Repair Your Old Wood Windows

Thinking of replacing your windows? You're not alone. Thanks to aggressive marketing by window-replacement companies, environmentally minded owners of old homes across the country would likely place “replacing windows” high on their short list of things to do to improve the energy efficiency of their homes.

It's understandable. As Barbara Campagna of the National Trust for Historic Preservation says, “You're sitting next to a window and you're feeling cold air and your energy bills are high.” Windows are an easy to identify culprit.

If you look at all the facts, however, replacement windows are rarely the sustainable way to go. Here's why:

First, heat loss through windows actually represents a small (10 to 20 percent) portion of an average house's energy leaks. In fact, energy auditors say that drafts you think are coming from windows are often convective cooling from an uninsulated ceiling/roof. If you have a limited amount to spend, attic and wall insulation and sealing up major air leaks in the basement and ductwork should come before windows.

But 10 to 20 percent isn't nothing to your energy bill, and active drafts can really affect your comfort. If you're ready to do something about your windows, the first step is to understand what makes a window efficient or not.

Most of the heat lost through windows is lost through drafts—air leaks—not through the pane of glass itself. Some conductive heat loss happens through the glass and, at a different rate, through the non-glass frame.

Old wood windows can be repaired to seal as tightly as new ones, and if they were made before 1940, they are likely made with old-growth heartwood, which has a much higher insulating value than vinyl, aluminum, or even new wood. Replacement windows rely on their sealed double pane of glass for efficiency, lowering the conductive heat loss. But that double pane effect can also be gotten with a good storm window.

In fact, an old single-pane wood window in working order plus a good storm window has almost exactly the same R-value (about 1.8) as a new double-paned window.

And energy efficiency, as great as it is, isn't the only environmental factor to consider. Old wood windows can last for well over 100 years with proper maintenance. Replacement windows, on the other hand, only last 15 to 20 years, and they can't be repaired: if sealant around their double panes fails, the whole window has to be replaced. They are usually made from vinyl, a toxic substance to produce and dispose of. And every time a window is replaced, valuable building materials are sent to the landfill while new greenhouse gases and pollutants are release to produce the new window. It turns out that the old mantra of “reuse” applies to windows too!

Three Steps to Warm Windows
So if you're steering clear of window replacements, what do you do about your old, drafty windows? There are three major steps:

(1) Repair/restoration. Cold air leaks in your windows from cracked panes, disintegrating glazing (the putty that holdings the glass to the sash), cracks in the frame, or drafts where the window doesn't close properly. Whether you do spot repairs or a full professional restoration will depend on the condition of your windows, but it should leave you with a smoothly operating, well sealed, repainted window.

Erin Tobin of the New York State Preservation League points out that a full restoration will include allowing formerly painted-shut upper sashes window to open freely, adding energy savings in the summer by dramatically increasing cooling. Opening the top pane to allow hotter air to escape “makes a world of difference,” says Tobin; it allows her to avoid needing an air conditioner at all.

Many window repairs are easy enough for a DIY-inclined homeowner. Historic Homeworks sells a report with detailed instructions for every step of the way, or search for “wood windows” on the National Trust's website to get their tip sheet. If you're hiring a contractor, consider one with historic preservation experience, even if your home isn't in a historic district—they are more likely to think about the long-term lifecycle of your windows and not pressure you to replace instead. Contact your local historic preservation organization for a list of recommended contractors. Be aware that the process will be significantly slower than replacing windows.

A note on cost: As soon as you say “historic preservation,” many people will warn you that your costs are going to skyrocket. But in fact, most homeowners find that the costs of window restoration and decent-quality replacement windows are about the same; sometimes restoration is even more affordable. And that's not even counting the fact that it lasts so much longer. Bonus: Because more of the cost goes into labor rather than materials and corporate overhead, with restoration, you're also giving a larger boost to your local economy.

(2) Weatherstripping. There are three separate places to consider weatherstripping in a window. First there are the top and bottom, where there sash (the part that moves) meets the rail (or sill). You can get some effect from a cheap sticky-backed foam, but pros recommend a silicone/rubber gasket that will conform to the irregularities of your window. Second, there are the jambs, or the vertical surfaces that the window slides along. Pros recommend a strip of spring bronze that can be bent to the right angle to cover the gap. Finally, there's the place where the upper and lower sashes meet (known as the meeting rail). What you use here depends on how much of gap there is—more spring bronze might do it, or for bigger gaps two interlocking u-shaped metal pieces on the sides of the sash that meet can seal out drafts.

Since these are best installed when the window has been taken apart, it's a good idea to combine weatherstripping with repair and restoration work. Hardware stores will carry most of these types of weatherstripping, but a full range, along with new window hardware, can also be purchased at Architectural Resource Center.

(3) Get a storm window. Storm windows provide the effect of a double pane for a fraction of the cost. In fact, just adding a high-quality storm, without changing the existing window at all, has an energy savings payback time of only 4.5 years, compared to 40.5 for a regular replacement window, and 240 years for a low-e glass window. There are four major types of storm window:

  • Interior, acrylic panel, with a magnetic seal. Acrylic is a better insulator than glass and is lighter weight. With these systems, a homeowner installs a small steel track around the indoor side of the window frame, and a magnetic frame around the outside of an acrylic panel. It snaps in place with an air-tight seal. Kits for these kind of storm windows are sold by Magnetite and Window Savers.
  • Interior, “insulated panel.” A double layer of clear plastic film with cross-bracing, holding an insulating layer of air between them, in a plastic frame. Fits snugly into the indoor side of the window frame and is held in place with small hardware, essential giving you a triple pane. May not fit in all window frames. Sold by Advanced Energy Panels.
  • Exterior, triple-track aluminum. This has been the traditional storm window for decades, and they are easily available. Installed permanently on the outside of the window, they have a screen that can be lowered in the summer as the storm is lifted. If you have old ones that seem drafty themselves, it may be worth upgrading or at least resealing them.
  • Exterior, wood. The historically traditional storm window is enjoying a comeback both for durability and aesthetics. Using acrylic improves their insulating power and makes them lighter. They do have to be removed and reinstalled from the outside at the change of seasons. Local craftspeople, contractors, or handy homeowners can build them custom to each window, or they can be ordered from places like Green Wood Workshop. One manufacturer makes a traditional wooden frame with a “hidden” triple track storm window on the interior side, though this is much more costly than most storm window treatments.

Jennifer Quinn, who owns a historic house in downtown Albany, NY, recently had all her windows restored and added interior storms. She spent less on the restoration than she would have on replacements, and she's thrilled with the results: “They were leaking, rotting, some of them stuck, others wouldn't stay open. Now they all open with one hand and close with one hand. Now we know for sure we have no lead paint. We have no more drafts. And I know we're doing the right thing for the environment.”

A Note on Lead
Old windows are very likely to have lead paint on them. Before you have any window repairs done, educate yourself thoroughly about lead paint safety. Lead dust from renovations is a leading cause of lead poisoning. If you have lead paint in bad condition on your windows and children in the house, at a minimum you need to remove flaking paint and repaint. See HUD's for lead-paint safety guidelines.

Short Term Draft-Blockers
If you have drafty windows now, here are three quick things you can do before you get around to repairing them:

  • Lock them. Window locks force the windows tighter shut and reduce drafts significantly
  • Block them. Place a rolled up towel or leg of old pantyhose filled with rice on the sill, and also in the middle where the two sashes meet.
  • Cover them. Hang insulating blinds or drapes, and close them at night.

(A shorter version of this article appeared in Green America's Real Green newsletter in Winter 2009.)

Miriam Axel-Lute