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Key Differences Between Window Mullions and Muntins

Mullions and muntins are components of your windows that you might not have heard about. But even if you have, chances are that you can confuse them for each other. In this blog, top double-hung windows installer, Renewal by Andersen® of Atlanta, shares the key differences between window mullions and muntins, plus their functions.

Key Differences Between Window Mullions and Muntins

What Purpose Do They Serve?

Window companies rarely discuss muntins and mullions since they are often overlooked and their differences are usually too subtle for customers to notice. Over the years, muntins and mullions have evolved thanks to innovative designs and research, and resulted in the product which we know today which are window grilles. Muntins and mullions work in tandem to support your windows and give them more stability. Nowadays, grilles are used as an aesthetic and security feature for windows. Keep in mind that not all windows come with grilles as they are offered as an accessory.


Muntins are a vertical divider that are commonly used in windows installation projects, as well as panels, and doors. Back then, muntins were used to support the heavy weight of large windows along the walls which let the weight be distributed vertically. Otherwise, the window could collapse due to a lack of balance or a support structure.


While mullions serve as a support structure for windows like muntins, mullions are used to join small windows to create a faux large window since creating large glass panes weren’t possible during the pre-Victorian era when they were primarily used. 

Even though mullions and muntins do not serve any functional purposes in windows nowadays, their functions back then helped pave the way to creating the more stable and secure windows which we use today.

Looking for the highest quality of casement windows? Call on Renewal by Andersen of Atlanta! We offer the best windows and doors on the market today. You can trust our skilled contractors as they will do their best to find the best materials that will work for your home and budget. Call us at (404) 491-0124 or fill out our contact form to get in touch with us. We serve clients in Atlanta and greater GA.


"Awesome job! Everything was completed as communicated. Everyone was very courteous and friendly. Other contractors should follow the Renewal by Andersen footprint."

Richard & Camille, Lawrenceville GA January 22
May 25, 2016

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