Mullioned Windows: A Guide to Window Designs

If you're planning to replace your windows, you've probably come across the term mullioned windows. But what exactly are they? Simply put, mullions are the vertical bars that divide a window into multiple sections. They provide both structural support and serve as a distinct design element.

Are mullioned windows the right choice for your home? They may be, especially if you want to install large windows or French-style casement windows! In this article, we'll break down everything you need to know about mullioned windows so you can decide if they're the perfect fit for your renovation project.

Key Takeaways

• Mullioned windows have vertical bars called mullions that separate large window openings, providing stability and serving as an element of visual interest. French casement windows, for example, are mullioned windows.
• Unlike muntins, which are either vertical or horizontal bars that divide a larger glass pane into smaller glass panes, mullions are larger vertical components that separate large windows into several sections for structural support. Transoms, on the other hand, are horizontal bars above windows or doors.
• If you want to install a large window, it will probably require mullions that offer structural support to the large glazing area. Mullioned windows are also recommended for houses in regions with strong winds and severe weather conditions.
• Mullioned windows are sometimes installed only for decorative purposes, especially in homes with traditional designs.

What Are Mullioned Windows?

Mullioned windows feature vertical bars known as mullions, which separate and support multiple window units. These components ensure structural stability and enhance a window's design. For example, if someone wants a large window installation, they can install multiple mullions that separate a larger glass pane into multiple sections.

Furthermore, mullions can also improve a window's energy efficiency, especially when the mullion separates windows that meet at the mullion. This is because when the window is closed, the sashes are pressed against the mullion, creating an air-tight seal and thus improving insulation.

Mullioned windows have been key architectural elements for centuries. Stone mullions were used even before the 10th century in Armenian, Saxon, and Islamic architecture. The same structural form became highly fashionable across Europe in Romanesque architecture featuring paired windows divided by a mullion that also supported a single arch.

Mullioned windows were also extensively used in Gothic architecture, especially in Gothic cathedrals and churches with window openings necessarily requiring division. They continued to be used during the Renaissance period.

Mullions vs. Transoms

Mullions are vertical bars that separate large sections of a glazing window, providing structural support and aesthetic division.

On the other hand, transoms are horizontal bars positioned above a window or a door. They support smaller transom windows, which are usually installed for aesthetic purposes or enhanced ventilation.

However, you may also hear people using the term mullions for transoms, which is generally accepted in the industry.

Mullions vs. Muntins

Mullions and muntins are frequently confused, but they serve different purposes. Mullions are large vertical bars that separate large panes of glass, providing structural integrity and support. Muntins, however, are very small strips - either vertical or horizontal - that divide a single pane of glass into smaller panes.

Muntins are often referred to as window lites or glazing bars and are primarily decorative. They do not serve the same load-bearing function as mullions. While mullions allow for larger and more stable window installations, muntins create the illusion of divided panes of glass, often mimicking traditional window styles.

Types of Mullions

Vertical mullions are usually integral parts of the frame. This means that if your window has two sashes separated by a mullion, the mullion stays fixed when you open the sashes. You've probably heard of French casement windows, right? They feature this design precisely. French casement windows have two operable sashes separated by a mullion in the center.

However, this design is not too practical. First, it obstructs views when the window is open. Secondly, it can obstruct access, in which case the window cannot be used as an egress window.

So, window manufacturers created something called a flying mullion or a floating mullion. A flying mullion is not an integral part of the frame. Instead, it is attached to one of the sashes and moves with the sash when you open the window. This way, floating mullions allow homeowners to use the window as an escape exit in case of emergencies.

Materials Used in Mullioned Windows

Mullions can be constructed from various materials, each offering distinct advantages and aesthetic qualities.

Traditional wooden mullions, for example, provide a classic aesthetic but require consistent maintenance to prevent damage. For a contemporary touch, homeowners can install aluminum mullions, which are favored for their sleek design and minimal upkeep. Vinyl mullions require little maintenance, which makes them highly practical.

The material used for window mullions is usually the same material that is used for the window frame, especially if the mullions are fixed to the frame.

When to Choose Mullioned Windows

If you want to install large window openings, mullions are a must-have, as they provide the necessary support, ensuring that the glazing remains stable. Plus, they also add a touch of architectural charm - a win-win situation!

Mullioned modern windows aren't installed only for structural support. They are often chosen for traditional or historical buildings, being installed in small windows that would not require a mullion otherwise. In this case, decorative mullions can help maintain the authenticity of various architectural styles and. They are often paired with window muntins.

Last but not least, if you live in an area with strong winds or extreme weather conditions, it's best to install mullioned windows to enhance structural integrity. The added support provided by mullions can help reinforce the window's strength, reducing the risk of flexing or damage in harsh conditions.

Maintenance and Care for Mullioned Windows

Maintenance and care requirements for mullioned windows are basically the same as for any other window type, except that there's one additional component that needs to be taken care of - the mullion, of course!

Dust and debris can easily accumulate around the mullion, especially in crevices where it meets the glazing. It's important to clean it regularly to ensure the sash can be pressed tightly against the mullion if it's operable. Moreover, if the mullion is made of wood, you'll have to make sure you're caring for the wood correctly. If the mullion warps or rots, the window's structural integrity and energy efficiency may be compromised.

In addition to cleaning the mullion itself, it's important to inspect hardware or insulating components, if any. In French-style casement windows, the sashes meet at the mullion, so there's typically a locking mechanism integrated into the mullion. It often includes strike plates or bolts, and the sashes have corresponding locking points that engage with these components on the mullion. Mullions can also have weatherstripping.

Get Your Mullioned Windows with Magic!

Choosing mullioned windows for your home is like giving your space a timeless upgrade. Not only do they bring a unique visual charm, but they also offer functional benefits like added support and improved insulation! Ultimately, mullioned windows offer the advantage to transform a simple window into a statement piece while ensuring your home stands up to the elements!

If you're looking for the best mullioned replacement windows in the GTA, give Magic a call! We are committed to providing you with the best possible solution that is 100% tailored to your unique needs and preferences. One of our specialists will consider your home design, region climate, and budget to ensure that your mullioned windows will be energy-efficient and functional!

Frequently Asked Questions

What are mullioned windows?

Mullioned windows consist of vertical or horizontal bars called mullions, which separate and support several individual window units, enhancing both structural integrity and aesthetic appeal.

What does a mullioned window look like?

A mullioned window has a vertical bar that divides the window unit into several sections. That bar is called a mullion, and it offers structural support and enhances the overall aesthetic of a home. It is commonly used in French-style casement windows to separate two operable sashes.

What is the difference between a muntin and a mullion?

A muntin can be vertical or horizontal and is used to separate a glass pane into smaller pieces for decorative purposes. A mullion is a large vertical bar that divides a window unit equally for structural support.

What is the difference between a mullion and a transom window?

A mullion is a vertical bar that divides a window into two units, while a transom window is a small window installed above a larger window or door.

How do mullions enhance the structural integrity of windows?

Mullions enhance the structural integrity of windows by distributing the weight evenly, which reduces strain on the window frame. This support is crucial for maintaining the durability and stability of large window installations.

What materials are commonly used for mullions?

Mullions are commonly constructed from wood, vinyl, aluminum, and steel, each providing unique benefits and aesthetic appeal. Selecting the appropriate material will depend on your specific design needs and structural requirements.