True divided light windows and their modern-day counterparts.
It should be understood that conserving old windows is the “greenest” option: they are endlessly repairable and easy to upgrade for energy efficiency and comfort. For those buying new windows, find good news in recent aesthetic improvements. I treasure the few original singlepane casement and double-hung windows that remain in my 80-year-old rustic cottage. But without the old, handbuilt, wooden storm windows to create effective double glazing (trapping insulating air in-between), I’d be awfully cold in winter. The cottage came with a few not-so-sturdy replacement windows that long ago outlived their usefulness. They don’t match other windows in the house, and they aren’t double-glazed.
Replacement options, in my case, range from real divided-light windows with multiple, separate panes of glass to simulated divided lights, an increasingly popular option for windows since they were introduced in the last decades of the 20th century. The latest versions of simulated dividers are much more realistic than early snap-in or removable grille versions, which lacked depth and were poorly proportioned, especially in relation to historical windows.
SIMULATED DIVIDED LIGHTS
Although window manufacturers continue to offer a range of simulated divided lights (or SDLs), the better offerings have dividers that are permanently attached to the interior and exterior panes with a durable adhesive. At minimum, the dividers set in the interior of the window should be made of wood with a realistic muntin profile. If you can afford it, specify a coordinating profile in a weather-resistant wood for the exterior—it will make the windows “read” architecturally from a distance.
To eliminate the flat reflection that make the SDL look fake, opt for windows where the overlay grids are darkened underneath to create a shadow effect, or specify spacer bars between the two panes of glass that follow the pattern of the overlay. Both techniques make it harder to tell that the muntins don’t go all the way through the window.
TRUE DIVIDED LIGHTS
That said, true divided-light sash (TDL) reflects light differently. Multiple panes of glass each reflect light, so that the reflection in the window dances subtly as you pass by. Window frames and muntins on TDLs also tend to be thicker, throwing deeper, more architectural shadow lines.
For a historic or especially significant house, custom windows with true divided lights may still be the best option, especially if the house is subject to local historic landmark requirements. Interestingly, the computer-numeric-control (CNC) capabilities now driving so much of contemporary manufacturing make it much easier to replicate a historic
muntin profile, even in a window made using modern methods that piece together windows from many tightly precision-cut parts.
A schematic view of a muntin on a double-glazed, true divided light from Heartwood Windows (see opposite), for example, shows a muntin in a traditional moulding profile that appears to pass through both layers of glass. The muntin is actually passing between individual blocks of glass and wood that make up each double-glazed “light” in the window sash.
On the exterior side, the muntin is pinned in place against the outer glass with wood stops. The schematic only suggests the many parts needed to compose a double glazed “light” that looks like a 200-year-old windowpane.
AFFORDING CUSTOM WORK
While custom, true divided-light multipane windows made of solid wood can be pricey at upwards of $2,500 per double glazed unit, smaller companies may offer more affordable pricing. Working directly with a manufacturer is a good
The latest types of simulated dividers are much more realistic than early snap-in or removable grille versions, which lacked depth and good proportions.
way to ensure that your “replacement” windows match the old originals still on the house. For those on tighter budgets (like me), stock double-glazed windows with wood grilles fixed to the inside of the sash are more affordable at $200 to $500. Another alternative is to keep (or buy) single-glazed windows and add storms, or interior glazing panels that typically cost $24 to $36 per square foot. Have any remaining original windows reconditioned by a restoration pro.
I’d do that, but I don’t have the option: my old windows are all but gone.