Restoring vs. replacing historic windows - data?


Perhaps the most frequent and bitter of debates I see between historic preservationists and the average resident of an older home is window replacement. From the preservationist's standpoint, original windows are among the most important of defining characteristics of historic residential architecture. The typical rejoinder from the homeowner, convinced that replacing old drafty windows is key to home energy savings, is, "Okay, but are you going to pay my heating bills?"

The preservationist, in turn, will assert variously that significant energy savings can be achieved by properly restoring and weatherstripping the existing windows; that the return on investment from replacement windows vs. repair and weatherstripping is too low for replacement to be financially worthwhile; and, showing some savvy when dealing with purely environmentalist criticisms, that the embedded energy that goes into a replacement window is far greater than the lifetime savings of the replacement, and that the R-value of even a high-end energy efficient window is still very low.

But none of these assertions are very convincing to me, because they're just that - assertions, without any sort of empirical backing presented. And if I'm left somewhat cold (so to speak) by these data-free assertions, just think of the homeowner upset with his heating bills. One would think preservationists would have a strong interest in providing historic building owners that restoring their existing windows is a better investment than replacing them - changing an adversarial encounter into a cooperative one.

So far, though, even JSTOR has failed me in my search for empirical data. The only thing I've found so far (through Google) is a 1997 article from Home Energy Magazine, Creating windows of energy-saving opportunity. This study of the windows in 30 Vermont buildings, some unrestored, some restored, some replaced, entitles its conclusions section, "Preservationists take heart".

Our study of old windows showed that the energy savings are similar for a variety of retrofit and replacement strategies. Rates of return on investment for energy improvements are quite low when starting with typical or tight windows with storms in place, but are significantly higher when renovating loose windows with no storm.

The difference in annual energy savings between renovating an old sash and replacing it with a new one was very small--retrofits saved only a few dollars.

For preservations, the good news is that with a proper choice of renovation strategy and good workmanship, historic sashes can be almost as energy-efficient as replacements.

This is still not as thorough an article as I would like - as low-hanging fruit, costs of various options are shown in a table, and annual savings are discussed, but those numbers are nowhere combined to provide a direct comparison of ROI - all it would have taken was another column in an existing table.

Is anyone (Dale and Joe, I'm looking at you) aware of other empirical articles on historic window restoration versus replacement that provide clear evidence that restoration is a financially better option?

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All parts of the window

In my experience, a lot of historic windows had less historic storms or screens added at some point. The arguments for keeping a lovely seven- or twelve-pane window from the 1910s or 1920s seem weaker when the storms are a tinny aluminum contraption from the 1950s or 1960s. That does however bring up the point that, sometimes, it's not the window that needs replacing but the storms.

Our apartment had its original (ca. 1910) windows when we moved in. After a $445 heating bill one exceptionally cold January, our landlord offered to replace the windows and we took him up on it. One thing that struck me during the replacement was how much actually needed replacing. The window frames themselves were loose--you could for example see daylight through a gap where the vertical divider between two windows met the sill! The old windows were counterweighted, as so many old ones are. The pockets inside the frames that held the counterweights were drafty. Thus replacing the windows also involved stuffing the now-useless pockets with insulation and re-caulking the window frames.

I think that any serious comparison of restoring versus replacing old windows should also factor in the differential costs and effort of repairing the frames. Since we were replacing the windows, it was just a matter of sealing up areas that we no longer needed. If we had been restoring the windows, obviously, we couldn't just fill and caulk the frames. Those repairs would certainly have cost more. How much more, I don't know.

old window repair

Lots of stuff on the web ...

Casements ... Article by Peter Clement

Preservation Brief #13/Thermal Upgrading of Historic Windows ... National Parks/Technical Preservation Services Guides

Try these on. Locating suppliers/contractors is the real trick. As for dollar
comparisons, it's tough. So many aspects of an old window can go wrong and frustrate an owner into wanting to replace rather than repair. Glazing, weatherizing and putting up the storms is what needs to be done for energy savings. Also, inside thee wall ... if the outside was not sealed/caulked at installation and/or the window framing has issues, those issues need to be addressed ... air leaks have to be fixed.

Interior storms full or partial can be made quite handsomely for windows an owner does not want covered up on the outside, such as steel casements.

All of these alternatives are cheaper than buying a quality new construction full window. Even muntins and mullions can be repair, epoxyed and painted.

... for atarters.


