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Transom Windows: Small Panes With a Big Design Payoff

Walk into an older home with tall ceilings and there’s a good chance a small, wide window sits quietly above the front door or between two rooms, doing more work than its size suggests. That’s a transom window, and it’s one of the few architectural details that manages to be both practical and decorative at the same time. Homeowners renovating older properties, and even those building new, keep circling back to the style once they see what it actually does for a room. Here’s what a transom window is, where it earns its keep, and what to weigh before adding one.

What Is a Transom Window, Exactly?

A transom window is a smaller window positioned above a door, another window, or sometimes a wide opening between two interior rooms. The name comes from “transom,” the horizontal bar that separates the window from whatever sits below it. Transom windows can be fixed in place or built to open, and they come in rectangular, arched, or fanlight shapes depending on the era and style of the home.

Their original job was practical: before mechanical ventilation and reliable electric lighting, a transom window let hallways and interior rooms borrow light and airflow from adjoining spaces. That function has faded, but the visual payoff hasn’t. A well-placed transom window still does what it always did: it stretches a doorway taller, fills a room with extra daylight, and adds a detail that reads as custom rather than builder-grade.

Where Transom Windows Make the Biggest Impact

Not every doorway needs one, but a few spots consistently make the case for adding a transom window.

Above a front entry door, where it draws the eye upward and makes a standard-height doorway feel more substantial
Over interior doors leading into windowless rooms, like a home office or powder room that would otherwise rely entirely on artificial light
Above French doors or patio doors, extending the glass line and making the whole opening feel taller
Between a kitchen and a formal dining room, borrowing light across a shared wall without sacrificing privacy at eye level

Rooms with high ceilings and little natural light are usually the best candidates, since the extra glass sits well above sightlines and does its job without exposing anything the homeowner would rather keep private. A hallway or stairwell that always seems to need a lamp on during the day is often a strong candidate too.

Fixed vs. Operable Transom Windows

Most transom windows installed today are fixed, meaning they don’t open. That keeps the frame slim, the sightlines clean, and the installation simpler, which matters since transoms are often built into tight spaces above a door frame.

An operable transom, usually hinged at the top or bottom, adds ventilation on top of the light. That’s worth considering above an interior door leading into a stuffy room, or over an exterior door where a crack of airflow is useful without opening the main door itself. The trade-off is a slightly bulkier frame and, on exterior installations, one more seal that needs to hold up against Ontario’s weather swings.

Why default to fixed when it’s not needed? Because every operable point in a window system is one more spot that can eventually let in a draft, and a transom that’s rarely opened isn’t worth that long-term maintenance trade.

Do Transom Windows Add Value to a Home?

Natural light is one of the most consistently requested features in home renovation surveys, and a transom window is a low-footprint way to add more of it without cutting a new opening into an exterior wall. For resale, the detail reads as intentional design rather than an afterthought, particularly on a front entry where curb appeal carries real weight.

They’re also a common feature in period-appropriate renovations. A century home missing its original transom above the front door often looks noticeably plainer than its neighbors, and restoring one is a relatively small project with an outsized effect on how the whole facade reads from the street.

Installation Considerations for Ontario Homes

Adding a transom window to an existing opening isn’t purely cosmetic. The wall above the door needs enough structural depth to support a new opening, and on an exterior wall, that means coordinating the header, flashing, and insulation so the new window doesn’t become a cold spot or a leak point once winter arrives. On older Ontario homes with plaster walls or balloon framing, this step matters more than it does in a newer build.

Energy performance matters just as much on a transom as on any full-size window. A poorly sealed transom above a front door can undo a lot of the draft-proofing work done elsewhere in a home, since the small size makes homeowners underestimate how much heat can move through and around a badly fitted frame. It’s worth having a window replacement specialist assess whether an existing transom is actually performing, especially in a home built before energy codes tightened up.

A drafty transom is easy to overlook simply because it’s small and out of reach, right up until the heating bill makes it obvious something up there isn’t sealed the way it should be.

A Small Window That Changes How a Room Feels

Transom windows aren’t a fit for every doorway, but where they work, they do more for a room than their size would suggest: more light, more height, more of that finished, considered look that’s hard to fake with paint or trim alone. If a front entry or an interior doorway has always felt a little flat, it’s worth finding out whether a transom is even structurally possible before ruling it out. That’s a much smaller question to answer now than after a renovation is already finished and the wall is closed back up.

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Frequently Asked Questions

Common questions homeowners ask about transom windows.

What is the purpose of a transom window?

A transom window sits above a door or another window and brings extra natural light and, in some cases, ventilation into a space. Historically it helped hallways and interior rooms borrow light before modern lighting and HVAC systems existed. Today it's used mainly for the architectural detail and the extra daylight it adds above an entryway or interior doorway.

Can a transom window be added to an existing door?

Yes, but it depends on the wall structure above the door. A contractor needs to confirm there's enough header depth and structural support before cutting a new opening, especially on an exterior wall. On interior doors between rooms, the process is usually simpler since there's no insulation or weatherproofing to account for.

Do transom windows let in a draft?

They can, if the frame isn't properly sealed or insulated. Because a transom is small, poor sealing is easy to overlook compared to a full-size window, even though the heat loss adds up the same way. A properly installed and sealed transom performs no differently than any other well-fitted window.

Are transom windows only for older or historic homes?

No. While transoms are strongly associated with older architectural styles, many newer homes use them above front entries, French doors, or interior openings for the same reasons: extra light and a more finished look. The style has never fully gone out of use, it's just less common in standard builder-grade construction.

Do transom windows need to open?

Not necessarily. Most transom windows installed today are fixed, which keeps the frame simpler and reduces long-term maintenance. An operable transom adds ventilation but comes with a bulkier frame and, on exterior walls, an additional seal that needs upkeep over time.

What shapes do transom windows come in?

Rectangular transoms are the most common, but arched, fan-shaped, and multi-pane divided styles all show up depending on the home's architectural period. The shape is usually chosen to match the door or window style directly below it, so the whole opening reads as one cohesive design.

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