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Unlike free-standing woodstoves, fireplace inserts don't benefit from high-density materials like cast iron and stone. To minimize heat loss to the masonry, fireplace inserts utilize a box-within-a-box design with airflow between the boxes to deliver heated air into the room, which is best accomplished with plate steel. Nonetheless, more weight indicates heavier gage steel, which offers greater endurance over time.
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1200 - 2000
2000 - 3000
1500 - 2300
1000 - 2000
1000 - 2000
700 - 1500
600 - 1400
Note: Fireplace insert weight doesn't tell the whole story: the heaviest woodstove construction materials, cast iron and stone, typically aren't used in fireplace inserts.
The most basic description of a radiant wood stove would go something like this: build a wood fire inside a box made of cast iron, stone or plate steel, and the box will radiate heat from the fire into the room, to be absorbed by surrounding objects. The air in the room will gradually heat up from contact with the stove and heated objects, until a level of comfort is achieved.
Stand this box inside a masonry fireplace, and the masonry will absorb most of the radiant energy, transfering some of it into the room, but losing much valuable heat via thermal conduction through the portions of the masonry structure that are exposed to the cold outdoors. To read more about this phenomenon in our Sweep's Library, click here.
The fireplace insert was invented to minimize heat loss to the masonry in fireplace installations. To build a basic fireplace insert, take a radiant stove and attach an outer shell around it with an airspace in between, leaving openings into the room at the top and bottom. The outer shell will reflect radiant energy back at the stove's firebox, superheating the air between the boxes. The heated air will rise and flow out the top opening into the room, drawing cool air in at the bottom to be heated in turn. This process turns the radiant heat that would have been lost to the masonry into convected heat, which is transferred to the room in the form of heated air.
Due to its high heat transfer efficiency when used for the firebox and its heat reflective properties when used for the outer shell of the convection chamber, plate steel is the material of choice for most fireplace inserts. The Hearthstone Clydesdale uses a combination of soapstone, cast iron and plate steel to create a unique combination of gentle radiant temperatures and maximum air convection.