Fireplace inserts were first invented in 1896 by Joab R. Donaldson of Oliphant Furnace, a coal mining town in Southwestern Pennsylvania. The original design was intended to improve the heating efficiency of coke and coal burning fires, the common fuel of the times.
The modern fireplace insert has the same primary purpose, to improve the heating efficiency of an existing fireplace. The insert fits into an existing fireplace, most likely a masonry fireplace that was originally intended for burning wood. Traditional wood-burning masonry fireplaces, while appealing in terms of aesthetics and ambience, are not at all efficient converting only 15% of wood’s energy into useful heat. The majority of the heat goes right up and out of the chimney instead of heating the home.
Our Guide to Fireplace Inserts
Our guide to fireplace inserts is designed as the starting point for homeowners in the initial stages of learning about fireplace inserts and solutions for converting their traditional fireplace into a more efficient heat source. Selecting the right model for you and your home can be a difficult decision to reach with so much jargon and choice on offer. Our aim is to simplify the process and help you decided which type of fireplace insert and model is best suited for your unique needs.
If you already know the basics of fireplace inserts, and know what type of insert you need, please skip to one of our product guides that include reviews and buying advice:
Gas Fireplace Inserts | Electric Fireplace Inserts | Wood Burning Inserts |Pellet Stove Inserts.
If you have any questions regarding the information on this page or any of the fireplace inserts we discuss, then feel free to share them in the comments section or the fireplace insert section of our forum and we’ll try to answer you as best as we can.
Quick Picks: Examples of Fireplace Inserts
What is a Fireplace Insert?
A fireplace insert is a firebox (the part of a fireplace where the fuel is burned) surrounded by a steel or cast iron shell that fits into an existing masonry fireplace. The fireplace insert takes the place of your masonry fireplace and connects to the flue and chimney for external exhaust venting. The main purpose of a fireplace insert is to make your existing masonry fireplace more efficient but there are added benefits such as safety and compliance with changing environmental regulations.
Fireplace inserts are specifically designed to fit into your existing masonry fireplace. If you are planning to remodel your home, rehab a new home, or are designing the home of your dreams, you most likely won’t need a fireplace insert. You will instead be interested in purchasing a new fireplace which will give you more control, flexibility, and options. If this is the case, you’ll want to check out our fireplace buying guide.
How Does a Fireplace Insert Work?
Fireplace inserts work by drawing air into the fire chamber, heating that air, then circulating the heated air into your living space instead of being quickly lost up your chimney and into the surrounding masonry.
Air from your living space will also flow into space between your firebox and steel case to be heated, increasing its efficiency further.
Frequently, the heat is also recirculated into your home with a stove blower. This gradual dispersal of heat prevents it from being lost up your chimney and the blower prevents heat being isolated to a single “heat spot” in your living area. Since heat rises, the heat spot will generally be just beneath your ceiling.
The best gas fireplace inserts are exceptionally efficient, commonly producing between 25,000 to 40,000 BTUs, which is ample to comfortably heat a medium-size room. While their energy efficiency ratings range from 70 percent to 80 percent.
There are many types of gas fireplace inserts, but the best ones are usually equipped with a selection of innovative features that provide ease of use and optimum heating performance.
These include remote controlled models where the thermostat can be easily adjusted with the click of a few buttons, additionally, there are specialized models that can be fitted into an electric fireplace and natural gas fireplace inserts that remain popular.
Will Your Existing Fireplace be Compatible with a Fireplace Insert?
The vast majority of fireplaces are of one of a number of standard sizes which should enable you to easily match your existing fireplace with an available fireplace insert. See this excellent article from Best Choice Home Inspections on Fireplace Design and Dimensions.
Before you start shopping for a fireplace insert, you’ll want to carefully measure each dimension of your existing fireplace including the fireplace opening, the depth and width of the firebox, and the rear firebox wall height and width.
HEIGHT – UP AND DOWN
Using a measuring tape, record the height of your firebox from the opening, the rear and the lintel (more on this in the next paragraph). If you have a fireplace with and arched opening, make sure you take down the dimensions at the highest and lowest points. Generally speaking, you want to use the smallest of these measurements for your final report.
