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    Gas Fireplace Insert Buyer's Guide

    Do you want to upgrade your wood-burning fireplace, but don't want the stress that comes with a full renovation zone in your home? A gas fireplace insert might be your best choice! Designed to go into an existing fireplace, these appliances offer the best of both worlds.

    But, how do you know which insert is right for you? With dozens of manufacturers and models out there, eFireplaceStore is here to help you find the right one for your needs.

    What is a Gas Fireplace Insert?

    A gas fireplace insert is a unit that retrofits into an existing masonry fireplace. It does not matter which fuel the masonry fireplace was designed for originally. Wood-burning, coal-burning, and gas fireplaces can all be retrofitted with a fireplace insert.

    Fireplace inserts are more affordable. And, they serve as a less painless option than renovating a masonry fireplace. Additionally, a gas insert can burn either natural gas or liquid propane. Having options is great for people living outside the service areas of gas companies.

    Things to Know Before You Buy

    You should consider a few things before leaping into purchasing a fireplace insert. Some key things to consider include size, BTU output, and venting options.

    To find the correct size for an insert, you'll need to take a few measurements of your existing fireplace. You will need several numbers, so grab a tape measure. First, you need the height and width of the front opening of the fireplace. Then, you need to know how deep the fireplace opening is. Additionally, you need to know the height and width of the back wall of your fireplace.

    Now that you know the size of your existing fireplace, you can start to look at sizes of inserts. Doing this will give you an idea of what sort of insert you might like to have in your home.

    Fireplace Inserts vs Fireboxes

    A full fireplace insert has everything needed to replace your existing masonry construction. A firebox is just the metal enclosure where you will combust the fire. To install a firebox, you will need to buy gas logs, a burner, and other components separately.

    British Thermal Units (BTU)

    The BTU output of a gas fireplace insert is important as well. This ties in with the difference between getting a full fireplace insert or a firebox. The full gas insert will have a determined BTU output based on the fuel type. With a firebox, the gas logs and burner you select will determine the BTU output.

    You can easily determine the BTU output your home can accommodate. All you'll need are the measurements of the room where the insert will be installed. Next, multiply the L (length) x W (width) x H (height) x 20 to calculate the maximum BTUs your room can handle.

    It is up to you whether you decide to DIY the job or hire a professional. But, we recommend consulting an NFI certified technician to help with installation questions.

    Get Some Answers

    You'll want to be sure that a fireplace insert is the right way to go for your upgrade. First, ensure you have enough space to house the new unit. Also, note that some prefabricated fireplaces are not rated for use with inserts. So, check with your manufacturer to make sure your unit is rated for use with a gas insert replacement.

    Installing a gas fireplace insert requires work. There’s no way around it. Consider the gas venting you may have to run or the power lines you'll need for accessories. The possible challenges are endless. But, fitting issues, affected by the style of the gas insert, pose the most difficulty. That's why seeking the help of a certified expert is key to your installation success.

    Design Options

    Many brands offer various stylistic choices. But, most styles fit into one of two categories.

    Some inserts have a classic appeal while others speak to contemporary flair. There are large ones, small ones, and some sizes in between. You can even find ones that look more like a large flat-screen TV than a fireplace.

    You can add nice trimming around them for a more polished look. Simply put, there are too many design options to list here. So, it's best to narrow down the options by your desired aesthetic. Then, you can go from there.

    What about Venting?

    An insert has three main venting options. You can choose between vented and unvented. The choice often boils down to your heating needs, budget, and the available space. In this section, we'll cover these options in more detail.


    Factory-built ventless inserts burn cleanly. These unit are designed for a maximum of 40,000 BTUs for indoor applications. They are manufactured without a vent collar as they don't use venting systems. These units are highly efficient heating sources. And, many come with a blower to circulate heat throughout your home.

    As discussed earlier, gas fireplace inserts are installed into an existing fireplace. They are secured with fasteners. And, you can give them a more complete look with optional accessories. Some of the exterior accessories include trim kits, surrounds, or faceplates.

    These options cover visible space between the opening and the outer shell of the insert. We recommend choosing an insert that is as large as possible. You want to avoid downsizing your fireplace too much.

    But, be aware that some areas do not permit vent-free appliances. There are several reasons for this. The main debate centers functionality at higher altitudes and safety concerns. For these reasons, it is a good idea to review your local codes before choosing a vent-free unit.

