If you’re trying to lower your energy bills, you have probably plugged many of your home’s air leaks and have added insulation to your attic floor. Now you may be wondering, “What should we do about our old windows?”
Unfortunately, there is no clear answer to this question. Sometimes it makes sense to leave old windows exactly the way they are. Sometimes it makes sense to repair the windows’ weatherstripping and add storm windows. And sometimes it makes sense to replace old windows with new energy-efficient windows.
Before providing a framework to help you decide what to do, it’s important to address a few basic questions about window replacement.
Will new windows save energy?
Here’s the good news: if you install new energy-efficient windows, your energy bills will go down.
Here’s the bad news: your bills won’t go down as much as the window salesman promised. In fact, your new replacement windows will save you so little money on your energy bills that the payback period for this investment may be more than 100 years — far longer than the new windows are likely to last.
Of all the data-crunchers who have looked closely at energy savings attributable to window replacement, none are more credible than Michael Blasnik, a Boston-based energy consultant with access to utility bill data for millions of U.S. homes. “I’ve looked at a lot of window replacement data,” Blasnik explained at the Building Energy 12 conference in Boston. “I’ve heard window salespeople say that you can save 50% on your heating bills if you replace all your windows. In fact, the amount of energy saved by replacing all of the windows in a home is generally on the order of 1% to 4% of the heating energy usage.”
Exaggerated marketing claims by companies selling replacement windows have exasperated energy experts for decades. “Window replacement has a 200 to 300 year payback period,” said Blasnik. “A Wisconsin study found that a lot of the expected energy saving is lost by the reduction of solar gain. Most replacement windows have low-solar-gain glazing, so maybe half the energy saving is gone due to the reduction in solar gain. I tell people, go ahead and replace your windows if you want, but don’t expect significant energy savings.”
In short, says Blasnik, “the measure is not cost-effective.”
What if I leave them just the way they are?
While many older homes still have their original single-glazed windows, almost all such homes (especially those in cold climates) have had triple-track storms installed by now.
Single-glazed windows with exterior triple-track storm windows don’t perform quite as well as new double-glazed windows, but their performance is surprisingly close. The annual difference in energy bills may amount to just $1 or $2 per window.
Before embarking on an expensive plan to fix or replace your windows, ask yourself three questions:
If the answer to all three questions is “yes,” you may not need to do anything at all.
What about lead paint?
If your family includes children under the age of 6, or anyone who may be getting pregnant soon, and your house was built before 1978, you need to determine whether your existing windows have lead paint.
You can test the existing paint with a do-it-yourself test kit or you can hire an abatement company to test your paint. If your windows have lead paint, and your family includes vulnerable members, you should consider lead abatement work or window replacement by a contractor familiar with lead-safe practices.
To learn more about these issues, visit:
- The EPA web page on lead hazards
- The HUD web page on lead hazards: “About Lead-Based Paint”
- The New York State Department of Health web page on lead hazards: “What Homeowners Need to Know About Removing Lead-Based Paint”
OK — I want to fix up my windows
Let’s assume that your windows don’t include any lead paint. If you want to improve the energy performance of your windows, it’s fine to do so. Just don’t expect that you will save enough energy to justify your investment.
If you’ve decided to invest in improvements, you have two choices: repair or replace.
Why would you decide to repair old windows instead of replacing them? There are several possible reasons:
- You value the look of your historic windows, and you want to preserve them.
- You are worried that new windows won’t last as long as restored historic windows.
- You care more about the character of the house than achieving the lowest energy bills on the block.
- Your house is located in a neighborhood controlled by a historic preservation commission.
When this topic has come up on GBA, many readers have posted cogent arguments in favor of repairing historic windows. For example, here’s what James Morgan, a designer in Carrboro, North Carolina, has to say: “The laws of physics, when consulted on the big energy picture, tell us that for a historic building (with usually rather limited fenestration), glazing U-factors are a relatively minor consideration compared to all the other usual energy retrofit suspects.”
The authors of an oft-cited 1996 study (“Testing the Energy Performance of Wood Windows in Cold Climates”) concluded, “Replacing an historic window does not necessarily result in greater energy savings than upgrading that same window. The decision to renovate or replace a window should not be based solely on energy considerations, as the differences in estimated first year savings between the upgrade options are small.”
How can I repair my old windows?
Repairing an older window can easily cost as much as replacing it — or more, if the work includes certified lead abatement.
According to a Fine Homebuilding article, “Should Your Old Wood Windows Be Saved?”, repairing old windows is usually cheaper than replacement. “Restoring and upgrading old windows isn’t cheap, but much of the expense is paid in sweat if you’re willing to do the work yourself… According to [window specialist Jade] Mortimer, a professional may charge around $200 for a complete restoration and upgrade of each window — maybe more, depending on the damage. However, if you do the work yourself, you can generally expect to pay less than $100 for materials. A storm window can cost as little as $80 or in excess of $300. Again, the upgrade can cost much less if you build your own.”
In most cases, repairing an older double-hung window will require removal of the interior stops and parting beads; inspection and repair of the sash weights, sash cords, and pulleys; installation of new weatherstripping and (in some cases) sash locks; repair of the window putty; and new paint. For more information on this work, see two useful Fine Homebuilding articles:
Window shades and window quilts
If you want to improve the energy performance of existing windows, and you don’t care about cost-effectiveness, you might want to install interior insulating shades or window quilts.
For these devices to save energy, you have to remember to pull down the shades or window quilts in the evening, and open them in the morning. (During the winter, if you forget to open them during the daytime, you might miss out on desirable solar gain.) Some homeowners don’t mind these tasks; others hate them.
