Fireplace Inserts: The Complete Guide to Types, Liners, Installation, Cleaning and Cost

Three terms get mixed up:

• Fireplace insert. A heater designed to be installed inside an existing fireplace. It has a surround (decorative panel) that covers the gap between the insert and the fireplace opening. Wood and pellet inserts are listed as room heaters (UL 1482 for solid fuel, ASTM E1509 for pellet, which is the test standard the IRC references for vented pellet room heaters in Section M1410).
• Fireplace stove / hearth stove. A freestanding stove that sits in front of or partly inside the fireplace and connects to the chimney. The IRC (Section M1414) requires fireplace stoves to be listed to UL 737 and installed per their listing.
• Zero-clearance (factory-built) fireplace. A complete metal fireplace built into a wall with its own listed chimney, tested to UL 127 under IRC R1004.1. Some inserts are also listed for installation into specific factory-built fireplaces, but many are not; see the section on factory-built fireplaces below.

Sources: DOE Energy Saver; HomeGuide 2026 pricing for wood stove inserts ($1,200–$4,000), pellet inserts ($1,500–$4,500 unit, $2,500–$7,000 installed), wood stove installation ($3,000–$8,000 typical; $4,000–$8,000 into an existing masonry chimney), electric fireplaces ($200–$3,000 installed), gas line runs ($350–$2,000) and venting systems ($200–$3,000); Angi 2026 for gas and pellet service. Ranges are estimates and vary with local labor costs.

Wood-burning inserts

Definition. A wood stove built to fit a fireplace opening, with a sealed door, a baffle or catalyst, and usually a blower that pushes warm air out of the top of the surround.

How to identify it. A heavy steel or cast-iron box set into the firebox with a flat surround panel, a loading door with glass, an air control, and often a blower switch. There will be an EPA label, often on a pull-out tag or on the insert body (sometimes only visible when the surround is removed).

Typical cost. $1,200–$4,000 for the unit; $3,000–$8,000 installed in an existing masonry chimney with a new liner (HomeGuide 2026).

When it applies. Homes where the owner wants real heat from an existing masonry fireplace and has access to firewood. It is the most common retrofit in colder regions.

Venting. A stainless steel liner sized to the insert's flue collar, commonly 6 inches for modern units. Chimneys.com notes that modern high-efficiency stoves typically use flues of 5.5 or 6 inches, much smaller than the original fireplace flue.

Gas inserts

Definition. A gas burner and ceramic log or media set inside a sealed metal firebox with a fixed glass front.

How to identify it. Fixed glass that does not open for loading, a control panel behind a lower grille, a gas shut-off valve, a pilot or electronic ignition, and a wall switch, thermostat or remote.

Venting. Most gas inserts sold today are direct-vent: they draw combustion air from outdoors and exhaust outdoors through a sealed system. In a masonry chimney this is usually two flexible liners run side by side (one intake, one exhaust, called co-linear) or a pipe-within-a-pipe (co-axial or concentric), exactly as the insert manufacturer specifies.

Glass safety barrier. Since January 1, 2015, gas fireplaces, stoves and inserts built to the ANSI Z21.88 and Z21.50 standards must ship with a barrier screen if the glass can exceed 172°F (see our gas fireplace service guide).

Typical cost. Wide range by model and by gas line length; HomeGuide lists gas line runs at $350–$2,000 and venting systems at $200–$3,000 on top of the appliance.

When it applies. Owners who want push-button heat with no wood handling, and homes in areas with wood-burning restrictions.

Pellet inserts

Definition. A pellet stove body shaped to fit a fireplace. A hopper (usually at the top or side) feeds pellets to a burn pot by an electric auger; a combustion blower pulls air through the fire and pushes exhaust out.

How to identify it. A hopper lid, a control panel with a thermostat or heat settings, and a power cord. Exhaust exits through a small (3- or 4-inch) pipe.

