The real cost of removing historic windows…

On Thursday I was in Athens, GA to give a talk on the energy efficiencies and ‘sustainability’ benefits of restoring historic windows as opposed to ripping them out and tossing them in the landfill.  Sponsored by the Athens-Clarke Heritage Foundation and other local preservation interests, the emphasis of the symposium was on enegy savings in historic buildings.

After the meeting I had the pleasure of getting a tour of the University of Georgia’s historic North Campus with campus architect Scott Messer.  Come to find out, Scott has every bit the fetish for old windows as I do so we had great conversations about past and future failed and successful efforts to retain much of UGA’s 150+ year-old fenestration.  Hopefully my company, Double Hung, LLC, will be traveling back to Athens some time in 2008 to do our restoration thing on at least one of their extraordinary structures.

Messer shared with me the latest in a growing body of research that calls into question the wisdom, economics, ‘green-ness’ and asthetics of replacing original windows.  Published  by the Association for Preservation Technology, authors Walter Sedovic and Jill Gotthelf have put together a heavily footnoted treatise that forcefully argues…

What Replacement Windows Can’t Replace: The Real Cost of Removing Historic Windows. (PDF file)

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  1. Chris
    Posted November 8, 2007 at 1:13 pm | Permalink

    Re: “What Replacement Windows Can’t Replace:…”
    I will print that out and tape it to the wall.
    In regards to window replacement, a nice wood storm window over a properly restored wood window is probably the most efficient use of home improvement money there is for the owner of a vintage house. Beside the fact that replacement windows destroy the visual integrity of a true muntin window, the payoff is not that great. Money is better spent on a properly sized and installed quality HVAC system.

  2. Posted March 5, 2008 at 5:26 pm | Permalink

    Re: What Replacement Windows Can’t Replace: The Real Cost of Removing Historic Windows WALTER SEDOVIC and JILL H. GOTTHELF

    “high-quality equivalent replacement units have been shown in practice to cost as much as three times that of restoration.�

    While the cost of high quality, high performance replicate landmark windows are more expensive than typical vinyl, fiberglass, aluminum, clad or semi-custom wooden replacement widows, to say that the high quality equivalent has been shown in practice to cost as much as three times that of restoration is somewhat imprecise.

    The fact of the matter is that the cost of restoration depends on the condition of the original window, the extent of its damage. Some original windows are simply too far gone to warrant extensive epoxy consolidation, re-glazing and weather-stripping. There are, after all, some improvements to window fabrication techniques since the inception of casement and double hung windows about three hundred years ago that should not be discounted off-handedly.

    Putty glazing is an excellent example.

    First, let me say up front that I am not an impartial observer. I am President and CEO of The Woodstone Company and we’ve been manufacturing replicate historic wood windows for 30 years.

    With the advent of silicone sealants, for example, we now find that installing glass in a window, be it single pane or sealed insulating glass, is better done from the interior surface, not the exterior as was the case with most windows until about 20 years ago. The longevity of the seal between the glass and the wood of an interior glazed window is many times that of a traditional exterior putty glazed window and I defy anyone to recognize an aesthetic difference between the two methods when viewing the window from ten feet or ten centimeters – unless of course you appreciate the cracked and pitted appearance of putty glazing after only a couple of years of exposure.

    And it’s a myth that painting the putty glazing and lapping the paint on to the glass adds significant longevity to the putty. As soon as the putty cracks and separates from the glass and/or the wood, water infiltrates into the wood joinery of the sash. The first sign of damage is the commonly seen peeling of paint at the lower ends of the vertical stiles. Then the wood joinery itself becomes damaged.

    If you’re an epoxy consolidator, you have a never ending market for your services. But no amount of epoxy can correct the deficiencies in this antiquated design. You will be restoring these sash many times over the life of a well designed wooden replicate window, hence the question is, once you go through the restoration process three times, the worst case scenario – as the above example provides, you will likely have much more energy and cost invested than had you spent the additional money and purchased a well designed replicate window.

    There are many more aspects of replication vs. restoration to consider as well and I appreciate and look forward to the opportunity to discuss them with you.

  3. Posted March 5, 2008 at 8:17 pm | Permalink

    What a great response, Jay. Good to hear differing opinions.

    First, regarding this… “unless of course you appreciate the cracked and pitted appearance of putty glazing after only a couple of years of exposure.”

    I can’t speak for all restoration companies, but I’m sitting here looking at my very own 1921 windows in my own house which I reglazed 12 years ago. There is none of the cracking or pitting you speak of, the putty is as smooth as a baby’s butt. Perhaps some people just don’t know what they are doing.

    Also, don’t bite on the “as much as three times that of restoration” hook. “As much as” must have meant somebody’s replacement fenestration was made out of 200 year-old mahogany or some such. In practice, we both know that statement was a stretch. But I guarantee you that a properly executed restoration is MUCH less expensive than – here’s the correct term – “comparable” replacements such as what your fine company manufactures even over a 50 year life cycle.

    All that said. I will be contacting you via email. I am in desperate need of a resource such as what Woodstone provides as an augmentation to our burgeoning business.

