Thanks for the response.
So, you wouldn't recommend a chimney top damper, then? What if we got one, but left it open during humid months? I ask because the damper at the bottom is super drafty. I probably exaggerated when I said "no odor at all ever before." On really windy days, we could hear wind in the fireplace and get a bit of odor (nothing like what we have now).
If I got the top damper but only closed it during winter or windy days, what would you think?
What else should I do to help keep the chimney dry? I inspected the rain cap, and it seems fine. None of the multiple guys who inspected it said anything. I also had the bricks sprayed with sealant when we bought the house.
I had conflicting opinions regarding the crown. A couple guys said the mortar crown is fine because the only crack in it is repaired. A couple said it needs to have metal over it (I've heard recommendations from galvanized, to stainless steel, to "skirt style"--still no idea what that means). Then I've read on several forums that the best thing to do is to just paint some of the "polymerized" sealant onto the mortar crown...
So, my plan right now is to:
Get an airtight fireplace door. I'd been considering this anyway. The door that's on there now needs to go no matter what (it's hideous), and an airtight door with ceramic glass will increase energy efficiency and prevent smoke into the house even on windy days.
Get a Lyemance damper, but only close it during winter and on windy days.
Install a gas log lighter so I can heat up the fireplace/chimney air to reverse the flow and dry out the chimney if this happens again (without having to build an actual, stinky wood fire).
With these two items, I wasn't really planning on a chimney balloon.
I don't know, what do you think?
As far as the heatilator, there's no sign of moisture in the fireplace. I even crawled into the fireplace and stuck my arm up into the smoke shelf and the flu and everything was bone dry. I buy that there's moist air building up, but I don't think it's so bad that the fireplace itself is wet and rusting the heatilator. Would any of my proposed fixes change this?