Moreover, the way fireplaces work is that the fire heats up some kind of heavy construction (cast iron, brick, etc) and that then radiates heat. Not every fireplace is built that way - some of them are decorative and will actually make you colder.

Quite a few people found out in not a nice way last time Texas has winter storm.

Yeah if you want to rely on it as heat source you should probably get something modern that doesn't waste exhaust heat and doesn't suck the air out of the room getting more cold air in. Not just "a hole in a roof above a fire".

I am the original poster. As I said in my post, the fireplace is mainly decorative and we are NOT relying on it for heat. However it is our plan B/C if shit hits the fan, in which case huddling the family in front of the radiant fire is a much preferable alternative to dying of cold, efficiency aside.