Fireplace Inserts

Prefabricated fireplaces accomplish much the same goal as a masonry fireplace, but at a fraction of the cost. These types of fireplaces usually consist of a sheet metal chassis that is designed for installation into a framed wall opening. They are then vented using a manufactured pipe system, which is enclosed within the structure walls or within a decorative chimney that can mimic the look of a masonry chimney. During the installation of a prefabricated fireplace, there comes a step where the fireplace is physically "inserted" into the framed opening by the installer. It is this installation step that so readily lends this type of fireplace to being labeled as a fireplace insert.

While there are some cross over models of fireplace insert on the market that are dual purpose, allowing installation like a fireplace and as a fireplace insert, these models are in the extreme minority. Almost all fireplace inserts are designed with the sole function of improving the efficiency of an existing open fireplace. For wood burning models, this means converting the existing low efficiency open fireplace into a credible heat source. Wood burning fireplace inserts function like a wood burning stove and feature a closed combustion firebox that allows them to generate large amounts of radiant heat, while using far less oxygen than an open fireplace. Gas burning fireplace inserts share much the same task, being designed to convert an inefficient wood burning fireplace or low efficiency gas log set to a high efficiency heat source.

Much the same as an installer "inserts" a new prefabricated fireplace into a framed opening, there is also the action of "inserting" a gas log set into an existing fireplace to enhance its appearance. Virtually any retrofit of a hearth appliance has been incorrectly classified as an insert at some point, however with the information covered so far, it is simple to see what the classification truly applies to.

For a more in depth look at the design characteristics and operation of fireplace inserts, we encourage you to visit our fireplace insert buying guide.

Open Fireplace vs Fireplace Insert - Efficiency

Lack of operating efficiency is one of the primary reservations that most customers have with using an open faced fireplace. Open wood burning fireplaces have been in use for thousands of years and are a proven concept that has become easy to replicate and employ. The idea of harnessing flame into a relatively small enclosure which would then allow heating of the surrounding stone or brick was a ground breaking achievement that has not changed for centuries. Designs such as Rumford fireplaces, with their shallow walls and tall opening, improved upon the basic design and increased radiant heating of the room. The same concepts that allowed wood burning fireplaces to function as they do was soon employed with gas burning fireplaces. As time went on however, mankind evolved from the survivalist instinct of just trying to stay warm, to fully enclosed structures that we desired to keep evenly heated through all manner of extreme cold.

Unfortunately, the point came were it became clear that heating demands outstripped the abilities of open fireplaces Installation of doors and the use of dedicated combustion air ducts offered some improvement, but the fundamental design of open fireplaces ensured that they would always remove large quantities of air from the building as they operated. The strong upward draft of flue gases essentially causes an open fireplace to work like a vacuum pump. While they do offer radiant heat, the continuous draft pulls so much ambient air from the home that the fireplace can actually be counterproductive. The immediate room is warmed, but all rooms further away begin to cool as make up air is pulled through every gap in the outer wall of the home. For tightly built homes, opening a door can result in a huge inflow of cold outside air as the home struggles to find a pressure balance again.

Fireplace inserts as a whole are designed to solve the problems experienced with traditional open fireplaces. For wood burning models, the fireplace is converted into what is essentially a built in wood stove. The amount of oxygen consumed by a wood burning insert is typically only 5 to 10 percent of what is used by an open fireplace, meaning that pressure issues in the home are alleviated and the consumption of wood is greatly reduced. Modern fireplace inserts utilize a highly aerodynamic firebox that recirculates wood particles for a very complete burn, meaning that the efficiency of the fireplace housing the insert is boosted from a flat or even negative efficiency level to up to 85 percent efficiency.

Gas burning inserts also yield impressive efficiency gains. Direct vent gas models feature a dual intake and exhaust system, which allows the appliance to pull outside air for combustion while exhausting what little waste heat there is to atmosphere. The integral burner systems are engineered for optimal heat output and most inserts feature a circulating fan to push the heated air into the room. Vent free gas inserts omit use of the chimney entirely, meaning that they are nearly perfectly efficient and can create a credible supplemental heat source where there was previously a poor performing open fireplace.

Open Fireplace vs Fireplace Inserts - Design

More obvious than efficiency differences is the visual variance between fireplaces and fireplace inserts. Because they are known and often accepted to be a low efficiency heat source, most models of fireplace take extra steps to be visually appealing. After all, if the fireplace is both inefficient and ugly, what is the point of having it? Fireplaces will focus on having a wide and often tall viewing area. For masonry fireplaces, the interior is usually constructed with firebrick or refractory walls that are visually pleasing. The surrounding fireplace opening is usually clad in decorative material, such as brick, stone, marble, or granite. Because they do not radiate much heat to the adjacent sides of the fireplace, a broader range of mantels and surrounds can be used. In short, the emphasis on visual appeal is maximized with an open fireplace to make the fire viewing experience as cozy as possible.

While fireplace inserts are certainly developed to be visually pleasing as well, their retrofit nature means that there are some design compromises that have to be made. These compromises are usually the biggest sources of hesitation for customers on the fence between leaving their fireplace open for better viewing or installing an insert to increase efficiency.

The biggest item of note is the requirement for a surround to be used. A fireplace insert will be designed to fit into the existing fireplace opening and while it is certainly ideal to minimize the difference in size between the two, there will always be a gap that must be covered. Fireplace insert surrounds or shrouds are usually manufactured from stamped steel or cast iron and will serve as the cover needed to conceal the gap. While newer models offer surrounds that are more visually pleasing than past offerings, there is still a noticeable detraction to the overall looks of the fireplace.

