Where to Measure a Heatelator Pre-Fab Fireplace

Jason, I have a fireplace in our basement that I want to plug since we do not use it.

There is a metal damper that operated on a hand crank just 3″ above the fireplace opening. However, about 14″ above the damper is an 11″x11″ terra cotta flue tile that I think I can easily get a Chimney Balloon into. The website instructions say to buy a Chimney Balloon that is a little large…should I get a 15×15 or 12×12 Chimney Balloon and should I buy a HEK extender with it? – RW

Dear RW, You sized up this application well and your instinct is right-on to go with a 12×12 with a HEK Extender.

11″x11″ is a very common size flue tile, and experience tells me that a 12×12 Chimney Balloon is the perfect size to plug that flue. Since your flue tile terminates just 14″ above the damper then you can certainly use a HEK extender to get it up there and installed. I have attached some pictures that are similar to your install. – Jason