Mark Meshulam is an exterior facade consultant based in Chicago, IL, USA

Live again, steel window!

To many of us in the construction field, building is rewarding. Seeing a hard-sought finally-completed product gives a sense of accomplishment and fulfillment difficult to obtain elsewhere in life, unless you are writing web postings such as this one. That’s fun too. A uniquely rewarding part of construction is the restoration of beautiful architectural features made long ago, giving them new life so they may live yet again. Dr. Frankenstein must have felt this way too, as he exhorted his creation, “Live! Live! I give you life!”

Of the many beautiful architectural features, the only one you can see through is the windows. Ok, railings qualify too. But windows are the eyes into the soul of the building. They give a structure personality the way eyes give personality to the face. Old-time windows have an old-time personality that fits the old-time facade.

Rarely photographed with goggles over her eyes, Amelia Earhart knew that the wrong windows could harm the beauty of the structure

If you change windows without care, your building can suffer a permanent degradation. It’s like putting swimming goggles on a beautiful lady, except she can take them off. A decision to restore your windows, rather than replace them, may be the right choice from an architectural and economic standpoint.

Until the late 1940′s, the materials of choice for window frames was steel or wood. Later, aluminum, vinyl and clad wood came on the scene to displace those venerable materials. Steel windows became obsolete because aluminum offered greater versatility in cross-sectional shape due to the extrusion process. With extruding, the dimensions of that shape are accurate to within thousandths of an inch. Extruded aluminum parts can mate with one another tightly, snap together, receive screws along their length and can even be fitted with thermal breaks. The poor steel window, made with a hot-rolled or cold-rolled process, could not compete in either tolerances, flatness or intricacy.

Steel window section at left is far simpler than the thermally broken aluminum section at right, but it has strength, so it is easy to restore, and narrow sightlines

Steel windows still retain the advantages that make them attractive to aficionados of old buildings: The are very strong, allowing small sightlines. It’s relatively easy to restore steel windows because of their strength and durability. A hallmark of a rolled-section steel windows is thin frames and multiple lites. When you buy your new windows with in-glass muntins, you are paying tribute to the beauty of small sightlines and multiple lites found in steel windows. Whether the public accepts in-glass muntins as enhancers of a building’s beauty will be left to the eye of the beholder. But steel windows are the real thing.

Real steel casement at left is emulated by wood-clad casement on right. Although the in-glass muntin is narrow, being behind the glass weakens the impression of a true divided lite window. Heavy perimeter frame conflicts with the airy muntin look

The downfall of steel windows has come in part with the rise in energy consciousness – most steel windows are single glazed and have no weatherstripping to speak of. So, unless you restore your steel windows with strategies to counteract these shortcomings, occupants will freeze, sweat and pay far too much for heating and cooling.

A fixed hollow metal steel window

In addition to rolled-section steel for windows, what is known as “hollow metal” is also used. Hollow metal is simply sheet metal that has been sheared to strips of a needed width, then sent through a succession of rollers that impart a desired cross sectional shape. Hollow metal is used even today for doors and door frames where a fire rating or high durability are required. In contrast to rolled section steel windows, hollow metal steel windows tend to have bulky sightlines. But these too can fit their surroundings very well, as we will soon see.

Let’s look at two steel window restorations we performed, one with rolled section and on with hollow metal.

Penthouse Private Residence, Chicago

Restoring steel windows 130 feet in the air from a swing stage. This required special permits, a sidewalk canopy and special rigging on the roof

Steel window restoration performed carefully in close proximity to high value finishes

This elaborately decorated residence (see background image), with a commanding view of Lake Michigan and Lincoln Park suffered from decaying steel windows. The original intention was to remove the entire windows from the site, remove the glass, shot-blast, powder coat, reglaze with insulated glass and reinstall with new weatherstripping and caulk. But things don’t always go as planned. The frames were deeply anchored into the structure, and removal was blocked by terra cotta on the outside and extensive oak casework on the inside. One might ask, shouldn’t Chicago Window Expert have figured that out ahead of time? If asked this question, he might have answered, “it’s the survival of these types of experiences that have made him an expert.” Better to not ask, though.

