Repairing Your Home’s Original Windows for Curb Appeal and Energy Savings

Whether your house guests or potential home buyers, those standing at the curb and viewing your home for the first time will notice. Don’t think they won’t. I’m talking about your home’s windows. The following shows how repairing and thermally upgrading your existing traditional windows can maintain the curb appeal of your home and save money.

The visual character of most homes is largely defined by its windows, much like how eyes define faces. You may have seen medical illustrations where the identity of the subject is hidden by simply blocking out their eyes. Similarly, replacing your home’s windows, or blocking up window openings, can change your home’s character in both small and dramatic ways. There’s no getting around the fact that over time your home’s character is bound to change. But you may want to consider ways you can best manage this change. The purpose here is not to freeze your home in time in the name of historic preservation. We don’t live in house museums.

460 Bellerive Boulevard (built 1925) provides an outstanding example of well-maintained original wood windows.

To believe advertisers, replacing all your old windows with double- or triple-paned thermal windows can save you lots of money in heating and cooling costs. But here’s the big problem: the numbers rarely add up. An important 2012 study – Saving Windows, Saving Money: Evaluating the Energy Performance of Window Retrofit and Replacement  – quantified the costs and savings of different approaches in different American cities and climate zones. The study by the National Trust for Historic Preservation found that installing new high performance replacement windows would save an average of $555 annually in Chicago and $502 annually in Atlanta. But the average initial cost of replacing existing with all new high performance windows was about $34,000 in Chicago and $28,000 in Atlanta. Just to break even on such an investment would take 61 years in Chicago and 55 years in Atlanta. Real life experience bears out the findings of this study. Old house contractor Bob Yapp of Hannibal, Missouri, based on over 40 years’ experience revitalizing some 160 historic buildings, places the payback period at about 40 years for replacement residential windows and 150 years plus for commercial windows.

Saving Windows, Saving Money

Yes, you can buy cheaper double-paned windows, sometimes for as low as $200 apiece, but they will be of such poor quality that you’ll curse the day you installed them. The dirty secret of the replacement windows industry is that inexpensive vinyl windows will only last 12 to 15 years. Sadly, vinyl replacement windows are designed to be non-repairable and disposable. My wife and I once owned a Craftsman-era home in Champaign, Illinois which had half of its windows replaced with cheap vinyl. Within a few short years, most of these replacement windows were broken: panes cracked from the stress of opening; sashes nearly impossibly stuck shut; and failed seals between the panes, meaning that the gas meant to magically reduce heat loss leaked out and allowed condensation between the panes to obscure the glass. Meanwhile, our traditional wood windows still functioned well after a century, despite needing some repair.

Although advertisers will tell you that window sashes using double- or triple-paned glass are much more energy efficient than single-paned window sashes, most winter heat loss actually occurs around window sashes (by infiltration) and not through the glass (by conduction). For St. Louis’ climate zone, the U.S. Department of Energy recommends that the walls of newly constructed wood frame homes have a thermal resistance value – “R value” –  of at least R13 to R15. Compare that to the thermal resistance of single-pane window glass (R0.9) and double-paned windows with a quarter inch air gap (R1.72). Obviously window glass is meant to transmit light and air, not insulate against heat loss.

Instead, a more cost effective strategy is to stop air infiltration (drafts). In most cases you can drastically improve the energy efficiency and comfort of your home by making very cost effective improvements to your traditional windows.

Install Metal Weather Stripping. Nail long-lasting spring metal weather stripping around window and door frames to stop air infiltration. As opposed to plastic or foam, spring-bronze weather stripping will last a lifetime and cost about $15 per window. A few traditional hardware stores in St. Louis have recently carried it, such as Southside Hardware on Hampton Avenue.

Spring-bronze weather stripping nailed to the bottom rail of a wood window sash. Courtesy: Robert Myers

Better yet, use interlocking “rib strip” weather stripping. Although difficult to find locally

rib strip architecturalresourcecenterdotcom
Bronze “rib strip” weather stripping. Image via

this is an extremely effective way to stop infiltration of outside air. You’ll never go back to using plastic or foam weather stripping! You can either order through your local hardware store or search on the internet for “rib strip” weather stripping and purchase online.

The metal rib slides in a groove routed along the edges of the wood window sash and stops drafts. Image via
Hannibal, MO rib track weather strip
Zinc metal rib strip weather stripping. Courtesy: Belvedere Inn, Hannibal, Missouri.

