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Window repair, restoration, or replacement is an unavoidable topic of concern in historic buildings. Windows in your historic property are like the eyes of the home. They are an important piece of the historical fabric of the location, and also play an integral part in energy efficiency of the property. Simultaneously, they are one of the most vulnerable and “at-risk” elements of our architectural heritage. Replacement is not always the most cost-effective or energy-efficient answer. Determining the extent of disrepair in your windows is your first step in deciding whether to repair, restore, or replace them. 

Photo of our restoration work on windows at Franklin Street Station in Reading. 

Why are original windows important? They are considered a significant feature of a building, making up both exterior and interior architectural elements and usually 20-to-30 percent of the surface area of the building. The shape and materials, moldings, trim and window pane arrangements are all clues to the age of the building. To further illustrate these unique characteristics, here are examples of window styles and characteristics from the 18th, 19th, and early 20th century. The majority of the features that make original windows special are not replicable in replacement windows; you could replicate them in reproduction windows, but that is not what most people think of when they are discussing replacement windows. These elements include antique (wavy) glass, true divided light sashes, and traditional joinery.

Why are original windows endangered and at-risk? Several preservation organizations, including Maine, Virginia, and New York, have noted in recent years the endangered status of historic original windows. Even we have had first-hand experience talking with well-intentioned homeowners who’ve been convinced by saavy sales people to replace their original windows with modern ones under the guise that they are more cost-effective or energy efficient, only to regret the decision a few years later when the “superior” new windows are no longer functioning properly and are incurring more costs for energy, repair, and replacement. 

Are original windows energy efficient and cost-effective? Energy efficiency is a major concern when it comes to windows. We’ve noted in a previous post on Siding on Historic Homes that heating and cooling energy loss is associated most with windows, doors, and roofs, and this is often worse with modern replacements and materials. Meanwhile, original windows have a proven track record of durability that far exceeds that of new replacement windows, as long as they are properly maintained. In fact, most are 100+ years old. The National Park Service’s Preservation Brief No. 3 and their Testing Energy Performance of Wood Windows in Cold Climates both discuss energy efficiency in greater depth. The latter of the two aforementioned resources points out that replacing historic windows does not necessarily result in greater energy savings than upgrading that same window. If you’re short on time, you may instead choose to read one of our other brief articles on energy-efficiency and cost-effectiveness of original windows. On average, the energy savings after a replacement window is installed is less than $2/year. Restoring and repairing original windows can achieve almost the same energy efficiency, and is more cost-effective in the long-run because new windows will not last as long. 

Now that you understand the significance of original windows and the importance of saving them, how do you know if your original windows are repairable or restorable? First, consider that most materials and methods used to build the original windows are made to be repairable, so there is a higher likelihood that they are salvageable. Replacement pieces can be made rather than replacing the entire unit (consider our woodwork at the formerly abandoned Franklin Street Station in Reading, PA, whose windows were in a shocking state when we first encountered them; alternatively, you can see the results in-person while enjoying craft beer and a bite to eat at Franklin Street Brew Pub now in the station). Things to evaluate to see what repairs windows might need:

  • Loose frames and sash components
  • Slipped sills
  • Poor fitting sash and storm assemblies, and misaligned frames
  • Loose, open, or decayed joints at sash or frame corners
  • Loose hardware, broken sash cords/chains, worn sash pulleys, locking difficulties
  • Deteriorated weather-stripping
  • Broken/cracked glass, loose or missing glazing putty
  • Peeling paint
  • Window well debris accumulation

Some of these issues are easy to see and address. Others, including locking difficulties and window well debris accumulation might signal a misaligned sash and could necessitate the involvement of a skilled person to make those adjustments (or at least consult with you about what to do). All of these repairs will increase the energy-efficiency of your windows.

What do I do if a previous owner already replaced the original windows and updated replacement is necessary? There are several options to choose from:

  • Rebuild with antique glass
  • Rebuild with true divided lite and insulated glass
  • Replacement with modern replacement windows – The National Park Service’s Preservation Brief No. 9 has a list of what to look for in replacement windows, as well as ideas of where to find historically sensitive replacement windows

For more information and resources:

  • Visit our window post archives link
  • We typically recommend 2 Canadian manufacturers for modern replacement windows: Norwood Windows or Loewen

Authors

About Danielle Keperling

Danielle Groshong-Keperling has worked full-time in the restoration industry since 2001, but her education in the traditional trades, construction industry, and historical preservation was built from an early age through her Father's work in the traditional trades and her Mother's love of historic architecture. Now, with Jonathan (an artisan craftsman in his own right), her partner in business and life, they work together to help historic building owners restore and preserve their piece of our built history.

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