Steel-Framed Windows Leap Forward Into Modern Designs
With a mild-mannered profile but super strength, steel-framed windows are champions of design freedom
Houzz Contributor. My name is Bud Dietrich and I am an architect located in the Tampa Bay area of Florida. I am licensed to practice architecture in Illinois, Florida, New Jersey & Wisconsin and I am a certificate holder from the National Council of Architectural Registration Boards (NCARB). Since 1996 I have worked from my home office and provide full architectural services exclusively to the single family residential market. My passion is to transform my clients' houses into their homes. I strive to have the "new" home accommodate my clients' lives without fighting them at every junction. I look to add curb appeal to encourage a beautiful streetscape. And I design any addition to look and feel like it has always been there.
Our projects have won numerous design awards as well as having...
Houzz Contributor. My name is Bud Dietrich and I am an architect located... More »
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The Industrial Revolution gave us many new materials and technologies, from the elevator to the concept of a curtain wall construction. Not the least of these was the introduction of sheets of glass set in metal frames.
Introduced on a large scale at the Crystal Palace, which housed the Great Exhibition in 1851, sheets of plate glass held in place by a metal framework quickly found their way into architectural design. Then, with lighter and stronger steel replacing cast iron, windows manufactured by the likes of Henry Hope & Sons found their way into residences. By the 1930s, architects like Frank Lloyd Wright popularized steel-framed windows.
However, starting in the 1960s these windows became less and less popular. Contributing to their demise was the lack of thermal efficiency of the original windows. Made of a single sheet of glass and a thin steel frame, these windows were great conductors of cold from outside to inside.
But that's all changed. With better materials, designs and finishes, these windows are undergoing a resurgence.
Introduced on a large scale at the Crystal Palace, which housed the Great Exhibition in 1851, sheets of plate glass held in place by a metal framework quickly found their way into architectural design. Then, with lighter and stronger steel replacing cast iron, windows manufactured by the likes of Henry Hope & Sons found their way into residences. By the 1930s, architects like Frank Lloyd Wright popularized steel-framed windows.
However, starting in the 1960s these windows became less and less popular. Contributing to their demise was the lack of thermal efficiency of the original windows. Made of a single sheet of glass and a thin steel frame, these windows were great conductors of cold from outside to inside.
But that's all changed. With better materials, designs and finishes, these windows are undergoing a resurgence.
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by Fallingwater
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| Perhaps Frank Lloyd Wright's most celebrated design, Fallingwater owes much of its visual success to the design freedom given by the steel-framed windows. |
Since the 1930s improvements made to the metal framework's finishes have given new life to these window systems. Virtually unlimited color choices enable designers to create inspired window walls.
A hallmark of these glazing systems is the minimal amount of framing material needed for structural integrity. Wood frames for glass doors must be considerably larger, adding a lot of visual weight to the door. Steel frames can be very light and thin due to the strength of the material.
The thinness of these steel frames allows them to become mere two-dimensional grids, almost painterly in effect. The view out becomes flattened, not unlike some modern paintings, such as those of Mondrian.
Rather than a large beam or header supporting the door, all that's needed is a pencil line of steel.
Like in some of the great 19th- and early-20th-century factories, warehouses and other industrial buildings, these steel-framed glazing systems can impart an industrial aesthetic when employed from floor to ceiling and corner to corner.
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| While these systems have their roots in the industrial age and really do have that industrial aesthetic, they can be used with a traditional-style home. In fact, like a yin and yang approach, these steel-framed glazing systems can enrich a traditional interior. |
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| These systems are naturally suited to open corners, where sheets of glass are formed to create open corner windows. Thin lines of steel provide a minimal amount of framework, creating just a mere screen between inside and out. |
Ideabook published on Nov. 26, 2012.
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Don't know about the thermal performance when the frames are very thin overall - there's very little 'room' for the insulation, no?
But then again there is a Swiss company called Sky-Frame, see sky-frame.ch/e/. They build windows with almost invisible metal frames, yet the U-values are incredibly good. So it IS possible, albeit prohibitively expensive. 70 feet of floor-to-ceiling windows would have cost us 80,000 Euros, that is over $100k ...
@midmodfan - Unfortunately, these systems aren't inexpensive. Last time we priced out using Hopes Windows it was considerably more than standard windows but way less that what you mention.