Venting. In a fireplace, the pellet vent or a stainless liner should run to the top of the chimney. The Harman pellet stove installation manual, for example, calls for a stainless liner (typically 4-inch inside diameter) in a masonry chimney that is cracked or has no clay tile liner, a steel plate sealing the damper area, and notes that some regional codes require the vent to extend to the chimney top (Harman XXV manual).

Typical cost. $1,500–$4,500 for the unit; $2,500–$7,000 installed (HomeGuide 2026).

When it applies. Owners who want thermostat control, low emissions and fuel that comes in bags, and who are home daily to fill the hopper. Pellet inserts need electricity, so plan for power outages.

Electric inserts

Definition. A resistance heater with a fan and an LED or projected flame effect in a firebox-shaped box.

How to identify it. A power cord or junction box, no gas line, no vent.

Venting. None. The chimney should be capped and the damper closed or the flue sealed to stop heat loss and drafts. A standard 120-volt, 1,500-watt heater produces about 5,100 BTU per hour.

Typical cost. $200–$3,000 for electric fireplaces installed (HomeGuide 2026).

When it applies. Condos, rentals, homes with damaged chimneys the owner does not want to repair, and areas with strict wood-burning rules. Note that an electric insert in a fireplace whose chimney is still open to the weather does not stop water, animal or masonry problems; the chimney still needs a cap and periodic inspection.

A fireplace flue is sized for an open fire, which needs a huge volume of air. A typical masonry fireplace flue might be 8 x 12 or 12 x 12 inches (nominal), while a modern wood insert has a 6-inch round collar. Connect the small collar to the big flue and the exhaust slows, cools and condenses into creosote. That is the physics behind every liner rule below.

The three ways inserts get connected

What the manuals say. The Pacific Energy insert installation manual is a good representative example. It lists two acceptable US methods, a full flue liner "where a stainless steel rigid or flexible liner extends from the Insert flue collar to the top of the chimney" and a positive flue connection "where a throat blocker plate and a short connector pipe is used", while stating that a full liner is required in Canada and that the company "highly recommends the use of a full liner as the safest installation." It also requires a minimum 15-foot chimney height for that model and says the existing fireplace damper must be locked open or removed. Your insert's manual is part of its listing, so the installer must follow it line by line.

Why many sweeps insist on a full liner anyway. Beyond creosote, a full liner:

• Matches the flue to the collar, which improves draft and start-up.
• Keeps the flue warmer, especially in exterior chimneys.
• Makes cleaning possible without pulling out an insert that can weigh several hundred pounds.
• Seals a clay tile flue with cracks or missing mortar joints, which would otherwise fail inspection.

Slammers in older homes. Inserts installed in the 1970s and early 1980s were often slammers. If a home inspector or sweep reports "no liner" or "insert not connected," expect a recommendation to stop using the insert until a full liner is installed. Removing the insert usually reveals creosote packed in the smoke chamber and on the smoke shelf.

Liner materials and insulation

Many homes built since the 1980s have a metal factory-built fireplace, not masonry. Inserts can go into these only when:

1. The insert is listed for installation in factory-built fireplaces, and
2. The fireplace manufacturer permits it (many fireplace listings name approved inserts or require specific modifications), and
3. A full liner runs through the factory-built chimney. The Pacific Energy manual, for example, specifies a 6-inch stainless rigid or flexible liner for factory-built fireplace installations.

Removing or cutting fireplace parts (smoke shields, refractory panels, damper) to make an insert fit usually voids the fireplace listing unless the manual allows it. For gas logs specifically, the IRC (R1004.4) prohibits unvented gas log heaters in factory-built fireplaces unless the fireplace system has been tested, listed and labeled for that use under UL 127. See our prefabricated chimneys guide.

Sizing has two parts: will it fit, and how much heat do you need.

