One of my yellowed heating textbooks has a wonderful drawing of a Victorian radiator that has what looks like a teapot cozy over it. The cozy is made of heavy drapery material and it has a drawstring on its side, giving the folks living in the house a way to control the amount of heat by raising and lowering the curtain. The long-dead writer explains that this is a simple and elegant way to control radiators that are oversized for the space they’re serving, which I thought was delicious. Even then, heating contractors could be, well, let’s just say conservative.
The radiator cozy was a simple way of killing convection and radiation. Considering that many of those old radiators ran on one-pipe steam, and since a one-pipe steam supply valve offers but two choices (open or closed), the cozy delivered relief from having to bend over and twist again and again.