Mint front door interior with transom window and sidelights

What are transom windows? An old design style has new charm

Jerica Pender Contributing Writer

Jerica Pender is a contributing writer for USA TODAY Homefront. She’s written about mold prevention strategies, what to do with an unused fireplace, how to reduce plastics in the home and how to make small spaces work for families. Jerica’s work has been published in the Washington Post and various regional publications. When Jerica is not writing, she swings a hammer to remodel her Olympia, Washington, home. She loves to travel to national parks with her family and hopes to visit them all.

Updated Jul. 1, 2024

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Key points

Transom windows can enhance a home’s aesthetics and complement its architectural style.
Though now uncommon, some transom windows can open to increase airflow and ventilation.
These windows have many applications because of their shape, size and material options.

If light streaming through rectangular glass above a door — or a frosty-paned semicircle smartly positioned above another window — reminds you of yesteryear, it’s for good reason: Transom windows have been around since at least the 14th century.

These compact windows serve many style and functional purposes, from adding natural light and airflow to creating grandeur and affording privacy. A transom window, commonly installed above a door transom, is an old design style that’s seeing new favor.

Read on to find out if a transom window would suit you and your home.

What’s the purpose of a transom window?

Joshua Williams, sales coordinator for Acadian Windows, a window manufacturing and sales company in New Orleans, explained transom windows were “originally a function design.”

“Before we had central heating and cooling, they’d be put at the top of the front and back doors and you’d be able to open them up and air would travel through. Nowadays, they’re [usually] not functional and more of a design aesthetic,” he said.

Aesthetics

Transom windows, or transom lights, as they’re often called, vary by shape, pane type and frame color. The myriad design options available can easily enhance your home’s architectural style. You’ll find them either single- or multipaned, rectangular or curved, and made of clear glass panes or frosted.

Rectangular transom windows are often paired with sidelights. *Jason, Adobe Stock*

Transom windows can make a standard window installation more impressive. Although modern window manufacturing capabilities are quite sophisticated, there are still manufacturing size constraints, said Williams.

If you have a taller ceiling height or are looking to maximize your view, “You can add a transom and it’s going to give you that big, full view,” he said. “It makes those [standard] windows look bigger and it looks nicer from an aesthetic standpoint.”

Entryway transom windows made from stained glass were popularized in Victorian times, but this type of transom window still enchants and delights homeowners. When the morning or evening light hits a stained-glass transom just right, it can wash a room aglow.

Transom windows can also be found in Georgian architecture (1714–1830) and Colonial Revival (1880–1955). You’ll often see them in modern homes and lodges.

Energy efficiency

It’s not just style choices that have transom windows trending; energy efficiency and airflow also pique interest. Adding south-facing transom windows can help warm up homes in colder climates, and both interior transom windows and exterior transom windows draw additional light into your space.

Transom windows are commonly found as part of a “mulled unit,” where sidelights (tall and narrow windows) flank each side of a door, and a transom window spans the top of the door and sidelights to create a bright and impactful entryway, according to Williams.

Aside from their decorative purposes, mulled units boost energy efficiency because you can make one big opening, and the mulled unit slides in. Williams added that transom windows are no different from other windows in that the most important thing is a proper installation where everything is well-sealed.

Ventilation

Operable transom windows, or awning windows, often require additional hardware and manufacturing. Although they’re not today’s standard, paying the extra cost for transom windows that open provides a huge benefit when it comes to ventilating your space.

Consider your climate when determining whether your transom window should be operable or remain fixed. Williams said it’s unheard of not to have air conditioning in the Southern United States where he lives, but in places such as the Pacific Northwest where indoor cooling is only needed a few short weeks per year, air conditioning is not the norm. In those cases, the added ventilation from an operable transom window makes a lot of sense.

You should also consider a room’s function. Because of their small size — the average transom window is 3 feet by 1 foot — they can be installed in a variety of places and are especially useful when square footage is tight, the roof is low or there are existing utilities in the wall, such as plumbing or electric.

I am in the process of adding a bathroom to my home and installed two vinyl transom sliders above the vanity because that’s the only window type I could fit, and the room was desperate for more light and ventilation.

What are the types of transom windows?

Transom windows range in shape and size, and the frames can be constructed from various materials.

Styles

Transom windows come in three main styles. A semicircular window or half-round comprises separate panes that fan out and are sometimes referred to as fanlights. Arched transom windows are curved at the top with straight sides. Lastly, there are rectangular transom windows.

Semicircular transom windows are often made of individual panes that fan out. *Dolores Harvey, Adobe Stock*

Sizes

Williams said the transom window size you select is usually determined by where it’s being installed. For example, many windows are 36 inches wide, so the transom would match that.

He added that the most common transom window heights are 12, 16 or 18 inches. They can go up to 24 inches tall, though this is uncommon.

Materials

Transom windows can be made of the following frame materials:

Vinyl (most common and cost-effective)
Aluminum (a wood frame with aluminum cladding, or covering)
Fiberglass (a wood frame with fiberglass cladding)
Wood frame

Where should you install transom windows?

You should install a transom window anywhere you need additional light, ventilation or aesthetics. This versatile window can be installed on exterior or interior walls — the latter allows more natural light to flow throughout the home while maintaining a room’s privacy.

What is the installation process like?

Window installation is a multistep process that draws upon various skills such as framing, sheeting and finishing work. Generally, window installation is not a good DIY project for the average homeowner.

Professional installation vs. DIY

Pay attention to water-tightness and leaks when adding or replacing a window. Not only does a poor installation negatively impact energy efficiency, but it will often lead to leaks, sometimes unbeknownst to homeowners. Poor installations can cost you financially and lead to rotted materials, mold growth and potential health issues, Williams explained.

“I highly recommend hiring a professional to make sure it’s done right, flashed right and has the right type of trim installed on the facade,” said Williams.

What’s next?

Exploring your options with transom windows can be a fun, albeit overwhelming, process that includes narrowing down the style, material and function that’s right for your home.

Schedule at least three consultations with window professionals, and consider working with one of our best window brands. Be sure to get bids on the total costs, as you will need to factor in both window and labor costs.

Transom window designs can take you on an architectural journey through the eras. Whether Tudor, Victorian, Gothic, Arts and Crafts, or Craftsman, there’s a transom window design out there to complement the style that suits you best.

Editorial note: The name “Homefront” refers to the alliance between USA TODAY and Home Solutions that publishes review, comparison, and informational articles designed to help USA TODAY readers make smarter purchasing and investment decisions about their home. Under the alliance, Homefront provides and publishes research and articles about home service and home improvement topics.

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Jerica Pender, Contributing Writer Homefront

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Erika Skorstad, Editor Homefront

Learn more about Erika Skorstad

Erika Skorstad is an editor for USA TODAY Homefront. She covers topics ranging from home warranties to lawn care. Previously, Erika edited content about venture capital, marketing and cloud computing. She has a BS in professional writing with a minor in interactive narrative. Her fiction has been published in Marathon Literary Review, Levitate Literary Magazine and the Burlington Writers Workshop Cold Lake Anthology. Outside of work, Erika enjoys reading psychological thrillers, doing yoga, going on nature walks and spending time with her sassy black cat, Cassie. She lives in Washington.

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