Especially this time of year, as thermometers everywhere register remarkably low temperatures, owners of historic buildings might begin to wonder if they should just go ahead and get rid of those “drafty, old” windows after all. On cold days, the air next to windows and doors naturally feels colder, but, the reality is, these openings are not the major offenders. In fact, energy consumption and loss studies regularly show that the vast majority of air exchange in a house – collectively totaling more than 75% – takes place through ceilings, walls, floors and various gaps that allow for air infiltration, while windows and doors account for only slightly more than 20% of a home’s air loss. Moreover, while there are a number of efforts one can undertake to cut in to the “75% list” (many of which were discussed in the prior two installments of “Preservation Spotlight” in August and September 2014), there are also retrofits that can improve your historic windows’ energy efficiency while at the same time delivering a much greater return on your investment than replacement windows.
In 2012, the Preservation Green Lab (a project of the National Trust for Historic Preservation) published a report entitled “Saving Windows, Saving Money,” which concluded that “a number of existing window retrofit strategies come very close to the energy performance of high-performance replacement windows at a fraction of the cost.” The analysis focused on five primary retrofit techniques and examined their effectiveness across various climate regions to determine which techniques were most effective where; the results were compared to the option of window replacement across these same regions. The five retrofits surveyed included: weather stripping, interior surface film + weather stripping, insulating cellular shades, exterior storm windows, and interior window panels. While the study concluded that no single retrofit can provide greater energy savings than replacement windows, it also clearly shows that a combination of 2 or more retrofits can achieve equal or greater energy savings as replacement windows while at the same time providing much greater cost savings.
The idea behind all of the retrofits mentioned above is either to keep outside air out or to keep conditioned air in, and the fact that they can provide economic value by reducing a building’s air loss is certainly a good thing. But, in considering the value of your historic windows, you must also consider historic value, as well as material quality and embodied energy. The word “façade” derives from the Latin for “face”, and “window” derives from the Latin word “fenestra”, which can refer to an opening in the skull, or an eye. So it is no wonder that windows are often considered the eyes of a house – or perhaps you prefer the cliché, “eyes are windows to the soul.” As for quality, because many historic windows are built from old-growth wood, the material quality of most original windows exceeds that of even high-quality replica historic windows. Moreover, the feasibility of repairing vinyl replacement windows once they begin to fail is almost nonexistent, while wood windows that are properly maintained can last for hundreds of years, like those at the Seibels House or the Hampton-Preston Mansion in Columbia, S.C.