I'm not sure what your situation is. You said 4 sided in 3 rooms. Will you be able to see into the other rooms through the fireplace? Where does the fourth side face? Is this a common chimney with four fireboxes?

Regards

You will likely need a power exhaust on the chimney top. Flues are sized relative to the openning. You have too mcuh openning size for any practical size of flue. You also need to consider where the makeup air will come from

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