  4. Posted March 6, 2008 at 10:39 am | Permalink

    David: Thanks for yuor comments and I look forward to your email.

    Re: There is none of the cracking or pitting you speak of, the putty is as smooth as a baby’s butt. Perhaps some people just don’t know what they are doing.

    Exposure to the elements is the most important consideration. If you have storm windows and the window doesn’t receive a lot of sun exposure, the putty can stay pristine for many years. But even with storm windows, direct sunlight from southeast to southwest exposures will create significant changes in temperature and commensurate shrinking and expanding of the putty, the glass and the wood. Glazing points tend to come loose and the integrity of the seal decreases allowing water from condensation alone to begin to work even more on the putty.

    Re: “As much as� must have meant somebody’s replacement fenestration was made out of 200 year-old mahogany or some such.

    We manufacture the vast majority of our windows in managed forest Genuine Mahogany, arguably the finest sash wood on the planet for many reasons. Mahogany’s resistance to decay is exceptional. It simply doesn’t decay unless it’s used as a fence post and driven into the ground. Mahogany, as a consummate pattern wood, is one of the most stable wood species. In other words, a well made Mahogany sash ought to require less restoration than any other window sash there is.

    Re: “But I guarantee you that a properly executed restoration is MUCH less expensive than – here’s the correct term – “comparableâ€? replacements such as what your fine company manufactures even over a 50 year life cycle.”

    I have to disagree, unless you are restoring a comparable Mahogany, White Oak or Cherry sash. Most historic windows were fabricated in old growth Northeast White Pine, which was an excellent sash wood in its time, but no longer available. At the turn of the century and up to the mid 1950′s White Oak was often used for high end wooden windows, especially those huge double hung windows many of peered through when we were in elementary school.

    And I can give you a specific example of restoration vs. replication on the oldest municipal building here in Vermont – the Rockingham Meeting House Circa 1787. We restored several of the windows and had to replace several with precise replicates in 1981. After 25 years the replicates are in excellent condition, but the restored epoxy consolidations require more regularly scheduled maintenance. The building is featured on the back cover of the Woodstone Tradition and Technology Window manual.

    Again, replication vs. restoration depends primarily on the condition of the window being considered, not to mention the prospect of included authentic true divided lite insulating glass (IG) in a replicate window. One of the most damaging aspects to old windows, with and without storm sash, is condensation. Warm Edge IG eliminates condensation and further increases the longevity of the replicate sash. And Woodstone manufactures IG sash with muntins as narrow as 7/8� and with Warm Edge spacer colors closely matching the paint color of the sash, an observer will be hard pressed to see that it’s IG and not single glazing.

    Thank you for taking the time comment and I look forward to continued discussion.

  5. Posted March 6, 2008 at 5:50 pm | Permalink

    But Jay, We aren’t in New England. Down here we have original growth southern yellow pine or longleaf – and mostly heartpine at that. I’ll put that material up to any mahogany you can come up with.

    Admittedly mahogany is far superior to anything currently available and the old growth stuff is long gone as a viable source, but I’m advocating for restoration, not for replacement. If historic windows need replacement for whatever the reason, I’d certainly go with mahogany (or, perhaps, Spanish cedar), but the typical window in this part of the world just isn’t in all that bad of a shape to justify the expense.

    Of the hundreds of old windows we have restored, perhaps 20 – 30 were “beyond repair”. There is just no reason to replace them when they are imminently repairable.

    Most houses down here DO have storms – wooden or aluminum. Our glaze putty will go many deacades with regular maintenance. We’ll just have to disagree on that point.


  6. Posted March 7, 2008 at 10:51 am | Permalink


    Southern Long Leaf Yellow Pine is known best for its structural properties and rates with Oak and Douglas Fir. Genuine Mahogany, not African Mahogany, not Sapele, not Philippine Mahogany or Luan (which isn’t Mahogany at all), has nearly as high a structural rating. Woodstone, for example, fabricates its sash as a standard to provide over 60 pounds per square foot structural load, exceeding the force of a category five 150 mph hurricane.

    But Southern Yellow Pine is not nearly as stable as Mahogany or Northeast White Pine. Mahogany is known for its ‘pattern making’ properties, i.e. stability. Southern Yellow Pine, even its heartwood in a quarter sawn configuration, is prone to warp in the milling process and after its exposed to the elements. One need only observe the multitude of pressure treated decks in the neighborhood to see this movement and the vast majority of pressure treated deck lumber is Southern Yellow Pine.

    Southern Yellow Pine is only’ moderately resistant’ to decay and only then if its ‘old growth’, as is the case with Northeast White Pine. Mahogany, on the other hand, is one of the most decay resistant species available, old or new growth, even exceeding the properties of Teak (because most of the Old Growth Teak is gone and not available in sizes required.). It’s listed along with Walnut, Cherry and White Oak (not Red Oak). There are other species, like Locust, that exceed the decay resistance of Mahogany. But Locust and the others (see the list referenced below) is also not a good wood species for milling purposes.

