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Lessons from Henry Street: Historic Windows — Repair or Replace?

henry street windowThe MAS demonstration project at the Henry Street Settlement has led us to the conclusion that repairing, versus replacing historic windows may help reduce air drafts in a more cost effective and historically sensitive way. While the Settlement still has many historic, single-pane windows, some of the original windows across the rear façade have been replaced. Our team discovered that these replacement windows leak air and are drafty, showing that new windows are not always better than old windows. There are ways to make historic windows more energy efficient besides replacing the windows—for instance, historic windows can be outfitted with interior storm windows, which provide a layer of insulation and can help improve the window’s thermal efficiency.  We decided to put this method to the test at the Henry Street Settlement. To begin, our team performed a host of tests as a baseline to measure the current performance of the historic windows and to indicate where the drafts were coming from. Two of the windows will be fitted with storm windows in the coming weeks, and we will repeat the tests to determine the efficiency of the storm windows and if they are an effective solution.

Why Replacing Windows Almost Never Pays

New windows are expensive. Repairing existing windows is less expensive than replacing them and helps retain the historic integrity of the building. The most common complaint about new windows is that they are installed poorly.  Warrantees are short and usually do not cover installation (and post-installation) issues. New windows reduce the amount of glass—and therefore light— that enters the room.  Because new framing and mullions (wood pieces that separate the glass panes) hold multiple panes of glass they are wider than those found in older windows, the net result is reduced glass—often as much as 20% less glass—and therefore less light. It is environmentally sound to repair and install interior or exterior storm windows; that way, old material is not wasted and lesser amounts of new material is used. For more information on how to preserve historic windows, visit http://law.du.edu/images/uploads/rmlui/conferencematerials/2009/Wood%20windows%20NTHP%20tips.pdf