[Greenbuilding] old wood windows (was Exterior insulation retrofit)

Chris Koehn chris at koehn.com
Sat May 7 15:27:22 PDT 2011

This Old House did a project several years back with historic windows that were restored for energy efficiency. Since the house is really old (1700's) there is an historic element which needs to be considered: these windows were undoubtedly hand made. Here's a link: <http://www.thisoldhouse.com/toh/article/0,,211760,00.html?order=ASC&expand_all=true&page=3&per_page=10>

The project brought to light a couple salient points:
• Regardless of the age of the window, consider the quality of the wood. Most older wood windows were made from old growth trees, and as such has greater stability and rot resistance than 2nd growth. 
• The vast majority of energy inefficiency in older windows comes from leakiness, not poorly performing glazing. It's much easier to retrofit high quality weatherstripping than it is insulating glass (although many companies, primarily in the east where there are more old wood windows are quite adept at this- here's one: <http://www.marlowerestorations.com/window_restoration.html>). 

I ran service for Pella for a number of years in the '80's. Older wood windows, made of white or ponderosa pine and well maintained, survived well and were prized for their quality. Pella introduced aluminum exterior cladding in the '70's. FWIW  I never saw moisture behind the cladding- either from leaks or condensation- during my years there.


Chris Koehn

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