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What are transom windows?

Casement windows, skylights, sliding windows, bays, sash windows, awning windows, gables, bows, dormers, fanlights, transoms. All are different, and all have their own distinctive styles, features and uses. And of course all allow light to pass through, that being the primary and original purpose of a window when all’s said and done.

But the transom window also has another unique traditional function, more about which later on. First, we need to clarify that a transom is a beam that goes across the top of a door to separate the door itself from an area of glass above it. The beam and the glass above it together create a transom window.

Is that all a transom window is?

Not at all. Also known as transom lights or just transoms, transom windows are most commonly positioned horizontally above not just exterior doors but interior doors as well, and even above other windows, to let in more light.

You can have rectangular transom windows above doors to match with the width of the door – which might also have glazed panels on one or both sides, known as sidelites – or you can have transom windows arched into a series of glass panes that are fanned out. This brings us to our next point.

Is a transom window the same as a fanlight window?

No. A fanlight only lets in light and is usually more of a decorative feature window than one with a practical use. What’s more, fanlight windows are usually made with coloured glass and are often arranged in a sunburst pattern. But a transom window, as hinted at above, has a unique traditional function besides the usual one of letting in light. 

So, what’s unique about a transom window?

Traditionally, transom windows had two functions. Rather than simply allowing light into inner rooms, the transom window opened above the door not only to act as a form of air conditioning, but to create draw from a fireplace to move warmth to upstairs rooms. Then in summer, the front and back transom windows could be opened so air could circulation to keep the house cool.

With today’s modern central heating systems, and indoor air conditioning, the drawing and ventilation aspect of transom windows is not needed as it once was. On the other hand, a transom window can both add charm and elegance to your entryway, and allow more natural light into your interior living space.

The Residence Collection

Should you like the idea of a transom window, but live in an area where new windows and doors may need planning permission, you’ll be pleased to know that at The Residence Collection we have a network of trusted installers with expertise and experience in period properties, including statement installations such as transom windows.

Download one of our brochures or find your local Residence Collection installer using our handy search tool.



At Residence Collection, we have a range of colours available and can offer everything from timeless classics like Grained White to modern favourites such as Eclectic Grey. Don’t forget, we also offer a dual finish that allows you to find windows and doors that look as good from the inside as they do outside.