I see in those links arguments similar to what I'm trying to avoid. "Rehabilitation can be just as effective as replacement, and also cheaper - but no, we don't have any data. Just trust us." From the Preservation Brief,

The ease with which they can be replaced and the mistaken assumption that they cannot be made energy efficient except at great expense are factors that typically lead to the decision to remove them.

In many cases, however, repair and retrofit of the historic windows are more economical than wholesale replacement,

But where is that assertion backed up? If somebody's coming in with the attitude that historic windows are expensive, and nothing can be done to change that, simply telling them, "Oh, no, they can be repaired good as new!" isn't very convincing. I'm trying to find a way to state the point in a fashion that will make people say, "Oh, hey, that's really interesting, thanks!" instead of walking away grumbling, "Yeah, sure, whatever - you're not the one paying the heating bills."

Again, the preservation brief contains - but only in a footnote - the beginnings of a good argument:

One measure of energy efficiency is the U-value (the number of BTUs per hour transferred through a square foot of material). The lower the U-value, the better the performance. According to ASHRAE HANDBOOK 1977 Fundamentals, the U-value of historic rolled steel sash with single glazing is 1.3. Adding storm windows to the existing units or reglazing with 5/8" insulating glass produces a U-value of .69. These methods of weatherizing historic steel windows compare favorably with rolled steel replacement alternatives: with factory installed 1" insulating glass (.67 U-value); with added thermal break construction and factory finish coatings (.62 U-value).

Combining this with some data on the costs of these various options, and the heat transfer expected over a year, and putting a reference to this number right up at the beginning of the article is what I'd want to see.

It doesn't have to be exact - "In your particular case, repair will be 63% more cost-effective than replacement," - but can be more generalized, "Rehabilitation of rolled-steel windows can achieve nearly the same energy efficiency as replacement, and is typically 30-80% more cost-effective." Alternately, case studies of various starting conditions can be used to calculate the cost and benefit of each option, and show how rehabilitation can be more cost-effective than replacement.

Yes, these things are thought-intensive. However, if the goal is to preserve historic material, I think that putting effort into providing educational carrots can only be a good thing. It's the soundbites that win the hearts and minds - handing people a long preservation brief on *how* to rehab their windows without providing them with the information they're concerned with, cost, is not nearly as effective as having your viewpoint represented in the newspaper. As I note in the original post, "Everybody knows" you should replace your old windows for hassle-free energy efficiency. Just because a belief is wrong doesn't mean it's not influential.

The problem is

historic preservation does not have the research history or infrastructure that it should. I've noted that this is partly due to preservationists' emotional commitment to the past rather than a rational consideration of the future. If you ask me, there is a HUGE gap/opportunity for this type of research now.

There were a few studies and experiments on preservation and energy efficiency in the 70s, but there is not much since then.

A couple of cites you might check out if you've got the time (neither carried by U-M):

Energy ratings of domestic windows. Research Focus , no. 41, pp. 8. May 2000.
(British Civil Engineering Journal)

Selecting Energy Efficient Building Envelope Retrofits to Existing Department of Defense Building Using Value Focused Thinking by Pratt, David M.
(DoD report)

These came from the CSA Engineering Research Database and Avery Architecture Database. I don't know if JSTOR indexes the type of journals this kind of research would appear in.

studies from the '70s

The few empirically-oriented references I could find did seem to be from the 1970s, which makes sense, considering both the relative energy of the environmental movement at the time and the energy shocks. But I considered these references not terribly useful for current purposes - good for explaining to people why vinyl inserts from Wallside weren't going to do much good, yes, but somebody who has been looking at triple-glazed, ultra-mega-techno-coated Pellas or Jeld-wens at Fingerle or Chelsea Lumber isn't going to be at all convinced by 30-year-old data on vinyl inserts.

As you note, though, I think there's a clear and present opportunity for preservationists here: from both environmental and financial points of view, energy efficiency is a hot topic, and there's a lot of support for efficiency research.

I see that same opportunity as a fairly present danger, though - the Federal government will pay back 10% of the cost of new (replacement) Energy Star certified doors and windows, and support is building from there for even more government action to promote efficiency. While putting some timely empirical research behind the "historic preservation is green building," mantra could help build support for restoration and rehab of historic buildings, I think the continuing absence of such data could threaten preservation efforts.

