The bigger the room, the higher the ceiling has to be to feel comfortable. I'd still insulate the ceiling of the big room, but I wouldn't necessarily lower it.

The bigger the room, the higher the ceiling has to be to feel comfortable. I'd still insulate the ceiling of the big room, but I wouldn't necessarily lower it. Instead, put in a ceiling fan so that the air doesn't stratify. Fireplace isn't critical unless you're actually using it for heating.