I have a fireplace I am not using, the damper is closed unless I'm letting out a bird. In 35 years I have never had a fire in it.
Birds yes, fire no. Bird fit thru the top--so much for a spark arrester.
I ran the HVAC-calc program and 20% of my heating bill is used to send hot air up the flue.
Is there an easy way to seal this off so that it can easily be unsealed later, like when I hear a bird in it? It is wood and stucco with a tin can inside. I have thought of putting a balloon up there.