Pelmets - an old idea returns?

Story so far we hope to move into a newly refurbished property on a long term let .
Since we Will be living there for some time I am thinking of all the ways I can increse the insolation. I remembered the house of my grandmother had nô double glazing but did have thick curtains ( drapes ) on all the windows And doors most also had pelmets.
For those who dont know what they are its a wooden box that encloses the rail And cuts down on drafts from the window when the curtain is closed.
Have other people tried them?

David

I never knew the proper name for them, but YES they work.

They work even better if you fasten the sides of the curtains to the wall, too. Velcro, pins, snaps, magnets--whatever works for you.