Jim, I'm going to refuse to give up so easily.  I excerpt below from The Economics of Historic Preservation (National Trust for Historic Preservation, 1994) by Donovan Rypkema, p. 94, issue number 90:

Real estate is an asset that typically has a long physical and economic life.  It is certainly unfortunate, then, that all too often the standards of measurement for economic return on real estate are short-term criteria.  Private-sector owners ought to measure life-cycle costs, almost none do.  Public sector owners certainly should concern themselves with a long-term cost horizon; few do.  Once again, the Department of Defense is a surprise exception to this public- and private-sector myopia.

"Components of a building, such as historic windows and doors, although traditionally not designed with energy conservation in mind, can be retrofitted to meet current statndards of energy use.  This can be achieved at less immediate and long-term cost than replacement units, while preserving significant historic fabric.  In fact, studies have shown that the replacement of historic wood or metal single-glazed windows with contemporary units, such as vinyl or aluminum double-glazed sash, cannot be justified on the basis of life-cycle costs.  DoD and other Federal agencies have discovered that preservation of these components meets mission requirements at a lower cost to the government."

The Benefits of Cultural Resource Conservation: Commander's Guide  
Prepared by CEHP Incorporated and John Cullinane Associates for the Department of Defense, 1994

Add to this the maintenance expense in 15 years when the seals in these enormous thermopane units begin to dry out, the vacuum is lost and they begin to fog.  Now you get to replace the sash again.  Just rehab the existing sash and install narrow-profile baked-on enamel finish aluminum storm windows. The storms will take all the weather so you won't have to paint and replace glazing compound nearly as frequently, and the storms are a removable feature should anyone wish to restore the original appearance.  Infiltration will be reduced to nil, especially if you weatherstrip the sash channels as well.  Instead of sending your money out of the local economy to a window manufacturer in Upper-Slobovia, keep it in town to pay a local craftsperson to lovingly maintain the sash.  They'll come to your store and buy a loaf of bread later, AND splurge on that expensive jar of preserves to spread on it because they had the good fortune to land that window contract and they have some discretionary spending money.
____________________________________

Dan Becker, Exec. Dir., RHDC
Raleigh Historic Districts Commission
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-----Original Message-----
From:   Jrhodes [SMTP:[log in to unmask]]
Sent:   December 11, 1998 9:28 AM
To:     [log in to unmask]
Subject:        Replacement (!) windows

Greetings! (My first pinhead inquiry)
My home village, a suburb of New York City, has ruled out consolidation
(sorry Mr. Stahl) of the wood windows on its not-so-historic 1920's brick
Municipal Building.  They still want to preserve the appearance of its
average 3'-4"W x 9'-4"H D.H. windows, each sash 9 over 9, (up to twice that
width with fan head) windows.  Thermal rating (insulated glazing),
operability and performance are still a concern, as well as (you guessed
it) cost.  There is a serious consideration for aluminum clad wood, all
wood is a lot pricier, all aluminum is a lot fatter, and then there's a
local low bidder who is pushing solid vinyl (?!) that will not stack up in
appearance.
Is there any good analysis, otherwise concensus, or, I'll settle for
informed suspicion as to how these various systems perform in such sizes?
While we're at it, how about vinyl clad wood or the paintable fiberglass?
--Jim Rhodes