    Direct Vent

    Direct-vent fireplace inserts are the least complicated of the options. With front sealed openings, they are good, all-around solutions. Direct-vent inserts operate with the same efficiency as direct-vent fireplaces. They use a venting method that's much different from traditional venting.

    Most direct-vent fireplace applications use coaxial chimney pipes. These include a pipe within a pipe - a smaller inner pipe encased by a larger outer pipe. It's a rigid system, designed to route vertically or horizontally through an exterior wall. Another venting method for these units include the co-linear vent systems.

    The co-linear design allows you to route your venting up an existing masonry chimney. Instead of a pipe within a pipe design, it includes two separate pipes. The pipes work in a similar fashion. One pipe draws combustible air from outside. The other pipe expels unwanted combustion particulates from the home through the chimney.

    Many systems rely on two 3-inch diameter liners. These connect to a purpose-built termination that must be installed at the top of the chimney. The termination system keeps the intake air and exhaust air separate. It also prevents water intrusion. As with vent-free systems, direct-vent models are designed with efficiency in mind. They, too, feature a built-in blower system to maximize heat transfer.

    Natural Vent

    Often referred to as B-Vent, this venting method is the closest to a wood-burning fire. B-Vent fireplace inserts have an open-face flame and venting system. They provide a realistic flame without the maintenance needed for a wood-burning unit.

    B-Vent inserts have low heating efficiency. This is because they lose much of the produced heat to the chimney. Most people install these units for aesthetic appeal as opposed to heating ability. This type of insert requires a flexible vent system that is routed through a masonry chimney.

    Installation Considerations

    Before installing any gas insert, you'll also want to consider the gas line logistics of your home. Of course, you can choose between natural gas or propane. But, you will need a gas line. If you don't have one for your existing fireplace, you'll need to have one installed. You'll also need to determine the best point of entry for your unit.

    Many prefabricated fireplaces have knockout areas. These appear within the fireplace opening or on the exterior of the fireplace jacket. Either space allows for the passing of a gas line into the fireplace. If the fireplace doesn't have a gas line in place, the installer may need to open an adjacent wall to route one.

    For masonry fireplaces, it is possible to bore a hole with a masonry drill. This will allow you to route an external line into the opening of the insert. Each installation is different. So, we suggest discussing the time and cost of routing a gas line with a seasoned plumber.

    You'll also want to consider any electrical components. Units that use a blower, internal lighting, or an electronic ignition system will need electricity. You can either use a nearby electrical outlet or install one.

    For an existing outlet, you can route a low-profile electrical feed wire along the baseboard and into the fireplace opening. An electrical Panduit will help keep wires hidden from view. For a cleaner look, you can install an electrical outlet inside the fireplace opening. This option will need routing similar to that of a gas line.

    Venting Components

    To complete the installation of vented models, you will need flexible aluminum liners. Most manufacturers offer a purpose-built vent kit that includes these. Vent kits include universal components that meet the UL listing requirements.

    Most liners for fireplace inserts will be collapsed for shipping. So, you'll need to expand them fully before installing. Also, take careful note of how the flue collar on the insert and the flue collar on the fireplace align. Unlike a masonry fireplace, there is usually no smoke chamber to accommodate venting offsets.

    The ceiling of a firebox is usually flat. And, there is often less than six inches of space between the insert and the fireplace. So, it will not be possible to offset the chimney liners enough to route them into the chimney.

    The owner's manual for each unit will show the measurement from the face of the fireplace insert to each flue liner. Take this information into account to make sure the vent collars and chimney opening overlap for tight installations.

    The actual installation of the gas fireplace insert should be done by a licensed professional. Some manufacturers require professional installations to validate the warranty of their products.

    Completing the Look

    Many times, installing a fireplace insert will result in a gap between the edge of the insert and the fireplace opening. A surround can and is often required to cover this gap. A surround covers the gap between the edges of the insert and the fireplace opening.

    This surround could be a multi-panel unit or a single piece. You'll need to verify that the surround is large enough to cover the fireplace opening. But, it should not be so large that it looks awkward or does not fit within the confines of a mantel or surround. Most models have several surround options.

    Not all fireplace surfaces are smooth. In such cases, it can be a challenge to make a surround sit flat against uneven surfaces or ledges. You'll want to create a smooth surface for the surround or to trim.

    If the surround cannot be trimmed, it is possible to overlay the surround against the face of the fireplace and trace where the surround will sit. Then, you can use castable mortar to create a skim coat over the stone to create a smooth surface.