Fit. Every insert lists minimum fireplace opening dimensions. The Pacific Energy insert manual, for instance, requires a minimum front width of 30-5/8 inches, rear width of 22-1/4 inches, height of 21 inches and depth of 18 inches. Measure:

• Front width at the opening
• Rear width at the back wall of the firebox
• Height from hearth to the lintel
• Depth from the front face to the back wall, and depth at the top (sloped back walls reduce usable depth)
• Hearth height relative to the room floor

Heat. DOE's Energy Saver gives a rough rule: a 60,000 Btu stove can heat about 2,000 square feet and a 42,000 Btu unit about 1,300 square feet. In practice the right size depends on climate, insulation, ceiling height and layout. A fireplace in a closed-off living room cannot push heat to a distant bedroom wing no matter how big the insert is, and an oversized wood insert gets run at low air settings, which makes creosote. Talk through your floor plan with the dealer.

Chimney. Check the insert's minimum chimney height and liner diameter. A short chimney on a one-story house, or a chimney shared with other flues, may need a taller liner or a different appliance.

Clearances and hearth protection

Inserts sit close to wood mantels and trim, so the manual's clearance table matters as much as the stove's. The Pacific Energy example lists 24 inches to a mantel and to top facing, 6.5 inches to side facing and 20.5 inches to an adjacent side wall. The IRC's baseline hearth extension for masonry fireplaces (R1001.10) is at least 16 inches in front and 8 inches beyond each side for openings under 6 square feet, and 20 inches in front and 12 inches beyond each side for larger openings. Many inserts need additional floor protection with a specific insulating value when the hearth is low, so check the manual before you buy.

This is how a professional installation of a wood or pellet insert into a masonry fireplace normally runs. Gas inserts follow the same pattern with gas line work added.

1. Pre-installation inspection. The CSIA advises having a certified sweep inspect the chimney before any new hearth appliance is installed, looking at the old and new appliance types, obstructions and creosote, flue size, liner condition, chimney height for draft and the air-tightness of the house (CSIA). A change of appliance is a standard trigger for a Level 2 inspection with a camera.
2. Sweep the fireplace and flue. The existing flue and smoke chamber are cleaned so the liner can be dropped and so old creosote is not left behind the new insert.
3. Permit. The installer or homeowner pulls a mechanical or building permit where required (see below).
4. Measure and order. Fireplace dimensions, chimney height from the hearth to the top of the crown, and flue tile size decide the liner length, diameter and insulation type.
5. Prepare the fireplace. The damper is removed or locked fully open, per the manual. Loose firebrick or smoke-chamber parging is repaired. Some installers seal the throat with a steel block-off plate and insulation.
6. Install the liner. The liner is lowered from the roof, often with a pulling cone, and connected at the bottom to the insert's connector or adapter. Insulation is wrapped or poured where required. A top plate seals the crown and a stainless cap goes on top.
7. Set the insert. The insert is slid in on its rails, connected to the liner (often while the insert sits partly out of the fireplace), leveled and pushed into place.
8. Surround and blower. The surround panel is fitted, the blower wired (usually to a 120-volt outlet), and the hearth protection checked.
9. Clearance and hearth check. Mantel, trim and side walls are measured against the manual; hearth extension size and insulating value confirmed.
10. First fire and training. The installer runs a break-in fire and walks you through air controls, bypass or catalyst operation, fuel quality and ash disposal.
11. Final inspection. The building inspector signs off the permit; keep the permit, the manual and the installer's paperwork.

• Permits. Most US jurisdictions require a permit to install a wood, pellet or gas insert, to install a chimney liner, or to run a new gas line. HomeGuide lists permits for wood stove installations at about $100–$500 and for pellet stoves at about $50–$100. DOE's Energy Saver tells homeowners to contact the local building codes department before installing.
• Gas work. Gas line work is typically done by a licensed plumber or gas fitter, depending on the state.
• Emission rules. New wood and pellet inserts must be EPA certified to the 2020 standard. Some state and local air agencies restrict wood burning on poor-air days or ban new wood-burning devices in new construction; check before choosing a wood insert. DOE notes that some municipalities restrict or ban wood-burning appliances.
• Insurance. Tell your homeowners insurer about a new solid-fuel appliance. Some ask for proof of professional installation or a permit final.
• Home sale. An insert with no liner, or with a liner that is not documented, often triggers a Level 2 inspection request from buyers. See chimney inspection for home sales.

