Windows are designed to be look through, but occasionally, we look at them. What we see depends on our perspective. Architects may see the design, building scientists will look for air or water leaks, the cleaning staff will immediately assess the difficulty of reaching all the panes. Windows are often the battleground for preservationists vs energy retrofits, with several myths promulgated by both camps.
Myth 1: Historical windows are always better. According to the National Register of Historic Places, the minimum age for historical is 50 years. In 1966, when the agency was established, this timeline would have referred to buildings from 1916 and earlier. Windows would have been built out of solid heartwood, possibly designed with removable interior sash stops, allowing for full access for cleaning, repair or replacement. However, a 50 yr old building also now includes the “mid-century” homes, some of which had single-pane aluminum crank-out windows. One would be hard pressed to figure out anyway in which these would be better than a replacement energy efficient window.
Myth 2: New windows are always worse. This referred to vinyl and aluminum windows, which don’t have the longevity of wood, nor could they match the look. However, the new pultruded fiberglass windows have a narrower profile similar to wood, can be purchased with exterior muntins to simulate divided lite panes, and very low heat conductivity. From an environmental standpoint, fiberglass takes the least amount of energy to produce and has the longest life expectancy of any window frame material. This provides an option which satisfies both historical integrity and energy concerns.
Debunking the myths, what is the best way to proceed? Decided if the window style is an intrinsic part of the existing architectural design, or the intended design of the remodel. Not every old building is historical or architecturally pleasing. Can the windows be repaired or improved for air and water sealing? (link to the retrofit of the Empire State Building) Existing fixed windows from the 60’s can often be left in place, supplemented by an additional fixed double pane on the interior. Interior storms can provide the extra protection while retaining the historical exterior of operable windows. And if the decision is to replace new windows, spring for high quality, energy efficient, long service life. Make sure they are installed with proper flashing and window pans. This is a big investment which you don’t want to have to revisit in 10 years time. This is an investment not only in energy savings, but comfort, ease of maintenance, and functionality. What you see is what you get.