Muntin vs. Mullion: What is the Difference? 

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Greetings homeowners! It is time to acquaint you with some architectural terminology that will be very helpful to you – especially if you are working on any external remodeling projects! 

What we want to introduce to you is muntin and mullion – both of which are a part of the door and window system. They each have distinct roles and were created for particular uses, so you must understand the differences!

Keep on reading to understand the difference between muntin vs mullion, as well as learn more about their specific uses, purposes, and everything else there is to know about them!

What is a Muntin? 

The upright dividers that split the glass panels in a window are referred to as muntin. It only pertains to the frame’s inner vertical elements – the stiles and rails make up the frame’s exterior pieces.

Although traditionally constructed from wood, some are now made of steel.

Some window grills are fake muntins, which means they have the same appearance as muntins but do not divide the individual panes of glass. Instead, they fasten to a single, large piece of glass. This is typically found on newer buildings since it offers the same attractiveness as muntins without running the risk of creating a draft.

Larger pieces of glass, on the other hand, can be challenging to install and move to the location without damaging them, making muntins the more practical option. Since wide window panes without muntins are frequently saved for workplaces and storefront displays, muntins can lend a sense of comfort to a home.

On the other hand, we’ve seen several stunning contemporary homes without muntins, and in some circumstances, we even advise doing so to give your house an instantly modern vibe. 

Let’s look at some of the muntin applications before discussing the difference between a muntin versus a mullion.

Muntin Application 

Regardless of the neighborhood’s preference for a particular architectural style, you’ll probably see muntins on almost every house. Of course, traditional windows will have most of them. However, they can also be found on garage doors and front doors in some cases.

The grid with equal sides is the classic muntin pattern. Glass panes occasionally appear as squares, although more often than not, they are rectangles. Muntins, on the other hand, can create a lovely arching design on windows in the church style.

What is a Mullion?

two mullioned windows

All that matters when attempting to distinguish between muntin versus mullion is what they divide! Muntins divide glass panes, whereas mullions separate two or more adjacent windows or door frames. Mullions can move both horizontally and vertically.

Mullions have numerous uses. For instance, they can separate a group of fixed windows from a set of movable windows, making it simple to let a cool breeze into your house. In addition to adding depth to resist wind stress, these components are also very important in areas that are vulnerable to hurricanes.

The Main Distinction Between Muntin vs. Mullion 

We already discussed what muntins and mullions are, so let’s now look at how the two differ in terms of architecture and their intended uses.


Muntins, which can be made out of metal or wood, are vertical dividers that split glass panels in a window. These tiny grilles cut large glass panes into smaller pieces.

The strong separating bars, on the other hand, that tie two windows or doors together are known as mullions. They can be either horizontal or vertical in orientation. This is the primary difference between muntins vs. mullions when it comes to architecture. 


As we already mentioned, muntins are used to support the glass and split the window into individual lights. They are employed to separate one large window into a grid of tiny glass panes known as lights. 

Mullions, on the other hand, act as casings to separate the panes of a window or door. Consider installing three twofold sash window units adjacent to each other to create one large window in an area with a beautiful view. To keep the glass pieces together, you’ll need to insert supporting elements in the spaces between them – mullions. 

Muntin vs. Mullion – Maintaining Elegance

Design, color, and material all matter when putting muntins and mullions on your property! 

When it comes to color, choosing the right one for your muntins and mullions can have a significant impact on your exterior remodeling project as decorative elements. As a general principle, make sure your muntin contrasts nicely with the exterior surface color scheme of your property.

Even though a mullion typically appears best when it complements the color scheme of the rest of the house, it can also look fine when it complements the window frame.

Once you’ve decided on the ideal hue, selecting the desired material is simple. For muntin, wood is the classic material, however, for a mullion, tougher components like steel are an excellent choice.

When it comes to shape, mullions are typically just a straight line, whereas muntins come in a variety of shapes.

Nearly all window designs, including transom and western-style windows, feature muntins, and mullions. They can be used on any window form – from a circular to a perfect square. 

Including these components in your home is a wonderful way to express your personality via the small details and combine beauty and utility.

Muntin vs Mullion – Final Thoughts

So, what is the difference between muntin vs. mullion? Despite the frequent confusion between the terms muntins and mullions, it is not very hard to distinguish between the two.

Mullions can be found in both door frames and window panels, while muntins are typically only utilized in windows. Mullions can stand either horizontally or vertically, whereas muntins are narrow upright grilles that cut glass windows into smaller sections.

Now that you understand the differences between muntin vs. mullion, we wish you luck in choosing the ones that will best suit your house! 

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