Q: Jason – I am relatively certain of the dimensions of my flue and the area in which I wish to install a Chimney Balloon. I think it is a 32″x14″ opening. Would a 36″x15″ Chimney Balloon work for this size flue? – RT
A: RT – When you say you are “relatively sure” of the flue dimension it makes me think you may not have actually measured this area of the flue with a ruler or tape measure. It you have not, I would encourage you to measure it again. You will find that a wooden folding carpenters ruler is very useful to measure up in a flue. Bend the ruler into an L shape and use it as a feeler gauge to reach up and get a measurement of the area you plan to install a Chimney Balloon into. OK, now that you have measured and found your flue to be 32″x14″ as you previously said, then yes a 36″x15″ Chimney Balloon will work just fine. Even though your Chimney Balloon will be a little large, it will function perfectly.
As a side note, you can easily install a Chimney Balloon that is no more than 6″ too large in either dimension if your chimney flue area is at least 24″x12″. However, do not buy a Chimney Balloon that is too small for a flue dimension. That is like having a submarine door that is a little too small…it just doesn’t work.