Going hand in hand with the use of a surround is the need for a fireplace insert to be physically smaller than the fireplace itself. No matter what model of insert is used, the viewing area is guaranteed to be smaller. The need for the fireplace insert to contain all the necessary gas valve components, liners, and fire brick means that some space will be eaten up by these items, leading to a smaller opening for fire viewing. For the occasional fireplace user that is not terribly concerned with efficiency, these trade offs may not justify the installation of the insert.

Because of their more efficient design, fireplace inserts also may necessitate changes in design to the fireplace surround or mantel. Materials that previously met clearance requirements for an open fireplace may now become dangerously hot and require relocation. Depending on how elaborate the fireplace mantel is or the sentimental value it may hold, this is an issue that could be difficult to address.

For additional information on working a fireplace insert into your room decor, we recommend taking a peek at our room design guide.

Open Fireplaces vs Fireplace Inserts - Venting

In almost all cases there is an existing fireplace that a consumer is considering retrofitting a fireplace insert into. It is rare to hear of an insert being installed directly into a newly built masonry or prefabricated fireplace, although there are rare cases. As such, we will not cover the differences in overall venting costs between these two categories of appliances, but will instead focus on the different design aspects and what can be expected when installing fireplace insert venting.

Open masonry fireplaces will utilize clay flue tiles for venting purposes. Often referred to as terra-cotta flues, these tiles are made of a very durable material that is sized to the opening of the fireplace. Prefabricated fireplaces will also have purpose built flue systems, but instead will rely on prefabricated chimney sections constructed of stainless steel, galvanized steel, or both. The design characteristic that both setups have in common is that they are much larger than the venting system needed for a fireplace insert. In wood burning applications, the higher level of emissions means that the chimney will need to be cleaned more frequently. Gas burning systems are very clean burning and will not necessarily require any additional maintenance over a gas fireplace insert.

Gas, wood, and pellet burning fireplace inserts are all designed to be vented through a flexible liner system that is routed within the existing fireplace flue. For wood burning systems, the liner is commonly six inches in diameter and is manufactured of stainless steel. Gas burning systems will utilize an aluminum liner system and will usually feature a pair of 3 inch liners. One liner supplies combustion air for the fireplace insert, while the other will vent exhaust gases. Pellet inserts will use a stainless steel liner similar to wood burning models, but the diameter is usually only 3 to 4 inches.

When installing an insert, it is important to consider just how much space will be available to attach the chimney liner to the top of the appliance. If there is very little space between the top of the insert and the top of the fireplace, it could be difficult to make the appropriate connections. Masonry fireplaces have a large smoke chamber that allows the flexible liner some space to contour into the flue, however prefabricated systems usually have a flat ceiling with no extra space to route the liner. As such, it is important to ensure that the fireplace insert being selected has a flue collar that aligns with the chimney flue of the fireplace.

Additional coverage on fireplace and fireplace insert maintenance can be found in our fireplace maintenance guide.

Open Fireplaces vs Fireplace Inserts - Maintenance

When it comes to frequency of maintenance, gas burning fireplaces and fireplace inserts have almost no differences. Common components such as gas valves, thermocouples, and log sets follow the same maintenance schedule and vent systems require only periodic inspection for both appliance types.

The most difference can be seen between wood burning fireplaces and wood burning fireplace inserts. As previously mentioned, wood burning fireplaces produce large quantities of particulate pollution, leading to a build up of ash and creosote on the chimney walls. Even a well constructed, hot burning fire will produce this byproduct material. For a regular user, it is not uncommon to have to clean the chimney twice or more during the burn season. Installation of a fireplace insert improves efficiency vastly. Because of their integral reburn systems, fireplace inserts produce far less particulate pollution, meaning that the flue liner will remain cleaner for longer periods. When operated properly, it is rare that the liner will need to be swept more than once a season. Some occasional users have found that a cleaning is required only every other season. For a customer that has access to a plentiful supply of fuel logs and is considering using a fireplace insert as a primary heat source, the reduced level of maintenance can be a real life saver.

Fuel and Electrical Considerations

When it comes to gas fireplace inserts, the requirement for a gas line to be run into the existing fireplace is something that must be kept in mind. Many consumers will at some point decide that burning wood is not worth the effort and so choose to convert to a gas burning model. Most cities and well established towns will have infrastructure in place to supply natural gas to homes, but it is not a guarantee that the house will have a gas meter in place, especially if the house was built with only electric appliances installed. The cost of having a meter and supply line should be considered before making the purchase of the insert.

In rural areas, natural gas may not be available, with the house being supplied by a propane fuel tank instead. As with natural gas, if the home does not already have the tank in place, the infrastructure must be put into place before the installation can proceed. In both natural gas and propane installations, the cost of having the gas infrastructure installed can be substantial. The cost of the insert itself coupled with the cost of the gas piping may lead the customer to consider a wood burning insert instead. While the need for fuel logs will continue, the efficiency of the fireplace insert is sure to make a difference in how much wood is consumed.

To increase their overall efficiency, most inserts utilize an electric blower system that pulls the heat from the fireplace insert chassis and forces it into the room. While this makes a huge difference in thermal efficiency, it also necessitates the installation of a 120 volt power source to supply the fan. The cost to add an outlet or wire an electrical pigtail to a nearby outlet should be considered when installing a fireplace insert. In some cases, an electrical plug may be close enough that a flat piece of panduit can be installed along the edge of the fireplace and used to conceal a light gauge extension cord.

Final Considerations

In addition to clarifying the differences between a fireplace and a fireplace insert, you should now have a clear understanding of what appliance will work best for your installation. There is no true "one size fits all" model of fireplace or fireplace insert and it is best to work with a skilled NFI certified technician, such as the professionals at eFireplacestore, to determine your exact needs. With a clear understanding of your vision for the room, the right appliance for your application can be installed, leaving you with the sense of satisfaction that comes from making the right decision.