We recently moved into a home (built in 1982) and it has a wood
burning fireplace. We love having a wood burning fireplace, but
we've recently noticed the hearth gets very cold and there's quite a
draft coming from the fireplace. We've read and been told to close
the flu and hold a tissue in the fireplace to see if it moves
(indicating a draft through the flu). We've done that and the tissue
does not move. We've used fireplace caulking around the fireplace
between it and the brick surround.

The draft seems to be coming from the vents underneath the fireplace
(sorry, not sure what that's called). It's as if the area around the
fireplace itself is letting a draft in. We want to continue using the
fireplace and hate to block these vents, but we've covered them with
towels for now while it's not being used. Is there a way to remove
this vent covering and insulate underneath there or is there something
we should do at the top of the chimney that will solve this?

Replacing the insert is a bit costly for us right now. Is there
anything else we can do to cut down the draft from under the
fireplace?

Thanks in advance for your help!