Updated: Apr 27, 2020
There are good reasons to replace old windows. Probably the biggest reason is they are double-paned which means you don’t have to hassle with storm windows. They operate easily and many tilt out for easy cleaning. Plus, most are vinyl or wood clad with vinyl on the outside—vinyl never needs painting. Other alternatives are aluminum or fiberglass.
The thing is, if you think replacement windows will pay for themselves in energy savings you’re in for a disappointment. On average, new double pane windows are about twice as efficient as old single panes but only about 15 percent more efficient than single panes with storm windows. Since windows comprise only a relatively small portion of a house’s envelope you’ll see only a 5 to 10 percent energy savings. At that rate, it could take a century to recoup the cost of new windows. And while you don’t need to paint vinyl--in fact you can’t--the reality is that sun and temperature changes will destroy them 20 to 40 years depending on conditions and window quality.
Nowadays, when windows are made of wood, they usually are clad with vinyl on the outside. That’s because new wood just can’t stand up to moisture, even when painted. Windows built before around 1930 are likely to be old-growth longleaf pine. This wood was much stronger and much more resistant to rot than new wood. In fact longleaf was used extensively in old house construction—one big advantage over new homes. The point is, when maintained, old windows can last several lifetimes.
If you are looking to put some sweat equity into fixing up an old house, old windows are a great place to get your feet wet. Unless the windows are really shot, most repairs require more elbow grease than skill. The most common repair is scraping out and replacing the sash putty—a job that’s easy to do. And when a baseball sails through a new window you’re looking replacing a whole window. With old windows, you can get a piece of glass cut at your local hardware or glass store, get out the putty and fix it yourself.
Many times old windows don’t work because the sash weight cords are broken. These cords were attached to counterweights in pockets next to the windows and they made it easy to raise the window. Sometimes the weights are deliberately removed by misguided renovators who think that insulating the pockets will make the house more energy efficient—in fact it does help a little, though not enough to justify ruining the windows. If insulation was just stuffed into the pockets this can be reversed easily enough. If expanding foam was used, that’s a good argument for new windows.
Let’s talk a little more about the other big argument for new windows—eliminating old storm windows. Usually that means those ugly knuckle-busting aluminum-frame storms. Or it means the more traditional heavy removable wooden frames that can require a ladder to install. We had those wooden monsters in the first old house I owned. I found all the storms in the shed. And because window sizes varied, a previous owner had carefully labeled each one with which window it fit. The labels were “Jim’s left window.” Or Sally’s middle window.” Unfortunately I never met Jim or Sally.
Today you can purchase interior storms. They can be glass or lightweight flexible polymer as shown here. These are relatively inexpensive and they can be used with out-swinging casement windows as well as double-hung windows. They’re relatively unobtrusive from the inside. And of course you don’t see them from the outside so they don’t disturb a historic façade.
Speaking of historic facades, nothing destroys one as effectively as the wrong new windows—especially cheaper vinyl ones that tend to have much wider frames than original windows. Inappropriate windows can actually lower the value of an older home. Window replacement should be sensitive to things like whether the original windows had divided lights and if so how many.