As I understand it, unless you have a fireplace insert or at least a glass front etc, a fireplace will SUCK WARM AIR OUT of your house, more than warm it up—particularly after the fire dies down. You might want to fix the one in the kitchen to prevent that, too.
We do have the glass doors. We used these fireplaces for 20 years when the kids were small. Kept us totally smothered - had to run around in shorts in the winter time.
We did have built in fans, but didn’t really use them all the time, as the larger fireplace had a pretty big firebox and hubby kept the fire going full blast.