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Window Mullions and Muntins – What’s the Difference

When we think about the parts that make up our windows, we usually think about panes of glass, sills, frames and casings. While you may not have heard about mullions and muntins, it is quite possible that you probably already have them on your windows or even your patio doors without even realizing it. So, what are muntins and mullions?

Window Mullions and Muntins - What’s the Difference

Window Mullions

Window mullions are the vertical bars that divide two or more panes of glass in a window. Although their main purpose is to provide rigid support, they can also serve as a decorative element. Prior to the Victorian era, it was not possible to manufacture large sheets of glass, so large expanses of windows were achieved by providing them with support via the use of mullions.

Window Muntins

Window muntins, on the other hand, are sash bars made of wood or metal strips that separate and support the glass panes in a window. Muntins only refer to the inner vertical pieces. While they are most associated with windows, they can also mean any kind of vertical divider used for doors, wood panels and even furniture.

To put it simply, muntins are inner, vertical elements that separate panes of glass in a multi-pane window while mullions are single vertical supports used in multi-pane assemblies. Not many window companies make a distinction between muntins and millions because few homeowners care about this, and, oftentimes, they are used interchangeably. A more buyer-friendly term that window manufacturers use is grille.

Whether it’s French doors or your traditional casement window, you will probably see these elements in most houses in your neighborhood. If this is something you care about when looking for windows to purchase, give Renewal by Andersen® of St. Louis a call (314) 332-2364, or fill out our contact form to speak to one of our window experts.

Reviews

"The installation crew was very professional and answered what questions I had. And they cleaned up when they were finished. We're very pleased with our windows & patio doors. Highly recommend Renewl by Anderson."

Pamela D
Feb 13, 2023

"Very pleased with installation of six windows and a ProVia entry door. I love the look of the windows and door. I am pleased that my wife is thrilled with the look of the door. She is very pleased that the bronze color fits in well with the color of the brick."

Terry S
Feb 8, 2023

"I just had my Renewal by Andersen windows installed and couldn’t be happier, the entire process went very smoothly. The windows are high quality and look great. But the installers Roy, Zack and Jordan were the stars, they introduced themselves upon arrival walked me thru everything they were going to do and when they finished took me to each window to make sure I was completely satisfied. They were clean and courteous and I would definitely recommend and have them work in my home again."

BOB B
Feb 6, 2023

"Wonderful experience with knowledgeable, competent employees. We had Andersen windows in a previous house & didn’t even consider anything else this time. After replacing our patio door almost two years ago, we replaced all our windows this year. What a difference over builder-grade windows, especially in the really cold temperatures we’ve had this year. Andersen windows may be a little more expensive than other brands, but they are top quality."

Susan S
Jan 31, 2023

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