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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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"Scheduled for December, Installed in October, High quality windows and Excellent install team. I haven't seen people work together like that in years. I am definitely impressed."

Raymond Mills
Oct 13, 2022

"The service provided by Renewal by Anderson is great, both on the sales and the installation side. Our sales representative was very accommodating and helpful. The installation crew was efficient and they all were professional. These are really nice windows and a great upgrade especially from builder-grade windows."

Brad Allen
Nov 17, 2022

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1speedwagon
Nov 17, 2022

"Everyone I worked with from setting up the initial appointment to the salesman to the installers to everyone who checked on us and kept us updated on the progress of the windows was courteous, professional, and responsive. There’s always someone who is willing to answer your question without jumping through hoops which is rare these days! The installers were on time, did a beautiful job, cleaned up the space better than I expected, and even helped me with some blinds I couldn’t remove and fixed my squeaky front door! I’ve already recommended Renewal by Anderson to friends!"

Karen Mortillaro
Nov 19, 2022

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