According to GBA technical director Peter Yost, “Field testing indicates that insulated cellular shades with sealing sidetracks contribute about R-4 to the window. … We have just installed such shades in our home and I have to admit some winter nights go by with more than one shade stacked in its stored position with an R-value of about 0; and optimally deploying the shades on cloudy versus sunny cold winter days is more than a bit challenging, even for us folks with home offices.”
For more information on insulating window shades, see “Insulating Window Shades” by Marc Rosenbaum.
Low-e storm windows
If your older single-pane windows already have storm windows, it makes sense to keep the storms you have. Of course, storm windows are only effective if they are closed during the winter. (A surprisingly high percentage of triple-track storm windows are left open all winter long.)
If you live in a cold climate, and your windows don’t have storms, it makes sense to install low-e storm windows.
There are two basic types of low-e coating: sputtered (also called soft-coat) and pyrolitic (also called hard-coat). While either type of low-e coating is suitable for use in a sealed insulated glazing unit, only pyrolitic coatings are hard and durable enough for storm windows. When used on a storm window, the low-e coating faces the interior. Since most pyrolitic coatings have a higher solar heat gain coefficient than most sputtered coatings, pyrolitic coatings are particularly appropriate for cold climates.
Research has shown that an old single-glazed window fitted with a low-e storm window performs as well as a new double-glazed low-e window. According to a classic 2007 study by Craig Drumheller, the average payback period associated with the installation of new low-e storm windows on older homes in Chicago was 4.3 years.
If you are intrigued by low-e storm windows, there is a caveat: this type of storm window works well when installed over single-glazed windows, but should never be installed over newer double-glazed low-e windows. According to an article in Environmental Building News, “Modeling performed for LBNL by sustainability consultant Thomas Culp, Ph.D. has uncovered the potential for serious overheating problems when low-e storms are added to low-e windows: in hot weather, in direct sunlight, temperatures up to 185° F (85° C) may be reached. That kind of heat can cause premature aging or failure of the insulated glazing unit’s seals.”
Hot climate concerns
Old single-glazed windows are, by definition, high-solar-gain windows. On a sunny winter day, that’s good news. However, on a hot summer day, it’s bad news — especially if the windows face west.
If you live in a hot climate, you probably worry more about your cooling costs than your heating costs. Solar gain through windows is a major factor affecting cooling loads, so it makes sense to address solar gain in rooms that overheat.
Excess solar gain can be addressed by providing improved shading (for example, with a trellis or an awning) or by installing solar control window films. For more information on window films, see Window Film: An Overlooked Retrofit Option?
Another (expensive) option is to install replacement windows with low-solar-gain glazing.
New replacement windows
It sometimes makes sense to install new replacement windows in an older home — as long as you realize that you’ll never see enough savings in your energy bills to justify the high cost of the work.
One fan of window replacement is GBA reader Keith Gustafson. According to Gustafson, it usually makes more sense to replace older windows rather than attempt to repair them.
“In my opinion the only way to get an antique window to be at least partly airtight involves removing it from the building, since it was never sealed or intended to be sealed originally,” Gustafson wrote. “In doing so you will doubtless find that some pieces are beyond their practical life — in other words, rotten — and need extensive rebuilding.
“It is also my opinion that whatever strategy you use for sealing the sashes to the frame is to some extent temporary. Wood moves grows shrinks and shifts and those sashes were never intended to be airtight and will continue to leak air to some extent, and this will grow over time, especially if they are used regularly. There are good companies that make these weatherstrip products but they are very dependent on the quality of install and if you are paying for the labor it is going to add up.
“Once this is done, you have the honor of maintaining via paint and putty on a regular and ongoing basis. I have watched panes fall out of their sashes behind storm windows. While storm windows are less expensive than new windows they are still real money, a quick search finds a decent looking triple track with screen for 150 bucks, while The Despot has them down to $60. None of these are airtight or low-e. The Despot will also sell you an Andersen 400 series for less than 400 bucks, or a vinyl window for less than 200 bucks. (All the prices are for around a 3 foot by 4 1/2 foot window.)
“It would surprise me if the actual bill for properly refitting antique windows and adding a good quality storm window was actually significantly lower than the cost of installing a decent quality replacement window. If you are doing the labor yourself, then you will be cheaper since you are free, but people hereabouts who are worth hiring run $25 to $50 an hour, and that adds up in a hurry.
“If you love the look of antique windows (which actually I happen to) or are legally required to save them, then this sounds sensible. Take none of this to mean that you should buy a house full of windows from the guy with bad breath, a lime-green polyester sport jacket, and the magnetic sign on his truck. Restoring old windows is a labor of love, or the product of intense hatred of vinyl windows, but I think both long and short term it is not a big financial gain.”
Pay attention to flashing and egress issues
If you decide to install new replacement windows, choose a reputable contractor to perform the work. It should go without saying that the contractor should have a good understanding of moisture management issues and methods for flashing rough openings. Unfortunately, not all window replacement contractors fall into this category.
Remember, building codes appropriately require every bedroom to have at least one window that is large enough to provide egress in an emergency. It’s important to verify that your window replacement contractor understands this part of the building code. A bedroom window with a small rough opening may require a casement rather than a double-hung to meet egress requirements.
Comfort is worth paying for
What’s the bottom line? If you live in a cold climate, and your house has older single-pane windows and no storms, you should invest in low-e storm windows. If you live in a hot climate, you may want to invest in window film to reduce solar gain.
It’s hard to justify any other improvements to existing windows on the basis of energy savings. That said, many people want to repair or replace older windows for other reasons. If your older windows are drafty, or if you skin feels cold when you sit beside a window on a winter night, you may be happy to spend $400 or $500 per window for improved comfort.
Martin Holladay’s previous blog: “The 2012 Code Encourages Risky Wall Strategies.”