Authentic True Divided Lites vs. Simulated Divided Lites

Woodstone® Authentic True Divided Lites vs. 

…Simulated Divided Lite ‘Superiority’ in Windows and Doors

Fact or Fiction?

Under the guise of recent technical service bulletins, some Insulating Glass (IG) manufacturers are reporting that SDL (Simulated Divided Lite) IG is “significantly more beneficial” than Authentic or TDL (True Divided Lite) IG. But careful review of the claim exposes flaws in the logic. Let’s consider each claim.

Reduced Material and Labor costs?

In a typical wooden SDL Window or Door, there is a wooden full lite frame, a full lite IG unit with a metal grille inside the IG air space, and then two additional wooden grilles – permanently glued to the sides of the IG and the SDL window or door frame.

An Authentic Woodstone® True Divided Lite (TDL) Window or Door has one wooden Divided Lite frame in which the TDL IG units are installed.

Labor savings realized by installing one large SDL IG unit rather than several smaller authentic lites are offset by the additional labor and material required to fabricate and glue the two additional wooden grilles to the glass and window or door frame. 

Reduced air and water infiltration?

Read the performance standards of any window or door before you purchase it. Woodstone® fabricates TDL windows and doors that meet or exceed the most stringent industry standards. 

Improved Thermal Performance?  

Woodstone® TDL windows and doors can include the same high performance glazing used in SDL windows and doors.

Large IG units have less seal edge stress than small IG units?

This is true. And it’s why the Insulating Glass Certification Council (IGCC) standard requires IG fabricators to annually test only small IG units. And Woodstone’s® TDL Insulated Glass has the highest IGCC CBA rating available.

Small IG units installed in high altitude locations require breather tubes to offset air pressure?

True again. But large IG units fabricated at sea level and installed at high altitude better have breather tubes too. Otherwise the air pressure differential will bow the glass and stress the seal.

Condensation is reduced with SDL units?

 Stainless Steel Spacer is about 4 times less conductive than the Aluminum Spacer with which some SDL units are fabricated.

However, the Composite IG spacer Woodstone® uses in its TDL IG units is 85 times less conductive than the Stainless Steel spacer inside the so-called Superior SDL air space.

SDL IG requires only one Federal identifying logo where Safety Glass is required?

According to the 780 CMR 2405.0 SAFETY GLAZING building code, when logos are specified, only one logo per sash or door is typically required with TDL too. In fact, in some cases, ‘the code’ allows for a Certificate of Compliance in lieu of any logos.

Always check your local building codes.

Reduced Breakage Potential?

At Woodstone®, we were somewhat surprised by this claim. Not because it’s false (and it is, patently false), but because it’s the breakage potential of the SDL that creates the greatest liability for the window manufacturer and the consumer.  

Woodstone® specializes in fabricating accurate landmark historic replicate windows and doors. Consider what happens if the IG breaks or the IG seal finally does fail. If your window or door is anything like the Woodstone® Palladian pictured above, and wind-blown debris or a stone thrown from a lawn mower breaks the IG, or you accidently scratch, crack or break the glass while cleaning it or doing routine maintenance… then what?

Glass can be damaged or break from time to time. Broken IG in a so-called Superior Divided Lite (SDL) unit requires expensive replacement costs. With an Authentic or True Divided Lite (TDL) Woodstone® window or door, just replace the small pane of IG.

Furthermore, most SDL units are significantly heavier than TDL windows and doors because the glass must be thicker and SDL IG is typically incompatible with historic restoration glass.

Even shipping and handling SDL units poses a higher breakage risk compared to Authentic True Divided Lite windows and doors.

The Final Analysis.

Using SDL IG in a vinyl replacement window is one thing. But as a long term investment, using SDL in a high quality historic landmark window or door, designed to last for generations, fabricated with restoration glass, fine lumber and hardware, and unique custom moldings and finishes inside and out, is another matter entirely. After all, high quality Woodstone® TDL windows and doors will last significantly longer than the duration of any limited IG warranty.   

Consider this: When a window or door is expected to last for generations, as have many of the windows and doors Woodstone® replicates, how many times will the so-called Superior SDL window or door have to be replaced - in its entirety – and at what future cost?

Most SDL IG manufacturers making the claim of superiority only warrant the replacement of the IG, not the window or door in which the IG is installed. And they typically honor the IG warranty only to the manufacturer purchasing the IG unit, not to the end consumer.

This explains why many SDL window and door manufacturers warrant their products to the consumer for shorter periods of time, even when the SDL IG is warranted to the manufacturer for longer time periods.  

Always read the warranty.

Authentic True Divided Lites (TDL) …

    …vs. Simulated or ‘Superior’ Divided Lites (SDL)? 

                                                            You decide.