One of the best options for replacement is the Flame Monaco XTD EPA Zero Clearance Wood Burning Fireplace
. This units functions like a wood burning stove, encased in a fireplace chassis. The current unit can be removed and the existing chimney system can be left in position and lined with a flexible 6 inch stainless steel liner. This model functions as an excellent source of supplemental heat, while cutting down drastically on the amount of air pulled from the room during combustion.