Q. I live in a 1940 condo complex with the original single-pane windows. Replacements with higher R and U factors are my choice; however, some believe that restoring the windows would be aesthetically more pleasing. How would you address the issue? Thank you.
JANET W., Brookline
A. That is a very good question, and the answer can be complicated. You do not say what kind of windows your condo currently has. Are they metal casement? Wood double-hung? This may have some impact on the answer. Also, if it is a condo, you may have restrictions or stipulations as to what is allowed.
Generally speaking, restoring old windows can achieve a reasonable upgrade in energy efficiency while maintaining their historic look. You must make sure, however, that the voids around the window are insulated and caulked properly. Also, a properly fitted storm window, whether exterior or even interior, will go a long way to increasing the energy efficiency. There are specialists who do this kind of work.
If you do want to go the way of a new double-pane, low-E, low-U window, there are certain attributes you should consider.
There are two types of replacement windows. In the industry, the term “replacement’’ means a window that fits within the existing opening without undoing and redoing the sill and trim. Usually this type of window will have an additional frame, though small, that fits into the existing opening. This generally reduces the net amount of glass and increases the thickness of the window frame. This thickness varies by window manufacturer, and may not be aesthetically compatible with what you or your condo association would want.
Otherwise, you can replace your old window with a “new construction’’ window, which would not have the frame-within-a-frame look. It can be installed in the existing location of your window, but this would mean taking out the existing frame and casings, installing the new window, reinstalling all the trim, and doing patching and painting. This would look the best while giving you the energy efficiency you are looking for, but it would cost more than a replacement window to install.
In either case, assuming that your windows have a grid and there are individual panes, the small wood pieces that hold each piece of glass in place are called “muntins.’’ When deciding on whether to replace a window, you should look at the muntin profile and width. Each manufacturer has a standard profile that may or may not match your muntin. Older windows generally have narrower ones, around ¾ of an inch wide. Some new window manufacturers have only 7/8 of an inch as their narrowest.
The exact profile of the muntin may be important to retain a historic look. Some window companies have muntins that are relatively flat or plain, whereas old windows typically have curved “ogee’’-style muntins. “Ogee’’ means it has an S-shaped profile. Try to find one that matches as closely as possible when considering which way to go.
Another feature to examine when choosing a new window is how the muntins meet the edge of the window. Is it in a tapered, graceful way, or do they look a bit blunt?
Finally, be sure to understand the materials used. Wood is nice on the inside, while some type of protective layer, called “cladding,’’ on the outside is good. Each window manufacturer has its preferred cladding material, such as aluminum or vinyl.
Once you look at all these factors, you can make a more informed decision.
Chris Chu is an architect in West Newton who specializes in residential design. Send questions to Address@globe.com.