Securing Loose Glass Panes. If the window glass is loose, remove and replace the window putty. (To remove the window sash you’ll first need to carefully pry off the window stops nailed vertically to the jamb.) Once the putty is removed, you’ll find that each glass pane is secured in the sash by small metal “points” which can be purchased at any hardware store. Use oil-based putty to reglaze the window glass as it will last much longer. Leave the putty exposed for a week to dry before priming and painting it. Once cured and painted, the putty should last for many years or even decades.

If glass replacement is necessary, consider whether using “safety glass” would look appropriate. The layer of plastic sandwiched between glass can provide a small thermal break which approaches the thermal qualities of double paned glass. An advantage of having no air gap is avoidance of the annoying condensation which invariably forms between double-paned glass once the seal fails.

Storm Windows. Installing good quality storm windows over your traditional windows is one of the top ways to improve their thermal performance and your comfort. Doing so will make your windows much more effective — often surprisingly close to the efficiency of a new double-paned window — and typically for a fraction of the cost of replacement windows. For both existing and newly installed storm windows, ensure that the seams around the top and sides are caulked tight. But leave some or all of the bottom seam, sitting on the window sill, non-caulked to allow a route for any condensation to “weep” outside or evaporate.

Traditional wood storm windows like this not only protect the windows themselves but improve your home’s thermal performance. Lacking operable sashes, this type of storm window was meant to be removed in the springtime and replaced in the fall. The prevalence of central heating and air conditioning now allows many to be left in place year round. Courtesy: Robert Myers

If you feel that installing storm windows compromise the look of your traditional windows from the street, consider installing interior window panels. The previously cited 2012 study found that installing interior window panels is one of the most efficient and cost effective ways to save energy and improve comfort.

casement window screen
Before purchasing new storm windows, first look for old ones in basements, attics, and garages (including garage rafters). The operable window screens for these casement windows were discovered in the home’s attic in excellent condition and wrapped in 1940’s newspaper. These screens could be retrofitted with removable plexi-glass panels and weather stripping to convert them to winter-time interior storm windows. Courtesy: Robert Myers

Draperies. Consider using multi-layered drapes as a way to control winter-time heat loss and air infiltration. The previously cited 2012 study found that installing insulating cellular shades actually provided the best return on investment for energy savings.

Repairing Wood Windows. Their ability to be repaired is one of the best qualities of traditional wood windows. Even badly deteriorated wood windows can be repaired by treating soft wood with wood hardener and replacing rotted wood with a two-part wood epoxy. Once shaped, sanded, and painted the repair will likely be invisible. A popular product for repairing deteriorated wood is Abatron ( but there are a number of others.

(Left photo) The corner of this window sash had rotted away but has been replaced by a two-part wood epoxy. (Right photo) Once shaped and sanded, this sash is ready to paint. The repair will then be invisible. Via

If you would like to become self-sufficient in windows restoration, you can attend a regional workshop led by nationally-recognized practitioners. You’ll also build self confidence and self reliance.

Belvedere School for Historic Preservation, Hannibal, Missouri.

International Preservation Studies Center, Mount Carroll, Illinois.

Window Preservation Alliance Events

Hiring a Professional. Thankfully St. Louis has numerous skilled contractors specializing in windows restoration and reproduction. An internet search for “St. Louis windows restoration” will lead you to a number of options. Missouri Preservation’s online Resource Directory — — also provides an extensive list of such contractors across the state.

Local contractors such as St. Louis Historic Window Company on Cherokee Street can not only repair old windows but build custom replacement windows appropriate to the building’s architectural character. Photo via

Window Replacement Strategies. Sometimes window replacement is unavoidable. To manage the cost and change in character of window replacement, consider using less expensive replacement windows where they can’t be seen from streets or alleys, such as on the sides or rear of your home. Doing so will help to maintain the character-defining views of your home.

bad replacement windows
To maintain curb appeal, any inexpensive replacement windows should be installed where they can’t be seen by the public. Courtesy: Robert Myers

And when blocking in a window opening is absolutely necessary, a cost effective alternative is to permanently install window blinds in the window opening so that it simply appears that the blinds are closed. Doing so will help maintain the character-defining pattern of window/door openings to wall space. Instead of blocking up a window opening for privacy, such as when adding a bathroom, the solution can be as easy as replacing transparent window glass with obscured glass.

Guidance. For guidance on the repair and thermal upgrade of windows, you can consult the U.S. National Park Service’s Preservation Briefs: (for wood windows) and (for steel windows).

In summary, repairing and thermally upgrading your existing traditional windows can maintain the curb appeal of your home and save money.