The one curtain mistake that makes rooms feel icy: heating advisors explain how to hang them so radiators actually work

On a January evening it’s the tiny rituals that keep you going. The clunk of the timer as the heating comes on, the soft rush in the pipes, the promise that in twenty minutes you won’t need to keep your shoulders hunched inside your dressing gown. You close the curtains, flick on a lamp, and wait for the room to exhale.

Except sometimes it doesn’t. The boiler has definitely fired, the radiators feel hot if you rest a hand on them, yet the air hovering at sofa height stays stubbornly chilly. You turn the thermostat up a notch, then another, and tell yourself the house “just takes a while to warm through”.

Heating advisors will quietly tell you: in a huge number of British homes, the problem isn’t the boiler at all. It’s the curtains. Not the fact that you have them, but the way they’re hung - a single, very common mistake that can trap heat in all the wrong places and leave you paying for warmth you never feel.

Once you’ve seen it, you can’t unsee it. A thick wave of fabric sweeping right across a radiator. A curtain tucked behind the panel “to keep it neat”. A floor-length drape in front of a convector grille, billowing gently as your gas bill rises. Cosy to look at, icy to live in.

The cosy-looking habit that quietly cools your home

Ask any home energy advisor what they notice first on a visit, and many will say the same thing: curtains swallowing radiators whole.

You see it in terraces and new-build flats alike. Radiators are often fitted directly under windows, because that’s where the coldest air tends to fall. Then, when someone moves in, they hang a generous pair of curtains that run from above the window right down past the sill and across the front of the radiator. In the evening, they draw them fully. The heat source is now on the wrong side of a fabric wall.

From the sofa, the scene looks snug. From a physics point of view, it’s perverse. The radiator keeps churning out warmth, but instead of spilling into the room, hot air rises behind the curtain, hits the cold glass and the top of the recess, then loops back down in the narrow gap. The glass warms, the outside world warms a little, and you do not.

“It’s one of the simplest fixes we see, and one of the most common problems,” as one advisor summed it up. “People are essentially heating the back of their curtains and the window pane, not the room they’re sitting in.”

What radiators actually need to work

A radiator doesn’t just radiate. In most modern systems it does two jobs at once.

Part of the heat is radiated directly into the room - you feel this as a gentle glow if you stand in front of it. But a big share comes from convection: cool air near the floor brushes past the hot metal, warms up, becomes lighter and rises. That rising column of warm air spills into the room, pulling more cool air in behind it. Left undisturbed, this quiet loop gradually takes the chill off.

When you drop a curtain in front of the panel, especially a thick, lined one that reaches below the sill, you interrupt that loop. The “mini climate” between radiator and fabric can be several degrees warmer than the room, but the heat is largely trapped. If the curtain touches the top of the radiator or hangs in front of the grille, the escape route for warm air is almost completely blocked.

A similar thing happens if you tuck curtains behind the radiator. It looks tidier and stops them covering sockets, but the fabric now acts like a blanket on the panel. The metal gets very hot, the water returning to the boiler is warmer than it should be, and the heating system thinks it’s done more work than it has. The room remains cool, the boiler cycles off sooner, and you’re left wondering why “the heating’s useless”.

In short: radiators need clear space above and in front of them to do their job properly. Anything that cages them in - however stylish - costs you comfort first and money soon after.

Spot the curtain mistake in your own rooms

You don’t need a thermal camera to see whether your curtains are sabotaging your heating. A two-minute walk round the house will usually tell you enough.

Look for:

• Curtains that fall across the front of a radiator when drawn, especially if they’re heavy or interlined.
• Fabric resting on or very close to the top grille of a convector-style radiator.
• Drapes tucked behind the panel to “make the window look bigger” or keep them out of the way.
• Poles or tracks fixed far above and beyond the window, so that when closed the curtains cover both glass and radiator in a single sweep.
• Bay windows where the centre radiator is entirely hidden by a continuous run of curtains in the evening.

