What are fireplace inserts?

By: Richard Winter  | 
Fireplace close-up.

Key Takeaways

  • Fireplace inserts are designed to boost the efficiency of traditional fireplaces, converting them into a closed system that limits heat loss.
  • They come in various types, including electric, gas, wood and pellet, each with unique installation and maintenance requirements.
  • Inserts not only reduce heat loss but can also significantly cut fuel usage and heating costs compared to open fireplaces.

­Ah, the crackle of a fire in the hearth. There's nothing like a blazing fireplace to create a sense of warmth and comfort. However, there's a major downside to the traditional wood-burning fireplace, whether it's a factory-built fireplace or a masonry fireplace: heat loss.

Fireplaces are, by nature, not very efficient. They pull warm air out of the room and into the fire. A lot of t­hat energy -- heat -- is lost up the chimney and through the material that surrounds it. When temperatures drop below freezing, a fireplace exhausts more energy than it creates. The Hearth, Patio and Barbecue Association rates older fireplaces' efficiency at 5 percent to 10 percent [source: Kaufman].


Most fireplace inserts are designed to increase a fireplace's efficiency. An insert is basically a fireproof box that's surrounded by steel or cast iron and fronted by insulated glass, creating a closed combustion system. The steel or cast iron helps to trap the heat. Some inserts have a blower that pushes the hot air back into the room through front vents. Properly installed, fireplace inserts can be a much more efficient supplemental zone heater than a traditional fireplace [source: Wood Heat Organization].

Inserts can be powered by electricity, gas, propane, wood, pellets or coal.

­Electric, gas and propane inserts also offer owners a big timesaving advantage. Consider this: To build a fire, you have to gather the materials, which in some cases involve a tree, an axe and a great workout. Even if you buy wood, you­ still have to haul and store it. There's also preparation involved in setting up a fire: You need seasoned wood, papers and kindling to get it going. Smoke might get in your eyes (especially if you forget to open the flue!) as you tend to the fire to keep it going. And afterwards, you've got to clean all the ash out of the fireplace.

With an electric or gas insert, all you have to do to start the flames is push a button, which, depending upon the model you buy, might even be on a remote.

Read on to learn about electric fireplace inserts.


Electric Fireplace Inserts

­Electric fireplace inserts are the simplest, least complicated types of inserts on the market. Because there is no combustion involved, no venting is require­d. Permits are not needed, either. Just plug it in and watch the simulated flames flicker.

Electric fireplaces include a small heater, which puts out up to 5,000 BTUs (British Thermal Units, a way of measuring heat). Reflective, flickering lights create the illusion of flame. Many electric fireplace insert models allow you to adjust the flame size; they can also be used with or without the heat component, which is beneficial if you live in a hot climate.


Electric fireplace insert users buy them for aesthetic reasons. They may be living in an apartment with a nonworking fireplace. Or they may have no access to natural gas in the area, or they don't want to burn wood [source: Kaufman].

Installation is much simpler for electric inserts than it is for gas and wood inserts. The electric fireplace insert needs only to fit into the fireplace opening. Clearances from mantles, the back of the fireplace and chimney flues don't need to be taken into account. Some say that putting in an electric fireplace insert is as easy as putting a glass on the kitchen shelf (albeit a very, very heavy glass).

The insert gets all its power from one plug, which drops down from the hearth and plugs into a nearby electrical outlet. The price of operating an electric heater depends on your electric costs.


Gas Fireplace Inserts

Homeowners who have access to natural gas can put a gas insert in their fireplace.

These inserts must be professionally installed. A gas line needs to be run to the fireplace. If you already use gas in the house, this could take a few hours, depending on how far away your gas source is. Two small, flexible tubes run down through the chimney; one brings fresh air into the insert for combustion, and the other is for exhaust [source: Kaufman].


Gas fireplace inserts are extremely efficient, typically kicking out between 25,000 to 40,000 BTUs, which is enough to comfortably heat a medium-size room. Their energy efficiency ratings run from 76 percent to 83 percent. Prices range from $1,400 to $3,000 for a top-of-the-line gas insert. Because they're great for zone heating, they can help homeowners keep their gas bills down.

