Seal Fireplace Damper

[Buck Turgidson]

I want to seal the damper of my fireplace, which I never use. I thought it was a narrow opening that I could easily stuff some insulation. However, the damper is about 2' wide, and above it is a large chamber. Only further up the chimney does it taper down to the square terracotta tube. The tube is no more than 12"x12".

Since I can't really insulation from right above the damper, would I gain much by stuffing insulation at the top of the chimney? The chimney is capped of with a metal cap, which should keep the insulation dry, except in a blowing rain.

[JoeSpareBedroom]

I'm thinking of a similar idea, but doing it below the damper. I've got about a foot of just brick. My idea is to cut a piece of cardboard to wedge in there, leaving enough space for a lot of loose pink insulation. I'm going to enclose the insulation in a plastic bag to make it easier to handle if I want to remove it at some point. (Eliminate contact with it, in other words).

[Goedjn]

It's easier to just cut solid foam insulation to fit just below the damper, and prop it in place with a stick, or a television set.

[German Jerry]

I bought an chimney balloon that fixed a similar issue in a zero clearance fireplace that had a leaky damper. If you know the rough size of the area above your damper or if you can measure it with a folding carpenters ruler or tape measure you get a balloon that is apropriate for the size of your chimney. Insert the balloon through the damper opening and inflate it through the valve tube. You can find them at

or I see northlineexpress.com and amazon carries them as well.

I recommend the clear balloon version over the black balloon version since you can buy a clear one of an apropriate size for your damper and it installs into the chimney so you dont have to see it.