Then pay attention to how those rooms feel in use:

• Are your feet or ankles often cold even though the radiator feels very hot to the touch?
• Do you crank the thermostat up in the rooms with the longest curtains?
• Does the area behind the curtain feel almost stuffy when you reach in?

If the answer to any of these is yes, you’ve probably found an easy win.

How to hang curtains so your radiators can breathe

Heating specialists don’t want you to live with bare windows; good curtains are still one of the easiest ways to cut draughts and reduce heat loss. The trick is to let them work with the radiator, not against it.

Here’s what they tend to recommend.

1. Stop the fabric at the sill (or just below)

If you have a radiator under a window:

• Aim for sill-length curtains, finishing roughly 1–2 cm above the radiator or the windowsill if it sits just above the panel.
• Avoid designs that drop down to the floor in front of the radiator - save those for windows without heat sources below.
• If your existing curtains are long, consider having them re-hemmed to clear the radiator. It’s an inexpensive alteration and can pay back in both comfort and energy use.

For deep sills that jut out over the radiator, the key is that the curtain seals to the sill, not past it. That way, cold falling air from the glass is blocked, but warm air from the radiator can still spill out into the room.

2. Keep a gap above the radiator

Radiators need a little headroom:

• Leave at least 8–10 cm between the top of the radiator and the bottom of the curtain when it’s drawn.
• If you’re fitting new poles or tracks, position them so that, when closed, the curtain hangs clear of the grille rather than resting on it.
• Where the pole is already high and can’t be moved (for example, in a rental), use tie-backs in the evening so the curtain arches away from the panel instead of clinging to it.

Think of it as creating a slot for warm air to escape. Even a visible band of radiator below the curtains is enough for that convection loop to form properly.

3. Avoid tucking curtains behind radiators

It’s a habit many of us picked up in childhood homes, but advisors wince when they see it.

Better options:

• Use shorter curtains that sit fully above the radiator.
• Fit holdbacks or magnetic tie-backs to pull fabric away from either side of the panel without pushing it behind.
• If space is very tight, consider replacing curtains with a blind plus side dress curtains that stop at the sill and never meet the radiator at all.

The aim is always the same: the radiator should be able to “see” the room, not just a wall of fabric.

4. Choose the right treatment for each window

Different setups call for different solutions:

• Radiator under a standard window
  Sill-length curtains or a well-fitted Roman blind with short side curtains that don’t cover the radiator.

• Tall window or French doors with a radiator nearby
  Full-length curtains are fine if the radiator is to the side and not directly behind the fabric when closed. If it is, think about a shorter panel just in front of the radiator and a full-length one on the opposite side.

• Bay window with a central radiator
  Instead of one long run of curtains, use separate drops for each section of the bay, or opt for bay-shaped tracks that let curtains sit just in front of glass, not the radiator.

When in doubt, the simple test is this: close the curtains and then look back from the middle of the room. If you can’t see the radiator at all, it’s probably working harder than it needs to for the comfort you get.

Small fixes if you can’t change the pole or curtains

Not everyone can start again with new tracks and beautifully tailored drops. If you’re renting, or you’ve only just bought the curtains, there are still ways to help the heat out into the room.

• Use tie-backs at radiator height
  In the evenings, pull the curtains in so they cover the glass but fit snugly to the window reveal, not drifting across the radiator. A simple tie-back can pinch them in at sill level and create a chimney for warm air to rise into the room.

• Add a discreet clip or hook
  Small command hooks on the wall just above the radiator can catch the curtain edge and keep it forward, leaving a gap behind for air to circulate.

• Lift the hem temporarily
  Iron-on hemming tape can bring a curtain up a few centimetres for the winter without committing to permanent alterations.

• Pair a blind with partially open curtains
  Let a thermal blind do the heavy draught work, then pull curtains in only part-way in the evening so they frame rather than smother the radiator.

