Need Help Greening Your Wood Windows? Check this out!

Posted on: July 18th, 2008 by Patrice Frey 4 Comments

windowgraph.jpgWindows tend to be a "flash point" in the dialogue between green building advocates and preservationists, with preservationists preferring to retain character-defining windows, and green building advocates often arguing that it is necessary to replace windows to improve energy performance. It's safe to say that the National Trust gets more questions about this issue than any other related to the Sustainability Initiative, and we receive many requests for step-by-step technical assistance for greening historic windows. Our new Tip Sheet for Historic Wood Windows addresses many of these questions. The tip sheet, which was prepared by Rebecca Williams of the Northeast Office, explores the environmental benefits of retaining wood windows and offers suggestions for greening windows.

Interestingly, data from the U.S. Dept. of Energy finds that windows usually account for about 10% of energy loss in buildings, while walls, ceilings, and floors account for 31% of thermal loss. And as Barbara Campagna and I have mentioned in previous blog entries, studies have demonstrated that properly weatherized historic windows perform about as well as new, thermally resistant windows. Nevertheless, there continues to be concern about the issue of windows, and the widespread perception that going green automatically requires replacing windows.

The Windows Tips Sheet is really just the beginning of our work on the issue. Because this topic is so important, we’ve established a comprehensive Historic Windows Assessment Project to study windows more comprehensively.  Thanks to partial funding from the National Center for Preservation Training and Technology, the first phase of our Historic Windows Assessment Project will compare historic windows to the latest in green technology and create a "decision matrix" to help building owners decide the most appropriate path to improving their windows. The research will be undertaken with scientists from the Lawrence Berkeley National Laboratory in California.

The second phase of the research will look at windows in the context of thermal loss in the entire building to help demonstrate the importance of looking at buildings holistically, rather than focusing on one source of thermal loss. The third phase will look at the total life cycle impacts associated with replacing rather than reusing an existing window. In other words, instead of just looking at energy saved through operation of a new window, this study will look at the environmental costs of manufacturing new windows and replacing them periodically since they typically cannot be repaired.

In the meantime, have a look at the Tip Sheet, and tell us what you think!

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4 Responses

  1. John Leeke

    August 12, 2008

    Yes, exterior storms are good. Or, interior “storms”, sometimes called “air panels.” Learn how to make your own, and find a source for a commercial product over at the Historic HomeWorks Forum:

    I guess the lesson is that there are many specific treatments that can be applied to existing windows to save their historic character and improve energy efficiency.

    In our work we always give each window individual consideration rather than simply applying a treatment to all windows without much thought (as is frequently done on many projects). In this way it is possible to save character and money.

    John Leeke
    American Preservationeer

  2. Tim Storey

    September 6, 2008

    I tried to find the graphic at the DOE site, but the only one I could find shows windows at 26% and it doesn’t show all the categories yours does. Could you tell me where to get that? I’ve seen a range of 10%-25% in literature (preservation) before, but I haven’t found support for the 10%. (It could be from houses with no attic insulation I suppose.) Thanks.

    Also, any ideas on why our government is so big on replacement windows when it’s bad for the environment, local economy, the homeowners budget, and they don’t help much? I could be cynical and theorize about lobbyists from the construction industry…

  3. John Leeke

    September 16, 2008

    Tim Writes:

    “Also, any ideas on why our government is so big on replacement windows when it’s bad for the environment, local economy, the homeowners budget, and they don’t help much? I could be cynical and theorize about lobbyists from the construction industry…”

    Of course, this is exactly the reason. The vinyl pirates steal the good old windows from our homes, then every 8 to 12 years they come back to get more of our money because their sleazy plastic windows need replacing. But don’t worry, more and more homeowners are talking to each other over the back fence and realizing that they have been bamboozled by the pirates. Now many are seeing that it is a better deal to maintain their existing wood windows.

    John Leeke,
    American Preservationeer

  4. John Leeke

    March 4, 2009

    As Tim asks, what is the source for the figures in the pie chart above?

    We need this backup info if we are going to save windows from the vinyl pirates!