WIDTH – LEFT TO RIGHT
You now need to measure the width of your firebox from the fireplace opening (the face or exterior measurement) and the rear (interior). Cross-check the width at different heights to make sure your firebox is symmetrical. If your firebox is square, the width should be the same at all points but some fireplaces have angled sidewalls will have different dimensions based on where you take your measurements. If your firebox has angled sidewalls, be very careful to accurately measure the width of the rear wall.
DEPTH – FRONT TO BACK
The depth is the distance from the face of your firebox (the front of your fireplace) to the back wall. Make sure to measure the dimensions of your fireplace depth from the center of your firebox not along the edges just in case they are tapered or angled.
MATCHING YOUR MEASUREMENTS TO AVAILABLE INSERTS
Most fireplace inserts have one number in the product or model name. That number related to the fireplace opening width. However, those numbers are quite often rounded up so make sure you look at the product dimensions in the listing or product specifications sheet. The specifications sheet or user manual should include full details of all the measurements you need to ascertain whether it will fit snuggly into the dimensions of your fireplace.
Don’t be concerned if you have some gap on the interior. The insert is well insulated and it doesn’t matter if there some space between the insert casing and the fireplace wall, it won’t impact performance at all.
Some fireplace inserts come with fronts and faceplates (or surrounds). It’s unlikely that any fireplace insert will fit perfectly into your fireplace, as if it were built-in during the home construction. That’s where the fronts and surrounds come into play. They’ll cover over any visible gap between the fireplace insert and your fireplace wall. So the most important measurements are those for the interior of your fireplace. If the insert won’t fit into your fireplace, you’ll be faced with the arduous task of repacking the insert and shipping it back to whichever retailer you purchased it from. Not a fun task!
Once you’ve determined the dimensions of your fireplace, you can proceed with searching for your preferred model. Thanks to the popularity of inserts, manufacturers are producing more insert designs to meet the style demands of the modern consumer using a variety of technologies. But before we move into fireplace insert product reviews and recommendations, let’s first explore inserts by types of fuel.
Types of Fireplace Inserts
1. Gas Fireplace Inserts
These are the most common type of fireplace insert due to a combination of heating performance, energy efficiency, compliance with local emissions regulations, and ability to replicate the look and feel of a real fireplace.
Most gas fireplace inserts are designed to run on natural gas, the gas most commonly used for home heating, ovens, and dryers. They can, however, be adapted to run on liquid propane. Newer, modern models running on clean burning ethanol have recently hit the market.
There are many features and options to consider when purchasing a gas fireplace insert. The first option for you to consider is how to vent the exhaust fumes from the gas fireplace. There are three main vent types for gas fireplaces. The first, and most common, is direct venting which draws air from the outside through one vent and exhausts to the outside using a separate vent. Direct vent gas fireplace inserts can vent vertically (i.e. using your existing fireplace) or horizontally (useful if your existing chimney is blocked or in need of expensive repairs). Direct vent fireplaces are always sealed with a glass front.
The second type of gas fireplace vent is called a b-vent. B-vent gas fireplaces draw air from the room, heat it, and recirculate it while the exhaust fumes are vented vertically through your chimney. These fireplace inserts remain open at the front, often protected with a metal curtain screen, which can provide more ambience than a direct-vent model.
The third venting option for your gas fireplace insert is called ventless or vent-free as it requires no outside venting. Ventless gas fireplaces are highly efficient (99.9% in most cases) and produce very small amount of exhaust fumes. They draw air from the home, heat it, and recirculate it. While highly efficient, ventless gas fireplace inserts do produce some exhaust which is vented back into the home.
For more information on gas fireplace insert options, features, and product recommendations, see our detailed buying guide: Best Gas Fireplace Inserts – A Comprehensive Guide.
2. Electric Fireplace Inserts
Electric fireplace inserts are mainly for people who value the ambience factor of a fireplace over its capability to heat a room or home. New, modern, electric fireplace inserts can look very realistic with flames dancing behind the screen and provide a warm, romantic, centerpiece to a living room, bedroom, or even a bathroom.
Electric fireplace inserts have other benefits. They’re typically far easier to install than wood or gas inserts because they require no venting or gas line installation. They also come with lots of cool optional features such as the ability to control it with an app from your phone or hook them up to Alexa or Google Home.