What one has to take into consideration with steel is that it only transfers around 1/3rd of the heat energy as say aluminum and so the aluminium window manufacturers have a much harder time complying. Also, with super slim section profiles and generally only a single web of narrow (normally around 1/8” thick) steel running from front to back on each profile – the actual amount of heat loss is also greatly reduced. Compounded with the low heat transference, this leaves a product with thermal insulation properties are generally very good – without the need for thermal breaks. We try and steer away from thermal break in steel window because as soon as they are introduced, there is of course a loss of profile strength, and it is this inherent strength which is the key point to being able to produce slim profile window walling.
It must also be worth noting that due to the small section profiles, more sun energy is absorbed by the building as a result in comparison the larger-profiled systems such as aluminum and vinyl. Coupled with IGU’s generally either 5/8”, ¾” or 1 1/8” thick – this gives the scope to use high energy efficient glass units, and with integrated weather stripping on the opening windows – heat loss through gaps in openers is a thing of the past.
And lastly, whilst we are on energy conservation, please also bear in mind that (our) steel windows are rolled from 100% content recycled billet steel, which can also be recycled at the end of its long life (a life that is especially lengthened by our hot dipped galvanizing and polyester powder coating).
So, not only do they look fantastic as can be clearly seen in Bud’s photos, they are a very good product in terms of efficiency. It is not always down to just the U factors.
There are a few known problems though with fibreglass. The biggest is cost. It is widely known that fibreglass windows are very expensive in comparison with other materials.
Also, it is when you get to fine details that the differences are evident and the real selling point of steel strand to the forefront. One of the beauties of mild steel is that all frame corners are welded, galvanized and powder coated to form a complete unbroken surface around the frame. Fibreglass windows are still mechanically jointed and therefore not only do you see that break point - you also lose a fair amount of structural integrity with larger openers not being possible as a result. The surface of fibre glass is of course relatively "hard" which is good for surface finishing, but with (and I may get corrected here!) air drying paints. On the opposite side of the scale, mild steel will always hold its electrostatic applied thermosetting polyester powder coating much better than applied finish to fibre glass, which of course lengthens the maintenance cycles and thus reduces on-going costs when using steel. Added to the very high cost of the windows to begin with makes the choice of fibreglass for specifiers difficult to sustain and justify when the firm costs come in.
Another key point is the holding of fasteners (hardware, handles, hinges and the like) to the frame members. Steel obviously once drilled and tapped offers a secure sound thread to hold such items. Fibreglass, although better than vinyl, will never hold a fixing as well. Therefore it can be safely argued that the service life maintenance level involving re-fixing of hardware, corner cleats fixings, hinges will be higher in fibreglass than in steel.
There is absolutely nothing wrong with using fibreglass as a window material and actually fits our ethos of strength, finesse and longevity (to a point) - but we would pose the questions: why pay more money for something that almost looks as good, almost lasts as long, almost has as small a profile section and almost performs as well - when the real deal can be had for less, will last longer and will perform better?....
They are essentially commercial windows that you see in most store fronts throughout the USA.
There are two types standard and we're going with thermally broken frames. I didn't get how until I met with a glaizer and he showed a section where the have a composite material that ties the metal on the outside to the metal on the inside of house which doesn't allow the cold or heat to transfer through since there's metal-composite materials-metal. It's certainly not perfect I'm sure but I've heard it's a significant efficiency gain.
We're also paying to have insulation blown into the box section/open part of the hidden frame which will make a significant difference. The window supplier recommends this for residential applications since the HVAC needs are different than commercial.
In total, the thermally broken, metal, insulation option is extremely expensive but the look is stunning. Another reason we didn't break ground yet and socking away every nickel we can...but it will be worth it....until my wife finds out no Chanel purse for Xmas this year.
ASTM E1996 - 12 Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Windborne Debris in Hurricanes
E 1886-02, Test Method for Performance of Exterior Windows, Curtain Walls, Doors, and Storm Shutters Impacted by Missiles and Exposed to Cyclic Pressure Differentials
For Missile Level D / Wind Zone 3.
As a side note, this is another key selling point of using mild steel windows and doors. The inherent strength of the profiles mean that we do not have to increase profile sizes exponentially to deal with increased required resistance to wind, water and air penetration - in addition to enhanced impact resistance.
