It's impossible to calculate how many original windows in Hudson's historic buildings have been removed and trashed in the pursuit of promised energy efficiency. The practice is still going on, a notable example being the Columbia County courthouse. Meanwhile, there is growing evidence that original windows can be just as energy efficient as replacement windows, the life expectancy of replacement windows does not compare with that of original windows, and replacement windows do not pay for themselves in energy savings before they have to be replaced again. Joining the body of evidence is a report from the National Trust for Historic Preservation's Preservation Green Lab entitled Saving Windows, Saving Money.
Earlier this week, the National Trust published, in its Preservation Tips and Tools series, useful information about preserving old windows in a feature entitled "Retrofitting Historic Windows."