Steel Windows & Doors

Everything you need to know

Table of Contents

    1. Why Steel?
    2. Types of Steel Windows & Doors
    3. Metal Windows: Steel or Aluminum?
    4. Glass Options
    5. Glazing Beads
    6. Cost
    7. Finishes
    8. Who Manufactures Steel Windows & Doors?

Why Steel?

    • Strength – Steel is stronger than aluminum, wood, or vinyl for making window and door frames and sashes.  In fact, vinyl extrusions use steel inside of them to make them stronger.
    • Durability – Steel is tougher and more resistant to physical attack than any other material.  At universities across America, 60-year-old steel windows only need some glass replaced and a new paint job to last another 60 years.  It is no accident that cars, bridges, and skyscrapers are made out of steel.
    • Thinness – No material can be used in as small a cross section than steel.  This supports the aesthetic required in modern architecture.

Types of Steel Windows & Doors

Steel window and door profiles are created by two different methods:

    • Hot-rolled steel – In order to form the steel its temperature is raised to red-hot.  This makes it easier to form into the exact shape that is desired.
      • Hot-rolled Bars – are one of the oldest methods of making steel windows.  This technology started out in England in the early 1800’s with the growth of the railroad and coal industries.  This method allows for intricate profiles to be formed in mostly “L”, “T”, and “Z” shapes that allow for every possible combination of fixed, inward or outward operating windows with glazing beads on either the inside or outside.
      • Hot-rolled Sheets – are made flat in huge coils with the same, but less intricate method.  These sheets are then usually cut with lasers or waterjets into required layouts complete with fabrication holes and slots.  The cutout sheets can then be pressed into 3-dimensional shapes.  This modern use of hot-rolled steel allows for software-driven solutions that are more accurate and can be fabricated faster than the bar method.  This happens without any compromise to the strength and durability of ALL hot-rolled steel.
    • Cold-rolled Steel – comes late to the party as a method for simulating hot-rolled steel profiles.  In this case very thin steel sheets are bent using continuous rolling dies (like making rain gutters) to create”L”, “T”, and “Z” shapes that are hollow.  This method is much less expensive, and doesn’t give the same solid strength and feel of Hot-rolled steel.

Metal Windows: Steel or Aluminum?

Steel windows and doors are usually put into the greater category of metal windows where the “other” metal is aluminum.  A fair measure between the two materials would compare them in strength and thermal performance.


Steel as a material is three times at resisting windload deflection than aluminum and 35% stronger in tensile strength.  Not only is the material alone stronger, but the way it is made into frames is stronger.  Steel frames are welded which is as strong or stronger than the material actually making a 90-degree turn while aluminum is mechanically connected at corners with either screws or crimps which loosen over time allowing sagging.

Thermal Insulation

Even without the benefit of a thermal break, steel is four times better than aluminum.  When aluminum was introduced as an alternative to steel windows in the 1960’s they proved to be a disaster in cold climates because of condensation.  The aluminum manufacturers had to invent thermal breaks.

Steel windows continued to compete with thermally broken aluminum until about 10 years ago when thermal breaks were introduced into cold-rolled steel sections.  Hot-rolled steel windows developed new technology more recently and now compete with better thermal insulation values to thermally broken aluminum windows and doors.

Glass Options

The world is your oyster when it comes to glass options.  Any kind of single or insulated glass can be included in steel windows and doors.

Single Glass

Single glass is not thermally or acoustically insulated, but it still keeps out rain and wind.  In some climates is acceptable, but modern building codes often preclude it on exterior openings.

To help with acoustic insulation, laminated glass can be the “single” glass option alternative to monolithic single glass.

Insulated Glass

List of options available for the IG package on either or both glass panes of double paned or all three of triple panedglass:

    • double paned
    • triple paned
    • low-E glass
    • tinted glass
    • reflective glass
    • laminated glass (helps with UV and sound insulation also)
    • warm edge spacer like Super Spacer®
    • gas-filled “air” space with argon or krypton

These options need to be chosen with the help of an expert to select the perfect combination to accomplish your design goal for your building in your environment.