(On a side note: One must put aside some prices of historic local US mild steel window manufacturers and associated prices. We have been exporting steel windows from the UK for many years and over 160 years of manufacture have shown us how to make these not only to exceptionally high quality - but also to economical prices in comparison to more known US manufacturers. Lead in times are also lower, even with 2 weeks sea freight)
Our established US distributor network sell other material products such as wood, aluminium, bronze and clad windows and so constantly feed us comparative prices for our product vs. other materials. This enables us to gauge price point against other products.
We are not saying it is a cheap product, but it can be very cost effective for the correct building. And what it can add to the finished build is, of course, priceless!
Thanks for all the great info, and I can certainly appreciate all the benefits of steel as a sustainable material and its thermal properties that you have mentioned, but ultimately it is the U-value that we have to comply with here in Oz, so it would be great to get some info from your distributor, cheers
http://www.crittall-windows.co.uk/news/1/76/windows-on-the-world.html
Or feel free to contact me. Roland@allaboutwindowsssc.com
Has there been any further advancement in the quality of steel windows when they're delivered? Are they available glazed? Do they have nailing fins?
Pitting is usually the result of insufficient de-gassing of the surface of the product prior to coating with the finish. If not de-gassed, the air will expand under heat (usually during thermo setting) and this can "pop" open through the surface finish - leaving a pit or hole. Not very attractive. We have spent many years as an approved applicator for Akzo Nobel Interpon Polyester Powder Coatings, and you would not believe the number of pre-treatments that are required prior to coating! Expensive, time consuming but absolutely necessary to attain the correct finish. If it doesn't come out of the oven to an acceptable certified standard, the windows windows should not get past Quality Assurance procedures, and should be stripped and re-done.
In regard to nailing fins, these are not appropriate for steel windows due to their weight. Steel windows must either be screwed directly into the structure through the frame, or they can be fixed with "Z" shaped fixing clips. All our steel windows have purposed made fixings to suit the application - either simple countersunk fixing holes to the perimeter, or with "Z" fixing clips/lugs that attach to pre-drilled/tapped fixing holes on the window perimeter (using supplied machine screws). The installer then simply makes the fixing to the structure through the other end of the "Z" clip/lug through a pre-drilled hole. The clips/lugs are all rustproofed after drilling holes and forming them. All lugs/clips are sized to suit the structural surround details, and all are constructed from steel.
In regard to factory glazing then there are very good reasons why steel windows and doors are glazed in the field. The first is the weight. Steel windows and doors weight more than your average window and therefore if they were factory glazed - the handling in the field would be difficult and dangerous - especially with large frame windows for which steel is synonymous. The second reason is that due to the slim line front-to-back dimensions of steel windows - the fixings run through the profile directly under the edge of the glass, meaning that the glass must go in after the fixing has been made.
Hope this helps, and hope you will use steel windows again in the future, albeit through another supplier ;)
They have 3 different frame profiles, that allow them to produce Sightline Window/door Units in both True Divided light and Simulated Divided light configurations. Their largest profile allows for curtain wall applications "Commerical store front" modern type of design.
Frames are fabricated in Painted Steel, Solid Bronze, Stainless Steel, and Cor-ten.
Brombal is also under going Impact rated testing of their units for Miami Dade.
If interested give me a call as we are a regional dealer located in the Eastern USA. thanks
roland roland@allaboutwindowssc.com
I am responding for a couple reasons.
1) We are the preferred Hopes Installing Dealer for the west coast of Florida / Tampa Bay Area. If there are any questions you have on a Hopes product please feel free to contact us.
2) We now have the U.S. Patent Pending for the first ever structural (butt glaze) glazed impact-resistant glass system for exterior residential and commercial applications. This provides a completely un-obstructed view with the peace of mind of impact resistance.
Our Slimpact product is completely frame-less, with glass viewing areas 10' tall by any width.
ASTM E 1996 Missile D tested / Zone 3 with 60 PSF design pressures.
If you are in an impact zone, and you do not want to compromise on restricting your view, Our Slimpact system will provide the best un-obstructed view.
If you have any questions please feel free to visit our website (being updated currently) or contact me directly.
With all design, it is of course finding that compromise between good design, and desirable performance levels. Steel windows offer that compromise, and with good design (large pane windows with simulated divided light muntin lites where required / Only using larger profile operable windows where really required, etc.) class leading thermal insulations values can be achieved.
If you are at all worried please do drop me an email with any inquiry you may have and we would be happy to computer simulate out projected U factors for a specific project.