For years, window replacement companies have implied that the greatest source of energy loss in homes is through old windows. The evidence I have seen suggests otherwise.
First, the Nashville Electric Service cites a study conducted by Southface Energy Institute showing that the greatest areas of energy loss in the home are air infiltration, at 28%, and air conditioning duct leaks, at 21%. Air infiltration includes holes drilled into the exterior and interior walls, dryer vents, electrical items, and plumbing lines from the crawl space.
Second, a recent home energy audit conducted by E3 Innovate on a 1930’s craftsman-style home here in East Nashville identified six areas needing attention. None of the six items involved window replacement. The top three areas to reduce energy loss identified by E3 Innovate were to reduce air infiltration, to insulate knee walls, and to insulate attic crawlspace.
Third, my own experience of renovation design on historic houses has confirmed both the Southface Energy Institute report and the recent E3 Innovate home energy audit.
This is not to say that new windows are not energy-efficient, because they are. However, air infiltration actually occurs inside the wall around the edges of the window, so replacing a window cannot solve your problem. I have seen windows replaced in a house where other glaring sources of energy loss, such as a lack of insulation in the attic or the crawl space, were left untouched. You simply cannot expect this to reduce your energy bill.
For the same energy conservation benefits, you can add cost-effective storm windows over your historic windows and get the best of both worlds. If you already have storm windows but yours were installed prior to the 1980’s, you may need to consider replacing them.
Windows are both a defining characteristic and an integral part of historic homes. Replacing original windows with vinyl windows reduces the value of your beautiful home.
For more information on energy efficiency in historic homes, check out Lynn’s blog at http://www.taylormadeplans.com/blog/