Mark Meshulam is an expert witness and consultant for window preservation.

In a continuation of our 20 year retrospective of our unique historic window replacement at Chicago’s Field Museum of Natural History, we have dusted off never before seen video of the design and testing of the project, jazzed it up with some editing and have posted it here for your edificial edification.

Historic window renovation is a special corner of the window business, and it is one of my favorites. It requires a level of field surveying that is beyond the level required by typical window replacement. It might involve the stabilization and restoration of existing materials, it might involve replicating certain components, it might involve retrofitting energy efficient properties to the existing system. Historic window renovation might even involve complete window replacement, as is the case at the Field Museum.

Precise measurements of all existing window components is a critical part of historic window renovation
Precise measurements of all existing window components is a critical part of historic window renovation

Whatever the scenario, historic window renovation requires a full understanding of the original Architectural intent and actual in-place construction. In order to accomplish a faithful replacement of components or entire assemblies, one must capture all dimensions and profiles of the original installation.

Done well, the details of the visible components of the replaced components will read nearly identical in shape and dimension to the details of the original condition.

Historical purists, as well as the U.S. Department of the Interior demand that, if existing materials can’t be repaired and restored, that these elements be replaced with “like kind” material. Wood for wood, steel for steel, you get the idea.

This philosophy can sometimes be difficult to reconcile with other building design requirements, particularly specifications for enhanced thermal performance, reduced air infiltration, increased water test pressures, acoustical attenuation, finish longevity, and of course cost.

My own philosophy? These days I am happy to get work, regardless of scope. Whatever the project requires, our company has the technical capabilities to do the work. When original ornamentation is present, it’s a shame to miss the opportunity to refurbish that ornamentation to its original glory. There is value in restoring original materials, and challenges involved with adding new features and benefits to an original historic core.
Historic window renovation can involve castings
The part of the historic window renovation philosophy that bothers me is the aspect of longevity. As we can see at the Field Museum 20 years later, the windows and castings look every bit as good today as they did 20 years ago, with absolutely no maintenance or refinishing. I daresay that the same could not be said if we had used wood. Not only would wood have required repainting by now, but with each successive painting, the finish would lose some of its pristine look. Wood’s difficulty enduring the rigors of time and weather can become a liability when used with insulated glass, which requires a positive seal and a drained glass cavity.

Dimensions of wood change with humidity
Dimensions of wood change with humidity

Wood also expands and contracts with changes in humidity. This can disrupt seals and make the engineering of gaskets difficult.

Imagine this design conundrum: Wood shrinks radially and tangentially (both directions affect wood thickness) in low humidity. Winters tend to be dry. Winter is when you need tight gaskets in order to reduce energy loss.

With gaskets mounted between wood elements, such as between sash and frame, the gaskets will be compressed LESS in the winter.Wood radial and tangential dimensions

Speaking of gaskets, wood and steel windows have severe limitations with regard to positively capturing a gasket. Aluminum has the ability to be designed with “gasket raceways” which are extruded especially to hold a gasket in a precise operating position.

Aluminum can be extruded or formed so that it is nearly identical in shape to the original wood or steel windows. If it is nearly identical, and lasts so much longer, why not use it? When a person looks at a window, they don’t know that material it is made from unless they start knocking.

Preservation Chicago Window Restoration vs. Replacement Studies

The Repair of Historic Wooden Windows. Technical Preservation Services, National Park Service, U.S. Department of the Interior

The Repair and Thermal Upgrading of Historic Steel Windows Technical Preservation Services, National Park Service, U.S. Department of the Interior

The Secretary of the Interior’s Standards for Rehabilitation

Want to talk about historic window renovation?

Mark Meshulam, Chicago Window Expert wants to help you renovate your windows historically

11 thoughts on “Historic Window Renovation”

  1. Feldco!?!?

    Vinyl windows are an abomination! They’re “maintenance free” because they’re meant to be tossed into the land-fill when they break (everything breaks).

    What does “freedom from maintenance” buy us? Another day in front of the boob tube to, quote my grandmother, “turn [y]our brain[s] into mush”?

    According to a number of studies, the heat loss from windows is negligible. Most heat out-migration is through the ceiling and roofs. Some added insulation and your golden.

    Wood windows are often, in cities like Chicago, St. Louis, Milwaukee, etc, made of old growth wood, which today is priceless. Why is it priceless? Because there are no old-growth forests left. Its an absolutely cussed act to toss these into the land-fill.

    Though folks passing by, or even stopping to admire may not knock on the window to assess material, we, as a society, know what our built environment is made of.

    Our built environment is, and should be a reflection of who “We” are. We are what we build.

    Who/What do we want to be? What do we want to leave future generations?

  2. Mark, great article, really love your work. Thanks.

  3. Pingback: film izle
  4. Great site! I’ve been in the window business for a while and I actually learned a few new things here….keep up the great work.

  5. I can’t agree more with M.W. Brown, vinyl windows are terrible. Just like aluminum replacement windows vinyl will hopefully be a product of the past. Very nice and informative site though. Keep it up!

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