An older wood window, when working properly, weather-stripped, and outfitted with a storm window, is just as airtight as a new window, a 2017 study found.
In an experiment at Mohawk College in Hamilton, Ontario, instructor Shannon Kyles and her team constructed a tiny house that included two new windows and two 200-year-old windows. Using a blower door test, they compared the air infiltration rate when one or the other set of windows was covered. The result? Air leakage was virtually the same.
If you also consider that historic wood windows are made of old-growth lumber, have lasted for 100 years, and could last 100 more, there’s a distinct advantage to repairing and restoring instead of replacing.