It's Curtains for Wasted Room Heat

Central heating radiators are usually sited under the window in order to avoid flows of cold air from the window into the room (Fig 1).  Unfortunately this results in a lot of rising warm air from the radiator getting behind the curtain and going out the window, double glazed or not.

I have overcome this problem by fixing a shelf to extend the window sill out into the room, allowing me to place the drawn curtain on the shelf, which effectively separates the warm room from the cold glass (Fig 2).

We've had them up for four months now, and they work fine.  There are no drawbacks (see what I did there?). Nearly all the heat from the radiator comes into the room.

Here is what it looks like:

Before

Shelf in place

Curtain shelf in action, saving heat.

I hope this may inspire others to cut their fuel bills a bit