Should Old Windows Be Saved?

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Nearly every owner of a home with original wood or metal windows asks this question. There are some strongly felt arguments on both sides of the issue. Typically, those of us who work on old homes with an eye toward preservation will try our best to save old windows at every opportunity. But those who are looking for financial savings and energy efficiency as their top goals may be surprised to learn that rehabbing old windows can yield energy savings just as good as replacement windows would, and at a fraction of the cost. Here’s a roundup of some things to consider:

This Old House is not always the best source for preservation-minded renovation. They have a mixed reputation for going with modern solutions that don’t always remain true to the home’s historic character, especially where window rehab vs. replacement is concerned. But in their article, “Saving Old Windows,” they lay out some of the reasons windows can be inefficient and how those things can be fixed rather than replaced and why it’s a good idea to value those original materials.

” Just below a surface of peeling paint may lie some quality old-growth wood.

Saving objects made from such wood makes a lot of sense. In ancient forests trees grow slow and straight, fighting for light and nutrients. America’s older buildings are built from lumber that came from the virgin forests the early settlers found growing here. With up to 30 growth rings per inch, this clear and dense wood is superior in stability and decay resistance to today’s commercially available lumber.”

An article in Traditional Building Magazine explains the different rating systems used to evaluate window performance. Specifically, it discusses the misleading use of these numbers by replacement window manufacturers and helps level the playing field for homeowners making the comparison.

“While it is true that in response to the misuse of “U” values, the NFRC has been engaged in the testing and evaluation of whole window assemblies, what is not said is that every manufacturer has the option of discounting – and not revealing – two important markers: infiltration and condensation.

Simply put, that means that a consumer may very well be purchasing a replacement window system that allows as much or more infiltration as their existing windows. While in the past, the argument favoring historic windows was largely based on anecdotal information, preservationists have tools already at their disposal to discount replacement window arguments: namely, standardized tests defined by the American Society for Testing & Materials (ASTM) that allow for both field and laboratory testing of infiltration.”

In 2010, the magazine Fine Homebuilding took on the question in an article called “Should Your Old Windows Be Saved?” and gave some good tips for comparison and suggestions for fixes to specific problems. (A link to the original article can be found on Chicago Green Windows’ website:

“There is good news if your old home still has its original wood windows: They were built to be repaired… Restoring and upgrading old windows isn’t cheap, but much of the expense is paid in sweat if you’re willing to do the work yourself. According to Mortimer, a professional may charge around $200 for a  complete restoration and upgrade of each window—maybe more, depending on the damage. However, if you do the work yourself, you can generally expect to pay less than $100 for materials. A storm window can cost as little as $80 or in excess of $300. Again, the upgrade can cost much less if you build your own.”

In a study referenced in the Fine Homebuilding article, scientists tested six leaky wood windows. They performed various upgrades to them, including replacing one with a modern vinyl insert. As far as energy performance goes, these were their findings:

“Estimated savings for first year energy costs show little variability between upgrade options when compared to the estimated energy costs of a typical window…Estimated first year savings are also of very small magnitude when compared with typical windows. It is therefore not worthwhile to base upgrade decisions solely or even primarily on energy  considerations. Other non-energy considerations should play a greater role in deciding whether to upgrade or replace existing windows. Energy performance should be included as part of the decision making process, however. Life cycle costs of window upgrades should also be considered, including maintenance costs over time.”

Other things that should be taken into consideration are the materials used in vinyl window production. This study by award winning biologist, Joseph Thornton, Ph.D., explains their effects in his paper, “Environmental Impacts of Polyvinyl Chloride (PVC) Building Materials:” 

“By-products of PVC production are highly persistent, bioaccumulative, and toxic… In addition, a very large portion of these mixtures consists of chemicals that have not yet been identified or tested. Many of the by-products of the vinyl lifecycle are of great concern, because of their persistent bioaccumulative toxicity.”

The National Parks Service has established a set of guidelines for restoring and renovating existing structures and they pay special attention to windows. Their Technical Preservation Services department has compiled a brief list of guidelines, which includes in its list of recommendations:

  • Retaining and repairing historic windows when deteriorated.
  • Weather stripping and caulking historic windows, when appropriate, to make them weather tight.Installing interior or exterior storm windows or panels that are compatible with existing historic windows.
  • Installing compatible and energy-efficient replacement windows that match the appearance, size, design, proportion and profile of the existing historic windows and that are also durable, repairable and recyclable, when existing windows are too deteriorated to repair.
  • Retrofitting historic windows with high-performance glazing or clear film, when possible, and only if the historic character can be maintained.
  • Installing clear, low-emissivity (low-e) glass or film without noticeable color in historically-clear windows to reduce solar heat gain.

When these guidelines are used in evaluating whether your windows should be repaired or replaced, we then start to think about the question not in terms of either/or, but rather as a continuum of options in window rehabilitating. Houses rarely benefit from black and white extremes in any direction. Therefore, an approach to a house’s windows should include careful consideration of all of these gray-area factors.