Factory vs. Field Glazing

Most steel windows and doors are shipped from the factory WITHOUT glass in them.  This is mostly because the installation screws are located within the frame under the glass.  Most window and door installers are NOT glaziers and very often make a perfectly fine steel window work poorly because of improper glass installation.

There are a few premier manufacturers who ship factory glazed steel windows and doors.  This is always preferable so that the glass is properly mounted and blocked for sag-free, long life.


Glazing Beads

Glazing beads or stops as they are sometimes called are the removable strips that allow the glass to be held in place and also be removed if the glass needs to be replaced.  

In steel windows, the glazing bead is most often made from extruded aluminum to reduce cost, allow a better fit, and offer more different shapes.

Some manufacturers offer bent steel beads with screws to hold them on either concealed or exposed.

Accoya® is a Clever Alternative

At least one clever devil is using Accoya® glazing frames to dramatically improve thermal performance and aesthetic appeal over all of the alternatives.

It is always best to have the removable glazing beads removable from the inside rendering the exterior steel-to-glass joint uncompromised.  The removability, if on the outside, makes for a water entry point that promotes both leaking and rusting.


Vinyl windows are the least expensive windows and doors available, and in my opinion, they look like they are also.  In double hung varieties and small casements, they look ok and they perform very well thermally.  However, plastic is plastic.

Wood windows are a little bit more expensive than vinyl.  Wood windows with vinyl or aluminum are even more expensive, but since wood doesn’t weather very well are worth the additional cost in reduced maintenance.

Metal Windows Cost More Than Plastic or Wood Ones

Aluminum windows are more expensive yet with thermally broken windows representing most of that market share.  Aluminum windows are not so often used residentially, but they dominate the commercial and high-rise market.

Steel windows are at the top of the cost structure of the window and door industry with the exception of exotics like bronze, German silver and gold (if such a thing exists).  Again thermally broken or improved steel windows are even more expensive.


In the early days of steel windows and doors, they were shipped unfinished.  Then primers like “tinners red” were applied to untreated steel prior to shipping.  Those days are long gone.


The most important part of steel window finishing is pretreatment.  There are many pretreatment options and there is a wide difference in the results.  

Cleaning the steel frames is either not done as in the case of galvanizing which counts zinc coating sticking to the steel.  This naked treatment is a problem because when knocked it can cause the entire painted area to fall off.  Hot-dipped glavanizing also drips creating  thick areas

Phosphate is the most popular and used by powdercoat finishers almost exclusively.  It is a cleaning and etching process but has no mechanical component.  Zinc-rich epoxy is then usually applied to resist rusting

White sandblasting and 83% zinc dry film primers like Tnemec Series 94 is the gold standard.

Top Coat

Most popular is powder coating for the finish coat.  Polyester dust is melted onto the surface over the primer and it is available in lots of colors.  The main advantage of powder is that it is extremely friendly to the environment.  The downside is that it is not so easily repaired or touched-up.

Wet paints are the other finish of choice and mainly are 2-part aliphatic urethanes that are durable and often used to paint airplanes and other large objects that don’t easily fit into ovens.

Powder and wet paints also are available in flourocarbon compounds that are superior at resisting the fading effects of the sun.

Who Manufactures Steel Windows & Doors?

Made with Hot-rolled Bar

Hot-rolled bars are made in Switzerland and England is the largest steel window market nearby.  Leading manufacturers in Europe that also sell in the U.S. are:

    • Crittall
    • Clement

U.S. Hot-rolled bar window fabricators are lead by:

    • Hope’s
    • Optimum
    • A&S
    • Bliss-Noram (actually produced in Canada)
    • Torrence

Made with Hot-rolled Sheets

    • Arcadia (Thermal Steel)
    • 2Fold® Doors

Made with Cold-rolled Bent Shapes

    • Dynamic Arte’ (Canadian)
    • Brombal

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