Wood-burning fireplace inserts are units that fit inside the firebox of the fireplace to improve its efficiency. Many of these units have glass doors, allowing room occupants a view of the fire. These units reduce the heat lost up the flue of the fireplace to approximately 50 percent.
Wood-burning inserts and stoves add to the pollution levels in the area where they operate. Wood smoke also contains creosote that collects in the flue. Creosote is flammable and causes flue fires.
In the United States, the Environmental Protection Agency certifies new wood-burning fireplace inserts. Certified inserts burn fuel more efficiently and produce less smoke. With proper use, it is possible to keep the area comfortable while consuming less firewood.
The size of the firebox is one of the factors determining the amount of heat the insert produces. Fireboxes range from 1.6 to 3.1 cubic feet and produce from 65,000 to 85,000 British thermal units per hour. A typical full load of wood continues to burn for 6 to 8 hours.
As of 2015, inserts cost up to $2,000. They require a stainless steel connector between the unit and the fireplace flue or a continuous chimney liner, which adds to the installation costs. Many fireplaces require internal rearrangement of the flue to accommodate the insert.