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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.

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"This was one of the best experiences I've ever had with a company. I ordered the windows in November and was told they wouldn't be here until July. That kind of delay the new norm so I wasn't a bit upset with the timeline. I was given an early present when they called to say the windows would be in at the beginning of May. We agreed on the week of May 16th to do the installation, there were 30 windows and a sliding door to install. They arrived promptly on their scheduled install date, and got straight to work. By the end of day one, they had all the upstairs windows complete and their work was incredible. Day two came with more of the same, the crew showed up promptly, got straight to work, and when they left they had every window downstairs installed. The third day they again arrived on-time, and got to work installing the door. The door and windows are perfectly installed. The two lads that did the installation did a phenomenal job, and were friendly to boot. I would give them more business if I had any :) The service I received from the company was great. They kept me abreast of anything that was going on with my order. I appreciate my concierge, Christina, she was good at communicating timelines and getting everything scheduled."

Lane Maxwell
Jun 28, 2022

"The two installers were great! They were polite and hard working and they cleaned up all the outside and inside. It was like they were never here. As for the windows, I love them, not only looks great, they are efficient. Now every window in my home has Renewal by Anderson."

Mark Palsgrove
Jun 23, 2022

"We had the pleasure recently of having Andersen replace all of our windows. From the very first interaction with the office personnel through the completion of the project, they have been nothing but professional. From Brian our sales rep to Christina the appointment scheduler, they were a pleasure to interact with. Installers Keith, John, and Evan were fantastic to work with. They went above and beyond to repair an area which was slightly damaged during the removal of a window...caulked and painted it. They took extra precaution to ensure the floors were covered while working inside and cleaned up each day inside and out. We love the look of our new windows and can't wait to enjoy the savings in utilities they'll provide. Thanks so much Renewal by Andersen!!"

Kevin Corrigan
Jun 15, 2022

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