Window Muntins: What They Are and Why They Matter

The history of window design reads like a thriller novel, packed with intrigue, suspense, and—wait, who am I kidding? While the architecture of windows can be quite fascinating, much of the history is derived out of the necessity of the time the windows were created. One such example is window muntins, an often misused and misappropriated term, that has at its core a pretty simple meaning.

Use the links below to skip ahead in this post:

• What are window muntins?
• Are muntins still used on windows?
• How do I know if my windows have real muntins?
• Why do muntins matter?

What are window muntins?

So what are window muntins? Well, the original term actually came into being in the middle ages. Muntins were the frames used to separate and hold smaller panes of glass together to make much larger ones. These now decorative items arose out of necessity.

At the time, it wasn’t practical or possible to make large panes of glass. So to make large windows, muntins were born. This is why in older homes, and especially in Europe, you will find genuine muntins.

Are muntins still used on windows?

The simple answer is usually not. The reason is again simple: we now have the ability and technology to make larger panes of glass and there is no need to piece together smaller panes in order to form a larger one.

“But I’ve seen these,” you say. “On modern windows.”

Actually, you have probably seen “grids” instead. These are decorative pieces designed to mimic the look and feel of real muntins, but most of the time they are not actually separating panes of glass.

Part of the reason is efficiency. Double and even triple-pane windows made in large continuous sheets mean the temperature from the inside of your home and the outside can be separated from each other more efficiently, which means your heating works better in the winter and your air conditioning is more economical in the summer.

How do I know if my windows have real muntins?

Aside from calling a professional to look at them, you can often tell by looking at your window at an angle, and how light is reflected through the window. There are many simulated divided light (SDL) windows out there, and the likelihood is that if your home has been renovated in the last few decades and if the windows were replaced, the separation is now simulated using a grid.

That doesn’t mean they are not true divided light (TDL) windows or even the originals. Looking at an angle, you can often see if the wood goes all the way through the glass, which means the muntins may be original. You can also tell by reflected light. It is rare for TDL windows with real muntins to end up at exactly the same angle, so reflections are often slightly off-kilter from frame to frame.

Could they be replacements that are non-period? It is possible, but not likely. Custom, TDL frames with real muntins can cost up to ten times what windows with modern grids will cost, so if you have real muntins, it’s likely the windows are originals.

As a note, the home in the photo above has single pane metal windows with muntins. In the photo below you can see how glass is removed from between the muntins before the window is replaced.

Why do muntins matter?

What difference do muntins make, and why do they matter? While modern architecture is often obsessed with open light and unobstructed views, there are many styles where muntins were popular.

If you are looking to restore your older home to the original look, muntin equipped windows may be a part of that. It is up to you whether you have the old windows restored or replaced with more modern double-paned ones.

Otherwise, there are affordable or custom modern options available, from grid replacements to TDL windows that can be costly but beautiful. The window look you go for in the end is entirely up to you.