
|---|---|---|
| Steel fire-rated and non-rated | Maximum strength, slimmest sightlines, fire ratings available | Landmark restoration, rated openings, monumental glazing |
| Bronze alloy | Develops a living patina; traditional luxury appearance | High-end residential, institutional and civic entrances |
| Stainless steel | Corrosion resistance in coastal or aggressive environments | Waterfront property, harsh exposure, contemporary work |
| Aluminium | Lower cost where steel's strength is not required | Non-rated openings on the same project, for consistency |
The practical benefit is consistency of detailing. On a building where the street elevation calls for bronze, a coastal elevation needs stainless, and the rated openings must be steel, having all of it from one manufacturer means the profiles, finishes and hardware relate to each other rather than being three separate procurement exercises that do not quite match.
Because everything is custom-engineered, the operation range is broad: casement, awning and projected windows, fixed and combination units, horizontal sliding, pivot doors, bi-folding systems and lift-and-slide doors.
Casements use multipoint locking hardware, which draws the sash into the frame on all sides for a compression seal — the same principle described on our casement windows page, and one of the reasons casements outperform sliding operations on air infiltration.
Fire-rated units carry additional hardware requirements. Self-closing mechanisms, specific hinge types and listed fasteners are part of the tested assembly rather than optional extras, which is why a rated unit cannot simply be specified as its non-rated equivalent with a label attached.
Steel must be finished properly or it will corrode, and the finishing programme is as important as the frame.
Factory-applied powder coating is the standard, oven-cured to a hard finish that resists chipping, scratching and UV degradation, available across a wide colour range. Matte blacks and dark bronzes dominate contemporary specifications.
Galvanising before painting gives maximum corrosion protection and is worth specifying for exposed or coastal work, where a paint film alone is doing all the work.
Specialty finishes can reproduce the appearance of blackened steel or oil-rubbed bronze while retaining a modern protective topcoat — the look of a living finish without the maintenance a genuinely uncoated one demands.
For bronze, the patina develops naturally over time and is generally the point rather than a problem, though it can be controlled or arrested depending on the appearance wanted. Establish this at specification stage, because expectations about how bronze will look in five years vary widely.
On restoration work the muntin profile is frequently the detail an approval turns on.
Steel allows intersecting muntin profiles far slimmer than other materials, which is exactly why original steel windows look the way they do and why substitutes rarely convince. Traditional putty-glazed profiles can be reproduced closely.
For insulated glazing, simulated divided light uses bars applied to the interior and exterior with an aligned spacer inside the sealed unit, giving genuine shadow lines while retaining the thermal performance of a double-glazed unit. That combination — historic appearance, modern performance — is what makes landmark-compliant replacement possible at all.
If you are matching existing windows, photographs and a measured muntin section are the most useful things you can send us.
Optimum uses 100% recycled steel and runs a closed-loop process, with scrap generated in fabrication returned into production.
Steel is also fully recyclable at end of life, unlike composite assemblies such as vinyl-clad wood where the materials cannot practically be separated.
The larger environmental argument is longevity. A properly finished and maintained steel window is a very long-life product. A window that is not replaced every twenty-five years consumes no raw material for its replacement and generates no waste stream, which outweighs most differences in embodied carbon at manufacture.
This is not a product you order in a hurry, and being realistic about that from the start prevents difficulty later.
Every unit is made to shop drawings. The sequence runs design consultation, then approved CAD shop drawings, then fabrication, then delivery and installation. Each stage takes time, and on landmark projects the approvals stage frequently takes longer than the manufacturing.
Our advice is to start the conversation before the drawings are finalised. We can advise on achievable spans, hardware behaviour, thermal performance and whether a detail as drawn will work, at a point where changing it costs nothing.
Installation matters more here than on ordinary glazing. Steel units are heavy and dimensionally precise. They need correct structural support, accurate setting, and perimeter detailing that ties the frame into the wall's air and water barrier — sill pan flashing with end dams, clear weep paths, properly tooled sealant joints. A precisely made steel window set into a poorly detailed opening will still leak, and that failure is not a manufacturing defect.
Send us the openings, the required ratings if any, whether landmark approval is involved, and photographs of anything being matched. We will tell you what is achievable and what the realistic programme looks like.
SAFTI FIRST Commercial Aluminum Casement Windows Fixed Windows Laminated Glass Curtain Wall Systems
Tell us about the opening and we will specify it for you.