However, the heating capacity of an electric insert is limited. Of all the electric fireplace inserts that we researched, the most powerful one we found only had a heating capacity of 5,000 BTUs, insufficient to heat even a small living room if relied upon as the primary heating source. This is why electric fireplace inserts are typically used for ambience and design-appeal only and are more popular in year-round warm weather climates such as Florida and Texas.
For more information on electric fireplace insert options, features, and product recommendations, see our detailed buying guide: Best Electric Fireplace Inserts of 2020 – A Comprehensive Guide.
3. Wood-Burning Fireplace Inserts
For a lot of people, nothing can compare to the sound, smell, and overall ambience of a wood-burning fireplace. In a lot of places, wood is still the cheapest form of fuel so it makes sense to heat a home with it.
A wood-burning fireplace insert will convert your inefficient traditional fireplace into a far more efficient heating unit. These inserts are typically made from cast iron, have a ceramic glass door front, and a brick-lined interior for superior heat distribution.
Wood-burning fireplace inserts work in a similar way to gas fireplace inserts. They draw in air which is heated by the firebox and then radiated out into the room often with the help of a blower to aid in heat distribution. These inserts can raise the energy efficiency of your traditional fireplace from 15% up to 70%, drastically increasing wood burn times (the amount of time a single load of wood will burn from ignition through to smoldering), and heat output as measured in BTUs.
EPA regulation governing fireplace emissions may have necessitated your search for a fireplace insert. Many of these wood-burning inserts are now EPA compliant with very low emission rates due to their impressive fuel-to-heat conversion efficiency.
Wood-burning fireplace inserts are an excellent option for homeowners with a low-cost source of wood and a place to store it. For more information on wood-burning fireplace insert options, features, and product recommendations, see our detailed buying guide: Best Wood-Burning Fireplace Inserts – A Comprehensive Guide.
4. Wood Pellet Fireplace Inserts
Pellet inserts are another excellent option for converting your inefficient traditional fireplace into an energy-efficient, powerful, clean-burning heat source. Wood pellet inserts can improve the efficiency of your fireplace from 15% to over 80%.
Here’s how a pellet insert works: You pour pellets, made from compressed hardwood, into the storage hopper located at the top of the unit. An electric auger delivers the pellets from the hopper to the burn chamber. Sensors within the stove monitor the fuel supply and tell the auger when to drop new pellets. It will put in just enough pellets to keep the fire burning small but extremely hot. Pellet inserts are also fitted with a convection blower that draws room air into the stove and blows heated air into the room.
Pellet stoves and inserts are often preferred to wood stoves and inserts because of they use a more environmentally-friend source of fuel. Compressed hardwood pellets are made from compressed sawdust and waste wood that would otherwise be dumped. They are also considered carbon-neutral because the amount of carbon dioxide produced during burning is similar to that which is released when wood decomposes naturally.
Wood pellets are available at many hardware stores and typically come in 40-pound bags which should provide enough fuel for 24 hours of burning and cost about $5, significantly cheaper than buying wood.
For more information on wood pellet insert options, features, and product recommendations, see our detailed buying guide: Best Wood Pellet Fireplace Inserts – A Comprehensive Guide.
5. Fireplace Log Sets
Our fifth and final fireplace insert option is the most simple, a fireplace log set. If you’re interested more in the look and feel of a fireplace than actually using it as a heat source, you might want to consider the cheapest option of all, a fireplace log set.
Fireplace log sets are available in both gas and electric varieties. They are designed to fit into your fireplace and replicate the look of an actual fire. However, without a steel or cast iron casing, they won’t work well as a heat source as you’ll have the same problem you have with your traditional wood-burning fireplace – you’ll lose most of the heat up the chimney.
Log sets are a good, low cost, option for people who want the ambience of a fireplace but aren’t concerned about relying on it for a heat source.
What Should You Look For in a Fireplace Insert?
When choosing an insert for your fireplace, you want to look for the best features that are designed to optimize and improve the function of your insert, the most popular innovations offered by modern manufacturers include:
Heat Output – Measured in BTUs per hour (British Thermal Units). To determine the number of BTUs you need to heat a room or home, multiply the square footage by 20. For example, if a room has 1,000 square feet, you would require 20,000 BTUs to heat it..
Thermostat control – The best inserts come with thermostat control, this is incredibly useful as it allows you to easily adjust and control the temperature range and also the ability to set programs and possibly even control the fireplace remotely via a phone app.
