Thanks to Bob O'Neal for bringing this article from Daily Finance to my attention. Not normally a place to find useful historic preservation information, this article recounts the recent energy upgrades performed on this most recognizable landmark. Of interest on the historic side are the windows. In the article, Bruce Watson recounts how the existing windows are retained and retrofitted to substantially improve their energy efficiency. This was not done at the mandate of the powerful New York Landmarks Preservation Commission, but to SAVE MONEY. As it turns out, they retained the existing metal sashes, frames and even the existing glass, but added a low-e film and other improvments. The result was a retrofit cost of $700 per window versus the original $2,500 per window costs when the default replacement option was considered. To me, another example of what can happen when working with design and construction team members that are not intimidated by the notion of retaining, renovating and restoring.
In fairness, there are a few questions. The article notes that the existing windows are already double paned. This suggests that they have been replaced previously, but I have so far not found information on this one way or the other. I have confirmed that the building is a listed New York City Landmark, as I knew it would be, and subject to the control of the Commission, which is not known for suffering foolish preservation attempts. So clearly, they have approved the work, right down to the color. This appears to be another contradiction to the widely held misconception that historic preservation necessarily costs more than conventional new construction.