Once the gas insert is installed, it won't need much maintenance aside from cleaning the glass door. There's no need to refuel, and the chimney doesn't need cleaning because gas burns so cleanly. However, because gas burns so cleanly, it can be difficult to determine if there's a leak. That's why a carbon monoxide detector is so important -- it can let you know there's a problem before it's too late. These run about $20 at any home improvement store [source: Kaufman].

"Logs" for gas inserts are made of ceramic or ceramic fiber; they're placed over a burner to give the look of a traditional flame. Vented log usually come with most units. Vent-free log sets are offered on inserts that use an oxygen depletion sensor, which further boosts efficiency. This technology isn't approved for use in all states and can't be used in bedrooms because it requires a closed damper.

Although gas fireplace inserts don't need electrical power, models with a fan or a blower will need to be plugged in to work. Some models come with remote controls and can even run on wall thermostats.

Like your flames the old-fashioned way? Read on to hear about wood fireplace inserts.


Wood Fireplace Inserts

­The main benefit of a wood fireplace insert is that it gives you the beauty of an open fireplace with the performance of a state-of-the-art wood stove. The efficiency rating for wood fireplace inserts generally runs around 50 percent [source: Kaufman] -- less than gas inserts but better than traditional fireplaces.­

A disadvantage of burning wood is the emissions. Wood smoke is wasted fuel that sticks to your chimney as creosote (which is combustible) or is released as air pollution. Some areas have "burn free" days during which homeowners aren't allowed to use their standard fireplace because of air pollution levels [source: EPA].


The Environmental Protection Agency (EPA) certifies all wood fireplace inserts to ensure that they burn wood efficiently, safely and with less smoke. Sized and installed properly, an EPA-certified wood fireplace insert will also reduce wood consumption and reduce maintenance of the insert and the chimney.

The fireboxes of a wood insert run from 1.6 cubic feet (.04 cubic meters) (running hot, this size will kick out about 65,000 BTUs an hour) to 3.1 cubic feet (.09 cubic meters) (85,000 BTUs per hour). Loaded up with wood, they can burn as long as six to eight hours.

The National Fire Protection Association requires a stainless-steel connector between the insert and the chimney's flue liner, or a connector that runs all the way up the chimney (this setup is easier to clean). In many cases, some internal realignment of the chimney is necessary. Wood insert models can cost up to $2,000; installation and the chimney lining will add several hundred dollars more to the cost [source: Lemoff].

Here are some safety and maintenance tips to get the best out of a wood fireplace insert:

  • If you smell smoke, your insert is not working right and could be dangerous.
  • Have your insert, chimney and vents professionally cleaned and inspected annually.
  • If using manufactured logs, use ones made from 100 percent compressed sawdust.
  • Remove ashes regularly, placing them in a covered metal container. Store this on a cement or brick slab, away from wood.
  • Burn only dry wood that's been seasoned, sitting dry for at least six months.
  • Install a smoke alarm and carbon monoxide detector in the general vicinity of the fireplace.

For more information, visit some of the links on the following page.


Frequently Asked Questions

How do you size a fireplace insert for an existing fireplace?
Ensure the fireplace insert fits the dimensions of the existing opening, considering depth, height and width for proper installation.
Can you convert any existing fireplace to use a fireplace insert?
It's possible to convert most existing fireplaces to use inserts, but a professional inspection is recommended to assess the compatibility and safety requirements.

Lots More Information

  • Environmental Protection Agency. "Wood Burning Efficiency and Safety." (Accessed 12/11/08)http://www.epa.gov/Woodstoves/fireplaces.html
  • Hearth, Patio & Barbeque Association. "Fireplace Inserts." (Accessed 12/04/08)http://www.woodheat.org/technology/inserts.htm
  • Kaufman, Don. Head of Sales Training for Lennox Hearth Products. Personal interview, 12/11/08.
  • Lemoff, Ted. Staff Liaison, National Fire Protection Association. "NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances." Personal interview, 12/12/08.
  • The Wood Heat Organization. "Fireplace Inserts: The Cure for Cold Fireplaces." (Accessed 12/11/18)http://www.woodheat.org/technology/inserts.htm