    Take a look at par. 3-10 of the U.S. Wood Engineering Handbook for details on these wood species. It’s listed under Other Resources on the Woodstone Home Page or go straight to the U.S. Wood Engineering Handbook web site:

    Interestingly too, storm windows are not ‘historic’ features, at least not in the sense of windows built before the Civil War. Early glass manufacturing processes could not consistently produce the large pieces of glass commonly used in storm sash. Some early window glass was actually ‘blown’ glass, e.g. Bull’s Eye or Crown Bullion. That’s why really old windows are small true divided lites. If a musket shot or arrow broke a piece of glass, better to replace one small pane than an entire window sash.

    There are other reasons to consider replication over restoration as I mentioned earlier. Sealed Insulating Glass increases the longevity of the wood joinery in any sash because it significantly limits condensation (most of which emanates from the interior of a house, not the exterior). Condensation can be as damaging as rain water.

    But I’m not advocating sash replication over restoration in all cases. As I said earlier, if a sash and its jamb are not severely damaged, restore it. But Woodstone specializes in matching historic details when replication is required. And it’s not just the sash that are considered. Woodstone provides weight and pulley double hung functions, for example, with jambs. Woodstone uses only non corrosive materials, e.g. stainless steel screws and brads, brass and bronze pulleys and chains, marine rope instead of cotton laundry cord, 50 year silicone sealants, and sealed weight boxes for air infiltration standards that exceed the standard National Window and Door Association by 300% (independent test lab reports available upon request).

    In other words, if there is any doubt as to whether or not you should restore or replicate, you can’t go wrong replicating; and you can’t achieve the performance of a replicate window in a restoration of old details at the same price.

    David, I would appreciate it if you provide any data you have to the contrary. My purpose here is to expand my horizons, not ‘win’ an argument or ‘agree to disagree’. That doesn’t serve you or me or our clients.

  7. David Wharton
    Posted March 8, 2008 at 3:24 pm | Permalink

    What an informative discussion.

    I only wish the usual, real-life dilemma here in Greensboro’s preservation environment were whether to restore an historic window or to replicate it with high-quality mahogany.

    Normally people just want to remove historic windows that are usually in pretty good shape and replace them with an inexpensive vinyl-clad product, often with plastic, fake muntins mounted between the panes.


  8. Chris
    Posted March 10, 2008 at 2:17 pm | Permalink


    I can relate to Mr. Eshelman’s perspective as it pertains to replacing a window. It’s great that he can replicate old windows using durable wood products and efficient glass. Plenty of places where that approach might be best.

    I think the point he is missing is that with a replica, you no longer have the original.

  9. Posted March 16, 2008 at 9:07 am | Permalink

    re: – with a replica, you no longer have the original.

    Again, an historic window in reasonable shape is a candidate for epoxy consolidation. But a window that is significantly restored with epoxy is… well, epoxy, not the original. And in many cases, at least in the case of buildings over 200 years of age as we have here in the colonies, the historic window being replaced wasn’t the original either.

    The point being missed is that the object to restoration or replication is to maintain the original architectural design, not the material. And if the design can be replicated and easily maintained, and if the replicate window can be made energy efficient, that’s the best of both worlds.

    At Woodstone we’ve restored and we’ve replicated. What pleases us about the replication outcome is that very few people can tell the difference.

  10. Posted September 7, 2008 at 9:19 pm | Permalink

    Jay, I have original putty that was installed 80 years ago and it’s still intact. The only windows we’ve had any issues with are the south-facing ones, and I’ve restored all of them. I know there is a need in the market for new windows and I applaud the companies that try to do a better job, but really the future generations who inherit our miserable attempts at architecture will suffer because most of the new building products aren’t repairable. Things have to be repairable to have a super-long service life.

  11. Posted December 2, 2008 at 12:27 pm | Permalink

    Kurtis: Typically, glazing putty (and the steel points holding the glass in place) are rendered in need of repair most on southern and southwest exposures. The steel points will rust in any case if, for no other reason, than the point being subjected to condensation from time to time.

    I have some north facing putty glazed windows in my house installed about 35 years ago that are still in good shape too. But I suspect, without asking you to confirm, that your putty glazed windows have storm windows protecting them (as do mine), which might explain the longevity.

    Further, your windows likely do not have insulating glass [IG]. Most putty glazes are not compatible with the sealants used in the IG seal. And, if they were, the windows wouldn’t typically include a storm window to protect them.

    Again, we manufacture historically accurate wooden windows from wood species like Mahogany, White Oak and Cherry, all of which having a high resistance to decay; and our IG glass can be easily repaired or replaced from time to time. We fully expect our windows to last for 100 years or more. And we build in the maintenance friendly aspects that allow these windows to be upgraded from time to time with improved technical advances in weather-strip and IG. And while these windows are expensive on a per unit basis, when one compares the price to the useful life in years, the cost per year is significantly less than even the least expensive vinyl or aluminum alternative – not to mention the savings from not having to throw windows in a landfill every 10 to 20 years.