GC: n

CT: According to the National Association of Home Builders, fireplaces rank among the top three features desired by new homebuyers. Unfortunately, fireplaces are also major air gaps—they can send up to 8 percent of valuable furnace-heated air flying out the chimney, making them really fun to look at but inefficient as heating sources. Here’s the good news: You can transform your firebox into an efficient room heater by adding an insert.
An insert, installed by a factory-trained professional (to ensure proper venting and best efficiency results), will draft-proof an open fireplace while the unit’s shell keeps heat in the room and away from the masonry.

S: http://www.thisoldhouse.com/toh/photos/0,,20341633,00.html (last access: 4 October 2015)

N: 1. From the verb insert “to set in, put or place in,” 1520s, from insert, past participle of Middle English inseren “to set in place, to graft, to introduce (into the mind)” (late 14c.), from Latin inserere “to put in, implant,” from in- “in” + serere “join together”. Related: Inserted; inserting. The noun meaning “something inserted” is from 1893.
2. Hearth-mounted insert are models design to be installed on the hearth expansion of a masonry fireplace.

S: 1. OED – http://www.etymonline.com/index.php?term=insert (last access: 4 October 2015). 2. TERMIUM PLUS (last access: 4 Ocrtober 2015).

SYN: hearth-mounted insert

S: TERMIUM PLUS (last access: 4 Ocrtober 2015)

CR: biomass, wood pellet