Conventional masonry fireplaces can lose between 80 and 100 percent of their heat plus an additional 10 percent of the heat already in the room. They can actually remove more heat than they supply. One of the most redeeming features of these fireplaces is that they require low clearance between themselves and other combustible surfaces. They can be placed on any floor of the home without architectural reinforcement and can be quickly installed. You must flow manufacturer's instructions very carefully if you plan to install one yourself.
Manufacturers achieve high efficiencies in various ways.
Often fireplaces have tight-fitting glass doors and some type of air control system. Means for achieving high efficiencies differ between models. Because of their many benefits, factory-built fireplaces are becoming a popular option for many homeowners and builders. They can be used simply for enjoyment and aesthetics or, with some of the more expensive models, they can be used as a source of heat. They have many different designs and can be faced with many types of materials, such as marble, granite, block, tile, and stone.