Blower – Most insert options come with an option to add a blower or fan. Higher quality units may come with an integrated blower, other options will include a blower as an add-on at an additional cost. Blower power is measure using CFM (cubic feet per minute) and most fireplace blowers range from 60 CFM to 180 CFM.
Glass Fronts – Most inserts come with glass front or glass doors (in the case of wood-burning inserts). The type of glass is important to note for heat transmission. Lower cost models typically come with tempered glass and higher-end models with ceramic glass which provides better heat transmission. Also look out for air wash systems, an innovation that helps keep the front class clean so you can continue to enjoy your fire without the need for frequent manual cleaning.
Ignition Type – Electric ignition provides convenience and removes the need for a pilot light, saving up to $10 a month in fuel. Other ignition options include safety pilots and match light ignition (exactly as it sounds). If you choose a model with electric ignition, make sure that it has a battery powered backup or match light backup just in case you have a power outage.
Top Picks: Gas Fireplace Insert Reviews
#1 Napoleon Vent Free Natural Gas Fireplace
Founded in 1976 by Wolfgang Schroeter, Napoleon fireplaces is a world leader in the heating sector, with a five-star reputation to match.
The GVF36-2N by Napoleon is a large ventless gas fireplace insert that is ideal if you want to increase the efficiency of your natural gas fireplace.
The fire’s design brings both the traditional charm of the natural wood burning logs with dynamic dancing flames as well as a contemporary touch thanks to the outer metal casing and black louver kit, perfect for people who want the benefits of both form and function.
The great thing about Napoleon is that they provide the ability to customize your fireplace in multiple ways, which is great if you are looking to match your fireplace to a specific interior design décor.
This includes additional trims and surrounds that can be purchased for the fireplace, as well as various trivets and louvers, ideal for those looking for the ability to make a basic fireplace look extra special.
Heat Output & Efficiency
With this vent-free gas fireplace insert, you can achieve a heat output as high as 30,000 BTUs, which is ideal for small to medium-sized homes. This model allows you to easily adjust the heat output by controlling the flame by up to 50% for maximum heat adjustment, maximum comfort, and maximum efficiency.
This control will be especially welcome during winter when the temperature starts to drop. The best part is you can adjust it and turn it off from the comfort of your seat thanks to the digital remote control.
The black fireplace louver kit is also included with the GVF36-2N, which increases the air circulation inside your fireplace and adds a crisp visual element.
Overall, gas is a very clean fuel, with very few pollutants and toxic emissions when compared to other fuel sources. However, carbon monoxide gas that is odorless is a real danger to gas fuel users, which is why its good to know that this model by Napoleon comes fitted with an oxygen depletion sensor.
This shuts the pilot off before oxygen drops below a safe level. This safety feature is a wise investment and must-have feature for the modern gas fireplace user.
This model also comes with a handy safety screen that can be easily detached, which is designed to act as a barrier, keeping your family safe from contact with the intense heat of the open flame.
Although this is not heat proof itself, so caution must still be exercised, especially when concerning animals and children. Still, it is certainly a welcome level of extra protection.
Perhaps one of the downsides of this model is the absence of a ceramic glass window, which in our view would increase safety.
However, you can easily make use of the safety screen that’s included and if you have a young family or pets, then a safety gate is always advised in any case. Having said that many people prefer having no window panel as they enjoy viewing the naked dancing flames, so this is largely down to personal preference.
#2 Duluth Forge Dual Fuel Vent Free Fireplace
Duleth Stove and Fireplace was founded back in 1992 by Matt Boo and Jason May, who were both residents of Duleth and had years of experience in the hearth industry prior to deciding to design and manufacturer their own products.
Today Duleth holds a fantastic reputation and 5-star customer reviews are standard for their collection of hearth and fireplace products.
Appearance & Design
The Duluth gas fireplace insert is available as a standard insert that includes a burner, logs, and thermostat remote control. There’s also the option of paying a little more and purchasing it with various wooden surrounds, including the wood colors oak, tobacco, and cherry, ideal for those without an existing stone masonry fireplace.
Since this fireplace is vent free, it can be installed without a chimney, however, please check local codes as some states, such as California do not permit ventless fireplaces.
Heat Output & Efficiency
The fireplace itself is designed to look like a traditional log fire, which it pulls off quite well when in operation. You can add a surround to this fireplace quite easily, however, bear in mind that it does require a fireplace clearance of at least 1/2 inches.
