The heating is on for the first winter in your new build, and the radiator under the living room window is about to meet the floor-length curtains you have had open in a browser tab for a fortnight. One of them has to give, and it will not be the radiator.
So, should curtains cover a radiator? Not while it is on. A curtain closed over a radiator heats the window. That does not mean settling for short curtains, or giving up the look you had in mind. It means deciding which layer at the window does the work and which one is there to look right, and letting the radiator decide the rest.
Why the radiator is under the window
Radiators went under windows when windows were single glazed and let the cold in. Cold air fell off the glass, the radiator warmed it on the way down, and the room avoided a cold patch by the window. Double glazing has taken most of that problem away, and heating firms will now tell you there is much more choice about where a radiator goes.
If yours is still under the window, it is there for reasons that hold up. Glass is still the coolest surface in the room. And the wall under a window is the one stretch of wall nothing else wants. Nothing tall can stand there without blocking the light, and every other wall already has a job. The best one in the room usually has three things competing for it. The radiator is in the right place. The curtains are the thing that has to fit around it.
What a curtain does to a radiator
A radiator heats a room by warming the air next to it, which rises and pulls cooler air in underneath. Close a floor-length curtain over it and you have built a chimney. The warm air goes up the gap between the fabric and the glass and spends itself on the window, and the room on the other side of the curtain gets what is left.
The valve makes it worse. The thermostatic head on the end of the radiator reads the air around it, and behind a curtain that air is warm. So it decides the room is up to temperature and turns the radiator down, while the room is not.
If the house has an air source heat pump, there is a second problem, and it is physical. A heat pump sends water round at roughly 35 to 45°C, against the 75°C or so a gas boiler works with, so its radiators need more surface to put the same heat into the room. More surface tends to mean double or triple panel radiators, which are deeper and stand further off the wall. A floor-length curtain hung over one has to bend round it to reach the floor, and it will lean on it all winter.
Four ways to dress that window
A blind in the recess, and nothing else
A Roman or roller blind fitted inside the window recess comes down to the sill and stops, so the radiator underneath is never covered. It does the privacy and the dark, and a lined Roman blind takes the chill off the glass at night. It needs enough depth in the recess to clear the window handles on its way down, which is the first thing to measure.
This is the right answer in a bedroom with a short window, and anywhere the wall either side of the window is too narrow to take curtains. It is the least you can do to a window, and in the right room it is all the window needs.
Curtains that stop above the radiator
Curtains can close and still leave the radiator alone, as long as they stop short of it. The hem finishes below the sill and clear of the top of the radiator, so the curtains cover the glass and the heat rises into the room rather than behind the fabric. You get curtains you can close at night without giving the heat away.
It is also the arrangement most likely to look wrong. A curtain that stops halfway down a wall can look as though it has shrunk in the wash. It needs a pole that runs well wide of the window, so the curtains stack on the wall rather than across the glass, and a fabric with the weight to hang straight to the hem: a lined linen or a cotton velvet, not a voile.
A blind that works, and curtains that never close
In a living room, this is the one to beat. A blind in the recess does the work: privacy, light and the dark. Floor-length curtains hang either side on a pole that runs wide of the window, and they stay open. They are there for height and softness, and because they never close over the radiator, they never cost you any heat. The trade calls them dress curtains.
They need less fabric than curtains that close, because they only have to cover the wall either side of the window rather than the window itself. That frees you to choose a heavier fabric or a bolder pattern than you would risk across a whole window. In a new build they do one more job. An empty house echoes until there is enough fabric in it, and a pair of floor-length curtains is a lot of fabric on one wall, open or closed.
Floor-length curtains that close anyway
You can have floor-length curtains that close over a radiator, on one condition: they stay open while the heating is on, which on a November evening is most of the evening. Tiebacks hold them clear of it in the meantime.
If the curtains are already made and too long, tucking the hem behind the radiator keeps its front clear, which is what Eastside Community Trust's guide to keeping the heat in suggests. It works. It also looks like what it is.
Measure the radiator as well as the window
Most of what goes wrong with this window goes wrong at the tape measure, before anything is ordered. Three measurements decide which of the four arrangements will work.
The depth of the window recess, which tells you whether a blind can drop clear of the handles.
The gap between the sill and the top of the radiator, which tells you whether a curtain can finish inside it without looking stunted.
The width of wall either side of the window, which tells you whether curtains can stack off the glass or will sit across it all day.
Window treatments are the part of a house most often left until last and most often got wrong. That is why made to measure curtains and blinds, specified and installed, are part of what we do as interior designers in Bristol, and in Bath, Keynsham, Portishead and the towns around them. If your windows are still bare, start with The Windows Are Bare, And That Is Normal. If you are still working out what came with the house, Do New Builds Come With Blinds? answers that first.
Before you order the curtains
Design Seven is a Bristol studio. Most of our work is show homes for housebuilders, which means we furnish empty new builds for a living. We take on private projects too, whether that is a single room, a whole house, or curtains, blinds and lighting measured and fitted properly. We are based between Bristol and Bath, and work across the South West and further afield where the project warrants it.
Stand in the doorway, take one photo from there, and send it to us. Add the three measurements: the depth of the window recess, the gap between the sill and the top of the radiator, and the width of wall either side of the window.
We will tell you which of the four arrangements that window wants, how wide the pole should run, and whether the curtains in that browser tab can work there. Whatever the answer, it starts in the same place. The radiator got there first, so the radiator decides how long the curtains can be.
Call 0117 450 6707, email info@designseven.co.uk, or use the form on our contact page.