I own a home from ~1940. One end has a chimney and a non-functional fireplace with the damper closed and a ceramic tile secured to the top of the chimney with caulking. Dead 'potato bugs' fall out of the small gaps around the outlets on either side of the chimney breast - note that I removed the outlet covers to paint and didn't replace them yet... My house has a brick facade over frame from the 1940s with some gaps in the mortar. The damper is closed and there is no overt moisture when I open it. I plan to re-open the chimney and place a traditional cap to allow for ventilation. Any experience on whether that will fix my problem? Is it worth it to fill the mortar joints, or is that not likely a part of my problem? Thank You and God Bless.