The breakthrough came on a Saturday. I was participating in the Ask Andrea Hip Home Improvement radio show, a program focused especially on energy efficiency and green building. I was there to add the preservation perspective. One of the guests was a contractor known for his experience with green building and during the course of his time he was asked about energy efficiency improvements to old wood windows. In a market flooded by the conviction that existing old windows should be replaced by new windows that use double glazing (insulating glass units), I was shocked by what he said; " Well, of course, the primary problem with old windows in this part of the Country is air infiltration..." Precisely the message that I and others experienced in preservation had been preaching for some years. This marked the first time that I heard such a proclamation from someone outside of the preservation field.
Historic wooden windows, especially double hung, do a pretty good job and don't perform that much differently than their modern counterparts except in one area, air infiltration or air leakage. You have likely felt distinct drafts while next to these windows and have seen strong winds cause blinds and drapes to move inside the building. During the restoration of the Erath County Courthouse (Stephenville) all windows had been replaced (twice) under previous renovation efforts. Our proposal to install new windows that replicated the original historic windows was met with skepticism by the County Judge, who made it especially clear that he did not want cold drafts coming in through the new windows. The good news is that air infiltration is one of the easiest and cheapest problems to fix and certainly doesn't require window replacement.