Interlining. Nobody sees it. Everyone feels it.

The clocks go back this weekend. Dark by teatime from Monday, and this is the time of year people start asking me about cold front rooms.

Very often it isn't the window. It's what's hanging in front of it.

Lined curtains are fine. But if you want a room to feel warmer through the winter, the layer that does the real work is the one nobody ever sees.

Interlining.

It's a soft, blanket-like layer sewn in between the face fabric and the lining. Bump is the thick one, almost like flannel. Domette is lighter, for delicate fabrics or when the curtains need to stack back small.

It changes the whole curtain. They hang heavier. The folds go round and full instead of flat. A silk stops looking thin with the light behind it. The room goes quieter too.

And yes, they keep the chill off you on the sofa. I won't promise you numbers on a heating bill. You notice it the first evening you sit near the window.

But interlining alone won't do it.

Warm air still escapes over the top and round the sides. So the heading wants to sit close to the wall, the curtains should return to the wall at each end, and the hems should meet the floor or the sill. A pelmet or a box over the track helps more than people expect.

The downside? Weight. Interlined curtains need a proper track or pole, fixed into something solid. And they cost more, because there is more cloth and a lot more hand sewing.

In the old Somerset houses I interline nearly every time. In a newer house with good glazing, a thermal lining is sometimes enough.

Not sure which yours needs? Send me a photo of the window and I'll tell you what I'd do.

Karen