We have storm windows on the outside of the original windows on our century-old house in Denver. From inside our home, I get to enjoy the wavy character of the old glass and the beauty of the old wood. I try to discourage neighbors and friends from window replacement, and encourage them to get storm windows instead. LEED® encourages window replacement, but it shouldn’t. Here’s why, taken straight from a publication by the National Institute of Building Sciences:
“LEED® fails to acknowledge that historic windows are important features and that their energy efficiency can be upgraded. LEED® encourages the use of highly energy efficient windows, which often requires the removal of historic windows that are potentially reusable. Moreover, original windows are character-defining features of historic buildings and their removal can significantly alter a structure’s integrity, thus conflicting with preservation goals and the Secretary’s Standards.
“With proper maintenance, windows built from old growth wood can function indefinitely and their performance can be substantially bolstered by using storm windows, caulk, and weather-stripping. Studies have shown that these simple improvements can result in efficiency similar to that of new insulated glass windows. Modern windows also have a relatively short lifespan and can be difficult, if not impossible, to repair. Once modern windows fail, there are few ways they can be recycled, and they will likely end up in landfills. This begins an environmentally insensitive cycle of removal and replacement.
“Therefore, the most responsible approach is to retain historic windows that last and retrofit them with increased effectiveness rather than install new windows that, without exception, will fail and cannot be repaired. Regrettably, the replacement window industry is strong, and old windows are touted as poor performers, so the common practice of replacing windows in not likely to change much in the immediate future. To combat this, LEED® should consider awarding points for the repair and continued use of old windows where significant improvements in energy efficiency are demonstrated, as well as where significant amounts of historic fabric are being retained and reused.” - National Institute of Building Sciences, Whole Building Design Guide, WBDG13 “Strategies for Sustainable Historic Preservation”
The bold text above highlights the important issue. The most sustainable thing to use is what you already have, especially when it’s as precious as a historic window.