A wood fireplace insert, gas fireplace insert, or coal-burning insert is a heating appliance that fits into the opening or protrudes on to the hearth of a conventional fireplace. Inserts are usually made from plate steel or cast iron and have glass doors through which the flames can be seen. The type of fireplace insert which protrudes on to the hearth is more efficient because the sides, top, and bottom provide additional radiant heat.
Inserts often have blowers, which can significantly improve efficiency. Blowers are usually mounted in the front or along the sides of the insert. Some blowers are controlled manually, while others are regulated by a thermostat.
In the past, most installers placed inserts in the fireplace without any chimney connections. This could allow the build up of creosote inside the fireplace, posing a potential fire hazard. To prevent this, the National Fire Protection Association (NFPA) in the US now requires that inserts be installed with a positive connection to the chimney. Inserts must have a connector between the appliance outlet and the first section of the flue liner. This sends the smoke and gases up and out of the chimney more directly, minimizing combustible deposits that condense in the fireplace.
Inserts for fireplaces are heavy, often weighing over 400 pounds. Since inserts need to be removed when the chimney is being cleaned and maintained, they can be awkward to handle. It is a job best left to a professional chimney sweep. In some cases, however, the insert doesn't have to be removed in order to clean the chimney. The insert can stay in place during cleaning if a full relining collar is installed. This is a stainless steel pipe that connects to the insert and goes to the top of the chimney.
A good quality fireplace insert usually costs between $1,200 and $1,800. The price may be higher if accessories need to be purchased, such as a blower, glass door, or catalytic combustor.
Traditional open masonry fireplaces are not effective or efficient heating devices. Traditional fireplaces draw in as much as 300 cubic feet per minute of heated room air for combustion, then send it straight up the chimney. Fireplaces also produce a lot of air pollution. Although some fireplace designs try to get around these problems with dedicated air supplies, glass doors, and heat recovery systems, fireplaces are still energy losers.
Only high-efficiency fireplace inserts have proven effective in increasing the heating efficiency of older fireplaces. Essentially, the insert functions like a wood stove, fitting into the masonry fireplace or on its hearth, and uses the existing chimney. As mentioned above, a flue collar has to be installed that continues from the insert to the top of the chimney. A well-fitted fireplace insert can function nearly as efficiently as a wood stove.
Studies have shown that proper installation of fireplace inserts is crucial. Professional advice should be sought to determine if the fireplace and chimney are suitable for an insert. An inserts needs to be as airtight as possible. The more airtight it is, the easier it is to control the fire and the heat output. The installer should use only approved fireplace insulating materials to fill any gaps between the fireplace mouth and insert shield.
Moving an insert to clean the chimney or liner can be difficult, and is a job best left to a professional chimney sweep. In some situations, a clean-out door can be installed above the insert connection so the insert does not have to be moved as often. Some models have wheels to simplify installation, cleaning, repairs, and other adjustments.