I can imagine a point when the fervor over energy efficiency reaches the point that legislation is passed prohibiting local historic district commissions from preventing the replacement of windows with new Energy Star certified windows. This possibility alone ought to provide sufficient impetus for getting behind empirical research - nothing like having your hard-fought legislative victories negated by somebody else's hard-fought legislative victories, especially if the sad irony of the situation is that your position could have instead been strengthened by their efforts if only you had the data! The current focus on green building present an excellent "yes, and" opportunity for preservation.

...But that's not to say this is on my ever-in-flux list of "things to do a phd on". I'll consider this discussion my gift to some student actually in the field.

If someone really does want

If someone really does want to do a PhD on this topic, they better start collecting data ASAP. Gathering sufficient data points to produce reasonable confidence intervals takes a while.

...Of course, if you were doing this as a for-reals project, you need not limit yourself to once-monthly readings. You could use daily meter reads and temperature data. You'd still probably need two full winter periods, though, to give some idea of the performance over the full local temperature variation.

The trickier issues is, how many houses would you use? You wouldn't use one, obviously, because who's going to restore their old windows and then replace them? That militates at least two houses, but then you have the problem of all the "house fixed effects," in the lingo. However, if you took a sample of houses with old windows and then randomly assigned them to treatment (restoration versus replacement), you could probably begin to zero in on the average treatment effect.

Repair v. Replace $$

Start with some recent local projects using numbers provided by local preservation contractors.

My 1930s 5-bay, 20'x40' garage job in the Woodbridge area of Detroit, for instance. The demolition (my budget figures are with my client), haul-away, landscape repair and a new 8-foot stained fence along the alley, plus some langscaping, approached $18,000. (Not my estimate.)

I proposed a straightening to as close to square as possible, a reinforcing of the stud walls and tieing in the collar beams to the roof joists (an old Amish trick), and lastly a repair of two(of the three) bay doors that hung on roller tracks to make the alley access functional and secure, the "permanent-for-the- moment" securing of the other three bay doors, repair of the garden side man door, plus some general "foam" weatherizing of the siding leaks from the inside.

My estimated flat fee for these steps was $8000 plus materials. The final fee came to $12,000 and change; and took two months (waiting for the garage to move, primarily).

The client then asked me to repair the lower 4' of deteriorated exterior clapboard in addition. The fee for removal of the old and irreplaceable (double reval 5/8" fir) siding was $4000 time and materials.

The siding that could be saved was trimed and used to replace siding on the garden side, which was not part of the job, but was appreciated. The bottom of the two sides was recovered using treated plywood underlayment, Tyvek moisture barrier and a deliberately wider reveal primed grey hardiplank. An aluminum "Z" strip was added at the "break" between the old material and the new to help shed rain. The new area was painted with the same exterior paint.

Versus loss of the entire structure, there was a savings. And she saved an historic garage, which is now accessible, and preserved a view from thee rear of her home that otherwise would have been an inner city alley.

And she got more done and still saved $2000.

Other contractors can tell other stories. I have more, as well.

But this client would have spent even more ... because she wanted to save the garage. Like myself, preservation requires some personal commitment.

I believe it is a FACT that repairs are the way to go ... but by the same token, it DOES sound lame without the facts/stats/stories to back it up.

Purely anecdotal

This is purely anecdotal, but my parents' house dates from the late 1890s/early 1900s, and had the original windows (with the obligatory circa 1960s through 1990s storm windows- they were added and replaced in stages) until one or two years ago. The old windows were well-maintained, well-restored, well-weatherstripped, and had a lot of the joints/airspace filled with that Great Stuff! stuff, to the best of my parents' This Old House/Victorian Home Magazine/etc knowledge and ability (which is better than many contractors out there, at this point), and they *still* noticed a significant increase in energy efficiency when they installed new windows in the upper story of the house. They didn't even install top-of-the-line windows, if I remember correctly. They were just a Lowe's special, I think- probably not an Armstrong or Pella-level brand.

a significant increase - of what value?

The important part of the equation, I think, is just how much the efficiency increase is. It's quite possible that replacement windows can net a noticeable increase in efficiency, but still not be *worth* it, if the increase isn't enough to overcome the initial investment. I support projecting energy cost increases at a significantly higher rate than inflation when calculating cost/benefit, but I still want to see that calculation made.

Monetarily speaking...

I think they said the windows would have paid for themselves within five years. Of course, for the Truly Green argument, that's just a payoff of the purchase price, not the externalities involved in the manufacturing of the new windows or the disposal of the old. I'm going to go out on a limb and say that they didn't calculate those.

