To close a HVAC vent or not?

[jams]

Is is cost effective to close vents? I don't know. Something to think about!

I have a room in my house that I don't use. It has two walls that are exterior walls so the room gets rather cold in the winter.

I have closed the vent in that room for years. I just started rethinking this practice. The room gets very cold so it must transmit the cold to neighboring rooms.

Also, that room as a return vent that returns the unheated air to the furnace to be heated. At times I also block off the return vent.

So is the practice of closing vents saving you money or costing you money?

It is almost like the practice of driving your truck with the tailgate down, which Mythbusters said was less efficient than driving with it up.