None of these are perfect, but even partial clearance can make a noticeable difference to how quickly a room feels warm once the heating comes on.

How much difference does it really make?

Energy modellers talk in percentages; householders talk in feelings. On both measures, the way curtains meet radiators matters more than you might expect.

Advisors who use thermal cameras often see temperature differences of 3–6°C between the air trapped behind a curtain and the rest of the room when a radiator is covered. That’s warmth you’ve paid for but can’t sit in.

The old rule of thumb is that each 1°C drop in thermostat setting can shave around 5–10% off heating bills. If blocked radiators mean you’re setting the thermostat two degrees higher than you really need to feel comfortable, you’re paying extra every single hour the system runs.

You also wear the house out faster. Radiators running hotter than necessary, boilers cycling more often, rooms that never quite dry out - all of it adds up over a winter. By contrast, when heat can move freely:

• Rooms reach a comfortable temperature faster.
• The thermostat can be set lower without feeling spartan.
• The boiler runs in longer, steadier cycles, which most models prefer.

None of this requires smart tech or expensive kit. It’s a tape measure, a step ladder, and perhaps a quiet afternoon with a sewing box or local curtain maker.

Here’s a rough snapshot of common setups:

Curtain + radiator setup	Effect on warmth in room	Easy improvement
Long curtains fully covering radiator when closed	Slow to warm, cold at ankle level	Re-hem to sill length; use tie-backs
Curtains tucked behind radiator	Radiator hot, room still cool	Bring fabric in front; shorten drop
Sill-length curtains clearing radiator by 1–2 cm	Good warmth, fewer draughts	Add thermal lining if needed

A simple evening habit that helps

The other small change advisors swear by isn’t really about curtains at all; it’s about timing.

• Daytime: open curtains and blinds fully to let any winter sun in and stop moisture building up against cold glass.
• Around dusk: close them to cut draughts and reduce radiant heat loss through the glass - but make sure they don’t now swallow the radiator.
• Before bed: check that radiators aren’t trapped behind furniture as well as fabric. Sofas pushed right up against panels have a similar effect.

It’s domestic choreography, really. You’re giving the heat a clear path from boiler to radiator to the middle of the room where you actually live.

When warmth finally matches what you’re paying for

You notice the change in small ways. The time between the heating clicking on and you loosening your dressing gown shortens. The place on the sofa where you always needed a blanket starts to feel fine with just a jumper. The temptation to nudge the thermostat “just for half an hour” fades a little.

None of that comes from miracles inside the boiler cupboard. It comes from fabric, poles, and a bit of thought about airflow.

If you do one thing this week, stand by the coldest-feeling window in the house at dusk and watch what your curtains are doing to the radiator below. If they’re hugging it like a winter coat, that’s your sign. Lift them, shorten them, tie them back - whatever your home allows.

You might not be able to change the price of gas, but you can at least make sure the heat you’re buying ends up in the room with you, not sulking behind a beautifully hung curtain.

FAQ:

• Do I have to get rid of my heavy, lined curtains to stay warm?
  No. Thick, lined curtains are excellent for reducing heat loss through glass. The key is how long they are and where they fall. If they’re trapping the radiator, have them shortened to sill length above the panel, or use tie-backs and clever positioning so they insulate the window without covering the heat source.
• Are blinds better than curtains if I’ve got radiators under my windows?
  For many under-window radiators, a well-fitted blind (especially a thermal one) paired with shorter side curtains is a very effective setup. The blind stops draughts at the glass, while the radiator is left free to heat the room. Just avoid bulky Roman blinds that sit directly in front of a wall-mounted radiator when lowered.
• Do radiator covers cause the same problem as long curtains?
  They can, if they fully box in the panel without decent gaps at the top and front. A well-designed cover with a generous grille on top and slats at the front can still allow convection, but anything that turns the radiator into a sealed cupboard will cut its output. If you already have covers, make sure there’s a clear exit route for warm air and keep fabric away from the openings.