Original wood windows are an important architectural element of any historic structure. They serve as the "eyes" of the building, reflecting a level of craftsmanship that can’t be matched with substitute materials. In my experience renovating and selling historic homes, I’ve found that most buyers appreciate the historic integrity of an older home with original wood windows that function properly, and they’re willing to pay a premium for that integrity. That’s why I recommend repairing inoperable, original wood windows whenever possible. Windows with broken panes, windows that stick, windows that won’t stay open and windows with broken latches or sash cords can all be repaired. There may be a cost involved, but it’s generally less than the cost of full replacement. If and when an original wood window is beyond repair, I recommend replacing it with a new wood sash window.
Despite the clear value of original wood windows, many homeowners choose to replace them with vinyl windows because they believe they’re less expensive and more energy efficient. The evidence actually shows that replacing wood windows with vinyl can be a costly mistake, in large part because they’re not ultimately “maintenance-free.”
It's true that vinyl windows don't need to be painted, but their seals often fail. Vinyl isn’t as rigid as wood so it shrinks more in cold weather and expands more in hot. In fact, vinyl expands twice as much as wood in hot weather and seven times as much as glass. That’s why the seals between double and triple panes of glass fail so easily with vinyl windows. The risk of failure only increases with the size of the window.
Many people think vinyl windows will last forever, but the International Association of Home Inspectors cites an anticipated life expectancy of just 15-20 years. That’s consistent with what we’ve observed selling houses that were built in the 80s or 90s, where it’s not uncommon to find multiple windows with failed seals. Repair isn’t possible with vinyl windows. Replacement is your only option.
Another “selling point” of vinyl windows is the energy efficiency associated with double or triple panes and glazing. In point of fact, insulated glass doesn’t help that much with energy efficiency because approximately 85% of heat loss occurs around the edges of the sash, not through the glass. Any energy savings associated with the replacement of single glazed windows with insulated ones is unlikely to justify the cost of replacement, particularly given the relatively short life expectancy of vinyl replacement windows (see above).
If you’re interested in increasing the energy efficiency of your single glazed wood windows, consider fitting them with storm windows instead. According to a study issued by Preservation Green Lab in 2012, a single glazed wood window with a fitted storm window offers 92% of the energy efficiency of a vinyl window (see chart below). The bonus? Wood windows last 6-8 times longer than vinyl – so again, any small gain in energy efficiency is lost to replacement costs.
Take home message? Don’t replace wood windows with vinyl. It’s just not worth it – on multiple levels.