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.

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.

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 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.

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.

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.

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.

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.