I also don't think that they got fancy with the calculations- didn't factor in inflation, didn't factor in fluctuation in energy rates, etc etc. They *probably* just did a back of the napkin "we saved this much this year, this is how much we paid for the windows, if we see similar savings each year" calculation, which is what the Average Joe would do.

Wow, that's pretty good.

Wow, that's pretty good.

Considering how high fuel

Considering how high fuel costs are where I am saving money even in the long run is an option we've taken, having new double glazed windows installed and then sealed properly, better insulation through out as well as the ceiling and more important the basement the foundation picks up so much cold in the winter it spreads through the walls and entire house. I think a lot of people over look the fact that you can and should insulate your basement ceiling.


Bonnie, I have many questions in response to your posting "Purely anecdotal." How do you define well-maintained, well-restored windows? To restore a window-it takes much more than filling in glazing compound where it is missing and applying a coat of paint. Were the sash stops ever restored or repaired or replaced? Were the storm windows a triple track system?-I ask this because the older storms (when maintained) are more energy efficient than the triple track system. Did they replace the windows in kind and/or wood, or are the replacements vinyl with flat muntins? The average cost to replace a window is from $350.00 and up, pending on the window/s chosen, installation, and most commonly trim work (exterior & interior). I can restore an old window to a R-value or better for $350.00 and under (depending on the condition). The materials that were used to build older homes (60+ years old) are of better quality than most homes built today. Slate roofs, redstone foundations, harder woods and so forth. These materials have stood the test of time and continue to do so in many homes, therefore it is better to preserve, restore and repair, than it is to replace. Yet, if one NEEDS to replace, it is best to replace in kind.

more clarifications


I have a few questions about your post. I realize this is probably a dead horse since you posted almost a year ago, but...
What r-value or better are you able to restore an old window too, I ask because all you say is 'I can restore and old window to a R-value or better for $350 and under..." you never actually give a value?

February last I went before a board to argue my case for window replacement based on many conditions but mostly on increased energy efficiency. Turns out most of my 36 page report was null since the board will not accept arguments against storms since they are considered a 'temporary' installation.

Regardless, after a four month search, the only data I could find rating a single pane window with storm came from the 1985 ASHRAE fundamentals handbook (note: over two decades old). It was given a u-value rating of .5, (or r-value of 2 if you like). Today's insulated double pane windows achieve a u-value of the low .3's (r-value of 3) or almost 1 1/2 times better than a single pane window with storm applied.
Now reality forces us to think about this .5 rating. In 1985 they weren't making weight and pulley windows so the ASHRAE probably isn't going to build a window system that the public couldn't buy.
Chances are they went out bought (no longer represents a restored window) a single pane window - probably a brosco which was in a vinyl track (no longer represents a weight and pulley window)- applied a storm window to it and tested it.
I called the ASHRAE archive department, they have no data speaking to which window system was tested, as such - according to the ASHRAE - it was a theoretical calculation which according to the ASHRAE themselves, shouldn't be used for real world comparisons or calculations. So since absolutely no data exists proving the inefficiency of a restored weight and pulley single pane window with storm applied, it actually could be the most efficient window system on the market right?
I then contacted the NFRC asking them for a rating of a restored weight and pulley single pane window with a storm applied. The NFRC will actually not test a restored or new weight and pulley single pane window because there are simply too many variables making a consistent energy performance difficult to predict and impossible to duplicate.
I then contacted one final person, the most consistent, scientific report I found came from Oak Ridge National Laboratories in an article named "To Storm or Not to Storm: A measurement Method to Quantify the Impact of Exterior Envelope Air Tightness on Energy Usage Prior to Construction." by Andre Dejarlais. Andre told me without a doubt in his professional opinion no single pane window with storm will ever outperform an insulated double pane window and 'the data will prove this'.

Additionally, I'm interested in your $350 restoration number? Did you factor in rope replacement, reglazing, oiling, sanding, adjustment of the stops and repainting? Because that number seems a little low, what is your hourly rate?
I figured around $500 / window - 5 hours per window for a carpenter @ $35/hr
1 hour rope replacement
2 hours glazing the window (technically a painter would do this but its easier this way)
1 hour sanding and oiling
1 hour for stop adjustments (wood moves season to season)
Now because of the sanding and reglazing the window needs to be repainted that's $300 per window or $150 per side.
Total around $475 + materials. This doesn't include the installation of a new storm either (figure $200), or 5 year maintenance which hopefully will be less and is absolutely necessary, wasted money on energy costs, wasted money on an obsolete technology and an increased carbon footprint. New windows have recycled aluminum exteriors, recycled composites (they aren't really vinyl anymore)and wood from sustainable forests. Not because they care but because its cost effective for them.
If you want to talk about environmental damage lets talk about all that lead paint on your old windows and how every time you open and close them little pieces are ground off and become airborne. Years of over painting the sash and the stop and the fact they rely on friction to keep them weather tight. I'm not even going to talk about all the coal dust stirred up by those weight pockets either.