The fireplace also comes packed with an array of tech to increase its efficiency and ease of use, including a remote control, electronic ignition to the pilot and a blower to circulate the warm air evenly throughout your home.
The heat output of the fireplace is an incredible 32,000 BTU’s, which is superb for the price point and ideal for heating small to medium sized spaces of around 1,500 square feet. The instructions also state that this fireplace can be used with liquid propane (LP) in which case the installer needs to leave the blue plug inserted into the rear of the gas valve.
The blue insert depresses the valve’s internal plunger which allows the LP to flow through the valve and without that piece inserted the valve does not open. This is a straightforward process and you are provided with everything you require, which is great for the price.
#3 Sure Heat Burnt River Oak Vented Gas Log Set
Founded by Michael Mulberry – Sure Heat has a long history and a wide-ranging amount of different hearth, barbecue and patio products on offer.
They were one of the pioneers of modern wood log sets and first began experimenting with their development back in the 1980’s. Today, they are a leader in the field and a highly trusted brand in the US and across the globe.
Appearance & Design
The Burnt River Oak insert offers a great solution for homeowners interested in converting an inefficient traditional wood burning fireplace into a more efficient gas fireplace without the need for a costly remodel.
This unit will help to transform the appearance of a traditional fireplace as it realistically creates the look of a mature wood burning fire. These logs are extremely high quality and have attention to detail in mind, which unfortunately can’t be said about many other log sets on the market.
They are made from ceramic, an extremely heat-resistant material and have been hand painted in great detail to give the impression of genuine wood logs. The detail and size of these logs are great for the price point.
Selection Of Sizes
This gas log set is available in two sizes – 18 and 24 inches. The set itself has been designed to fit fireplaces with dimensions of at least 36-inch front width; 15-inch depth; and 25-inch back width, so make sure to measure your fireplace before ordering.
This log set is Canadian Standards Association (CSA) approved and has an efficiency rating of 99%, so is ideal for those looking for an efficient log set insert. The ceramic logs and the metallic stand itself will help reduce heat loss since the heat will be retained for longer and radiated into the living space as opposed to being lost up a chimney.
This set includes the connection hardware, a u-shaped dual burner, pan, grate, and shale. However, be aware that this log set log set does not include the gas valve, so it will need to be purchased separately.
Selection Of Sizes
The 18-inch set is designed with small fireplaces in mind and so fits those with minimum dimensions of 28″ front width; 15″ Depth and 21″ back width. It is a nice looking set, ideal for those looking for a smaller, yet good looking log set.
Other size options include a larger 24-inch set made to fit all fireplaces with minimum dimensions of 32″ front width; 15″ Depth and 24″ back width. Therefore, it goes without saying that you need to measure your fireplace dimensions before making your order!
Heat Output & Efficiency
Although it doesn’t come with casing or a surround, this log set definitely does the job of adding both style and efficiency to any gas fireplace. The fact is that many individuals prefer the look of a gas log set and that is fine, but you should not expect the same efficiency and financial savings you would gain from a fireplace insert.
Oh and don’t forget that this set requires an open and working flue! If you are looking for a vent free gas log set, then check out the other Sure Heat set above.
Ultimately, the gas fireplace insert you choose to keep you and your home warm is both a personal and practical decision that will be based on numerous factors, ranging from aesthetic appeal to the precise heating demands of your property.
Whichever type of gas insert you choose, it’s important to consider whether a vent-free or direct-vent option is best for you and your family. While vent-free models offer convenience and a hassle-free installation, many still feel they aren’t as safe as they ought to be, whatever option you go for, bear in mind that brand reputation and user reviews should not be overlooked.
If you live in a property without a gas supply, then you may also want to consider an electric fireplace, or if you live in a rural location a pellet stove or wood stove may be more appropriate.
Finally, ensure you are choosing a model that offers the latest innovative features, including electric ignition and a fan system to circulate the heat evenly throughout your home. You are sure to find gas fireplace inserts with a low price tag, but this may be a false economy in the long term.
About the Author
Dave Miller is a HVAC technician with over 10 years in the industry. Dave created HeatTalk with the ambition for it to become a resource for individuals looking for answers, whether they be a layman, student or a professional.