Why Radiators Were Traditionally Fitted Under Windows

In many older UK homes, radiators were fitted under windows because windows were often the coldest part of the room.

Before modern double glazing and better insulation, a radiator under the window helped warm the cold air coming from the glass and encouraged warm air to circulate around the room.

That is why so many bay windows still have a radiator directly underneath them.

In modern homes, or older homes that have been upgraded with double glazing and insulation, this issue is often not as important as it once was. That is one reason radiators are now often fitted in different positions.

Does Covering a Radiator with Curtains Really Matter?

It can matter, but it depends on the room and how you use it.

If floor-length curtains cover a radiator, some heat may be trapped behind the fabric instead of flowing freely into the room.

But in many modern homes, the effect may be less dramatic than people expect, especially if the windows are double glazed and the room is already reasonably well insulated.

It also depends how you use the curtains. In a living room, for example, many people keep blinds closed first and leave the curtains open until later in the evening. The curtains are then drawn mainly to make the room feel softer and more cosy.

In bedrooms, some people prefer not to keep the heating on late into the evening anyway, because they do not want the room too warm while sleeping.

Option 1: Short Curtains Above the Radiator

If keeping the radiator completely clear is your priority, short curtains are usually the safest choice.

These curtains normally stop at the top of the window sill, with the track fitted closer to the window within the bay.

This keeps the radiator fully open and allows heat to circulate into the room without the curtains covering it.

The trade-off is that sill-length curtains can look more practical and understated than floor-length curtains. They can work very well, but they do not usually create the same soft, full curtain look.

Option 2: Curtains Just Below the Sill and Above the Radiator

This is a very common setup in UK bay windows.

The curtains hang in front of the sill and drop just a few centimetres past it, often stopping just above the radiator.

This gives a softer look than curtains that stop on top of the sill, while still avoiding most of the heat loss concerns that come with covering the radiator.

In this situation, the curtain track normally sits just in front of the sill and is usually ceiling fixed.

For many rooms, this is the best compromise between appearance and practicality.

Option 3: Floor-Length Curtains Over a Radiator

Floor-length curtains usually give the most generous and decorative finish in a bay window.

They can make the bay feel taller, softer, and more complete, especially when the curtain track returns out of the bay and onto the side walls.

The downside is that if the radiator is directly below the bay, the curtains may cover it when closed.

For some people, this is not a big issue. If the room is already warm enough, the radiator is not used heavily, or the curtains are only drawn later in the evening, floor-length curtains may still be the preferred choice.

For others, keeping the radiator clear will matter more than the look of long curtains. This is where you need to decide which compromise suits your home best.

Renovating? Think About the Radiator Before Choosing Curtains

If you are renovating, decorating, or changing the heating layout, it is worth thinking about your curtains before the radiator is fitted.

More people are now moving radiators away from the bay window and fitting tall radiators on the return walls instead.

This can be a great solution because it leaves the bay clear for floor-length curtains. But it can create a new problem if the radiator is fitted too close to the bay corners.

Ideally, leave around 20cm to 25cm of clear wall space near the bay corner so the curtain track can return onto the wall and the curtains have somewhere to sit when open.

Be Careful with Chunky Radiators in Bay Windows

Chunkier style radiators can look great, but they can be awkward when fitted inside a bay window.

If a radiator projects a long way out from the wall, the curtains may need to hang much further forward to avoid draping over it.

This can affect where the curtain track sits and may make the whole bay window layout more difficult.

If you are choosing a chunky radiator for a bay, I usually prefer floor-standing radiators where possible rather than bulky wall brackets.

If a wall bracket is needed to stabilise the radiator, using one central bracket can sometimes be better than having brackets at each side, as long as this is suitable and safely fitted by your heating engineer.

A Useful Renovation Tip

If you are fitting a radiator below the bay window and you want floor-length curtains, one option is to position the radiator slightly forward from the wall.

Leaving around 15cm to 20cm behind the radiator can allow the curtains to close behind it rather than in front of it.

This can reduce the heat-loss issue while still allowing you to have long curtains in the bay.

This kind of detail needs to be planned before the radiator is fitted, but it can make a big difference to how the finished room works.

Still Not Sure Which Option Is Best?

Start by deciding what matters most to you: keeping heat flowing freely into the room, getting the softest curtain look, or finding a sensible balance between the two.

Once you know that, it becomes much easier to choose between sill-length curtains, just-below-sill curtains, or full floor-length curtains.

Frequently asked questions