The plan was changed so that all of the restorations listed above were performed on the operable casement sash, but the perimeter steel window frames and fixed frames were to be restored on site. This was not easy 130 feet in the air from a swing stage with priceless artifacts only a few feet away on the inside. Plexiglas was cut to size and repeatedly removed and reinstalled as each operation was performed. The off-site operations went very well due to the ease of working in controlled environments. The site work took too long and the finish was less smooth than the factory finish. But we got the job done, and the windows are positioned to last for many years to come.

This steel casement hardware could be called a sash limiter or friction device. It needed a facelift as much as the windows

The bronze casement hardware responded well to spruce-up. In some cases missing parts were machined from scratch

Shot blasting is an effective way to remove layers of old paint and expose the beauty beneath. Care must be taken to use a shot that is not too aggressive to avoid damaging the steel windows. Following the shot blasting, the windows were painted in a powder-coating plant. Powder coating is a process that uses high heat to fuse the paint to the metal. Finish smoothness and durability are quite good.

Deteriorated steel window frame (left) gets a facelift with the help of shot-blasting, revealing a rugged, uniform color and texture beneath

After shotblasting, steel windows received a powdercoat finish in this facility. After pretreatments, the powder coating is applied to the frames and baked on

The windows were then glazed with insulated glass using a two-part rapid cure structural silicone, applied by skilled craftsmen and tooled on a bevel to look like putty glazing

Old Main Post Office, Chicago
Built in 1932, this 2.5 million square foot iconic building was designed by architects Graham, Anderson, Probst and White. It was bought in auction by English real estate developer William Davies in 2009. It is so big, the Eisenhower expressway runs under it. It is listed in the National Register of Historic Places. I have spent many hours in this incredible behemoth.

Old Main Post Office, Chicago

The windows are hollow metal double hung and unique hollow metal triple hung. Massive weights reside in the jambs to counterbalance all sash, including the top of the triple hung. Their strictly-business institutional look perfectly complements the acres of architectural limestone surrounding them.

Before and after restoration of hollow metal steel windows at Old Main Post Office

The sash were taken off site, shot blasted, spray painted and reglazed with monolithic glass. The frames were ground smooth and spray painted. Although not a part of the scope, there are instances on the building where frame portions are rusted through. In this case the material would be replaced with like material, smoothed to the greatest extent, and painted to match.

Restored steel window at center is flanked by non-restored windows

Considerations
When embarking upon a project to restore steel windows, here are some things to consider:
1. Are there any historic designations or historic tax credits in place for the property? If so, it will be important to get in contact with the involved governmental parties and clarify the parameters of the project. See this article for more: An Interview with Historic Mike Jackson.

2. Will there be a need to improve U value? How will that be accomplished? Can insulated glass be added to the existing frame, or will a new additional frame such as a storm window be needed? If an exterior storm window is planned, will it fit the historic look of the building?

3. Similarly, is there a need to improve air infiltration? This can be extremely difficult on some types of windows. There may be a need for a cycle of test/repair/test to find the right solution.

4. Are some parts of the existing steel windows completely destroyed or rotted through? If so, mockups of the proposed repair method will be needed before embarking on the entire project.

5. Do all windows on the building need the historic treatment? I have seen compromises made with historic agencies wherein they will allow approaches that are not strictly historic in areas of the building considered less important.

6. Do your steel windows have lead paint or asbestos caulk? Use an expert to help formulate your strategy to address these conditions. There may be a need to segregate work areas in order to perform remediations and mitigations. These tasks must be fitted into your project schedule. Mockups can be useful here also, as the involved parties get an opportunity to see the extent of the work and gain expectations for the end result.

7. Is there a need to discover and match the original paint color? There are experts who perform this type of work. Here are some specs for this from the GSA.

Resources
The Repair and Thermal Upgrading of Historic Steel Windows, Technical Preservation Services, National Park Service, US Department of the Interior
1931 Popular Science article “Biggest Post Office to be Built in Chicago”
Emporis Listing: Chicago Old Main Post Office
Northwestern University Article “Booth Designer of Chicago Old Main Post Office Building Redevelopment Project”

Want to restore steel windows?

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