A: SH, The amount of money you save with a Chimney Balloon is directly proportionate to how bad your damper leaks. If you have no damper, or you keep your damper open, the Department of Energy says you will consume 30% more fuel to heat your home (conservative estimate). If you do have a damper (and it is in good shape) you are better off, but a metal damper is still not a good way to hold back the cold and keep in the heat.
Imagine you install a metal flap damper on your front door as a mail slot. Aesthetically that wouldn’t be pretty, but it is certain you would feel the cold convecting through the metal, and if you have the slightest warpage to the metal you are going to feel a full on draft. The reason we don’t think about our dampers (and the cold air it lets in) is that it is out of sight up our chimney not on the front door.
One good way to tell if you need a Chimney Balloon is if you stick your hand in the hearth of your fireplace and you notice a temperature change. If it is colder in there, a Chimney Balloon will without a doubt save you money. If you notice no change a Chimney Balloon will help, but it won’t help as drastically because your damper is in better shape than most.
If you want more definitive numbers data. Here is a link to a third party Chimney Balloon field test review that was done with a blower door on a ranch home comparing the Chimney Balloon to a damper, glass doors, and open damper condition. – Jason