I'm going to stop here - shame because I didn't get to talk about air infiltration, remember conduction, convection and radiation, and the fact that new windows are at least 3 times better (worst case scenario) at keeping wind out than old ones. Keep in mind that a 1/8" gap around a door is equal to a 2" hole in your wall. A 3'x7' door has a 20' perimeter. A 3'x5' double hung window has a 19' perimeter at this point its easy to do the math.

I'm happy to discuss any of this, and I'm not a window salesman either.

window efficiency studies

Trevor -

Thanks for the investigation - sorry I didn't check my comments queue and get it approved sooner.

Do you have citations for the ASHRAE and Dejarlais studies?

Old House Journal on windows

Yesterday, I was shown a dead-tree Old House Journal bit on window replacement, with a graphic showing relative payback rates of various window "improvements". The graphic showed cost of the improvement, BTUs saved, annual value of energy savings, and payback period - removing a historic window in good condition with a tight-fitting storm window and installing a new double-paned, low-e window came up with a payback period of 240 years, or "definitely not worth it".

Alas, the online article doesn't contain this graphic, and, additionally alas, there wasn't any methodology section accompanying the graphic. The text of the article was the standard hollow assertion of, "Sure, they probably need a tune up, but when rehabilitated, traditional windows and doors can offer energy benefits comparable to new replacements."

The latest issue of

The latest issue of Earthwise (the newsletter of the Union of Concerned Scientists) includes a profile of Wes Foell, a professor at Wisconsin-Madison. It discusses his 37-year efforts to retrofit his Prairie-style house (with lots of windows, yo!), and his "35-year quest to track and optimize energy use throughout the house....With each of his many home improvement projects, Wes has considered the initial financial investment and its payback time to determine which upgrades will give him the 'biggest bang for his bucks.' Wes began by calculating the heat loss from all exterior house surfaces in order to prioritize potential improvement projects..."

Anyway, he might be good source for methods.

cost vs value

Another thing you might want to keep in mind in this argument is value of the home. While over the life of the home the energy savings are probably going to add up to a whole lot more money, you are also affecting how much the property itself is worth by choosing to have one kind of windows or another. Depending on the style of the home and the prevalent style in the neighborhood I think this could have a significant impact on what you'd be able to sell your house for.

Unfortunately as far as scientific rigor goes, you'd be right out of luck there, I think. As far as I can tell house appraisals can vary pretty wildly, so you'd need an unfeasibly large sample in order to capture "average" trends (which might still not apply to _your_ home depending on the circumstances).

Still, it's something I'd try to keep in the back of my mind as a secondary or tertiary consideration (after efficiency and what you actually like getting up to look at in the morning).

property value

House appraisals do vary pretty significantly - in no small part because the typical appraiser working for your mortgage company looks at a mere handful of "comparables", and is only trying to find something like, "is it in the ballpark of, or greater than, the mortgage you're asking for?" Your local Assessor and County Equalizer use much larger datasets and can get things a little more accurate, and Zillow has a larger dataset still - though even these larger sets suffer from a pretty large degree of missing information. (Zillow's estimated price range on my house is "$109k - $149k", a pretty huge window, and that's even after I gave it a lot of additional info.)

Though you're right as to neighborhood norms / prevalent style, which points to one justification for regulated historic districts, even in absence of absolute information about price/return. I'll set aside questions here and assume here that historic preservation has value (to the community and to neighbors of a preserved home), but that value is not immediately apparent to the typical homebuyer. If a home's value is partially determined by its conformance to neighborhood norms, then an appropriately renovated home is going to be penalized in valuation relative to its neighbors that have been inappropriately changed - people will say, "well, clearly, this home is the oddball that hasn't been 'updated' the way its neighbors have," and will value it less. If all the homes share the same traits, such as wood windows that haven't been replaced with vinyl, it levels the playing field. Immediately visible changes that have been well-marketed as valuable, such as replacement windows, now longer overshadow the less readily apparent qualities of the home, such as "faithful to its architectural style".