    Some Top Manufacturers in the Industry

    • Napoleon — Started in 1976 as a steel fabrication business, Napoleon gained solid ground in the industry after creating the first single-pane ceramic glass stove door. From there, the manufacturer progressed into fabricated fireplaces. They introduced innovative log designs and industry-leading manufacturing techniques.
    • Empire — A family-owned business since 1911, Empire has produced quality gas-fired hearth products for decades. Offering a range of high-quality products, Empire fireplaces are known for simplicity, ease of use, and longevity.
    • Kozy Heat — After ongoing fuel gas embargo, Kozy Heat began manufacturing high-efficiency wood-burning appliances in 1976. They later transitioned into producing gas-fueled models. Today they produce a diverse line of gas fireplace inserts that are built to a very high standard.
    • Kingsman — Kingsman started producing wood-burning appliances in 1976 before transitioning into gas models in 1983. They have since developed a highly customizable range of gas inserts fit for any style. Focused on a low volume of quality products, Kingsman has one of the lowest failure rates in the industry.

    Shipping Information

    Most fireplace inserts will arrive on a pallet via LTL freight. The freight company will call you to schedule a delivery to your home or business. But, these deliveries often require more than one person to receive the package. Upon arrival, we encourage customers to inspect their products carefully for damages. Some manufacturers have limited warranties.

    Care and Maintenance

    To keep your unit in good running condition, it's important to perform ongoing maintenance. To help, we've established a list of tips to help keep your fireplace insert operating for a long time. Among those things that should be done on a regular basis are included on the chart.

    Have the insert checked out by an NFI certified technician at least once a year. Ideally, this inspection should take place around September or before the start of the cold season. Doing this will ensure that your insert is operating efficiently. It also helps prevent problems or issues or catch those that are present or in need of addressing.

    Ways to Extend the Lifespan of Your Insert

    If well maintained, a gas fireplace insert can last between 15-20 years. To get the most years out of your unit, make sure to follow the manufacturer guidelines. It is here that you'll find specific maintenance needs for your unit.

    But, all inserts are vulnerable to water. So, you'll want to make sure the chimney is sealed against moisture intrusion. Water exposure could lead to premature corrosive damage to the unit.


    No matter which fireplace insert you choose, we hope this article provided some helpful information to make your decision easier. If you're looking for a cleaner burn with less ongoing maintenance, you're looking in the right place.

    Remember, a gas fireplace insert saves you from regular sweeping and ash buildup that comes with a wood-burning unit. And, depending on the venting you select, it could also save you money. Grant yourself permission to indulge in a more efficient and cost-effective option.

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    Gas Fireplace Inserts Q&A with the NFI Certified Specialists

    * Please Note: All customer questions are answered by our NFI Certified Specialists free of charge!
    5 Questions & 5 Answers
    from WA asked:
    September 7, 2017
    How do I proceed with installation?
    1 Answer
    For gas inserts and log sets, we typically recommend contacting local plumbing and heating/air conditioning companies, most of which staff gas fitters/technicians that can do the installation work.
    Submitted by: Tyler M. on September 7, 2017

    from Norwalk, CT asked:
    October 12, 2016
    How do I know what size to get?
    1 Answer
    To determine size, you will need the front width, rear width, depth, and height, as well as whether you will be using natural gas or propane. From there, we can assist you.
    Submitted by: Brennan W. on October 12, 2016

    from Beaverton, OR asked:
    October 2, 2016
    What is the measurement that determines size?
    1 Answer
    It is the width measurement that narrows down the overall search results.
    Submitted by: Chris C. on October 3, 2016

    from Winchester, VA asked:
    January 9, 2016
    What is the difference between vented and vent free propane gas fireplace inserts?
    1 Answer
    Vented fireplace inserts will generally be sealed with a pane of glass and use a pair of 3 or 4 inch liners that are routed up the chimney. One liner will pull combustion air from the outdoors, while the other will vent exhaust gases. The vented systems do not effect air quality. Vent free units are completely sealed from the chimney and vent all heat into the room. The are carefully built to avoid off gassing of dangerous byproducts into the room, but consideration must be made on room size and location.
    Submitted by: eFireplaceStore on January 11, 2016

    from Milford, CT asked:
    September 28, 2013
    How do I size an insert?
    1 Answer
    Our site organizes our insert options by width measurement. However, to properly fit an insert for you, we would need the front width, rear width, depth and height of your fireplace.
    Submitted by: Kevin E. - NFI Certified Specialist on September 28, 2013

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