How an insert is connected decides how it gets cleaned.

In-place cleaning (full liner)

With a full-length liner, the sweep usually:

1. Removes the insert's baffle (and catalyst if present) so the flue collar is open.
2. Sweeps the liner from the roof down with a brush sized to the liner, or from below with rods.
3. Vacuums the debris that falls into the insert's firebox.
4. Cleans the cap and checks the top plate seal.
5. Inspects the liner with a camera if there is any doubt about its condition.

Time: usually 1–1.5 hours. Cost: typically the standard sweep range, $150–$400 depending on height and roof access.

Pull-out cleaning (positive connection or unknown connection)

When the insert connects only to the first flue tile, creosote builds in the smoke chamber and on the smoke shelf behind the insert, where it cannot be reached from the firebox. The sweep must:

1. Disconnect power to the blower and remove the surround.
2. Slide the insert forward on its rails or on a dolly (inserts are heavy; many sweeps bring a second tech).
3. Disconnect the connector, sweep the connector, smoke chamber, smoke shelf and flue.
4. Reinstall, reconnect and reseal the block-off plate.

Time: often 2–3 hours. Cost: an estimated $250–$500+, because of labor and the risk of damaging hearth tile. Many sweeps will quote a full liner instead of repeated pull-outs, and over several seasons the liner can offset much of its cost in avoided pull-out fees and creosote treatments.

Insert cleaning checklist

• Connection type confirmed (full liner, positive connection or none)
• Baffle, blanket and catalyst removed and inspected
• Liner swept full length; cap and screen cleaned
• Top plate sealed at the crown; no gaps for rain or animals
• Liner-to-insert connection tight and fastened
• Smoke chamber and shelf checked (pull-out or camera) for hidden creosote
• Door and glass gaskets tested; glass clean and uncracked
• Blower cleaned of dust and pet hair (a clogged blower overheats the insert)
• Surround sealed to the fireplace face
• Clearances to mantel and trim checked against the manual
• Pellet inserts: burn pot, heat exchanger tubes, ash traps and combustion fan housing cleaned
• Gas inserts: burner, logs, pilot assembly, glass gasket, vent terminations checked; CO test at the face
• Written report and photos provided

HomeGuide's 2026 fireplace data puts typical hourly operating costs at about $0.70 for natural gas, $2.30 for propane and $0.15 for electric fireplaces, though actual costs depend on your appliance size and local energy prices.

All prices are estimated ranges from 2026 national cost surveys; local labor rates, chimney height, roof pitch and access move them up or down.

• Wood inserts: burn wood with under 20% moisture (EPA), run a hot fire after each reload before turning the air down, and never run the insert with the door cracked open as a "fireplace."
• Blowers: vacuum the blower intake at least once a season. Dust and pet hair cut airflow and let the insert body run hotter.
• Catalytic inserts: DOE advises inspecting catalytic combustors about every 2 cords burned.
• Pellet inserts: use certified pellets (PFI, ENplus or CANplus); empty the hopper at the end of the season so pellets do not absorb moisture and rust the auger, as DOE recommends.
• Gas inserts: keep the glass barrier screen installed, have the vent terminations checked each year, and never run a vented insert with a blocked cap.
• All inserts: CO alarms near sleeping areas and on the hearth level (CDC guidance), and a fire extinguisher nearby.

Illustrative scenarios only, not real customers. Costs are estimated 2026 ranges based on national surveys adjusted for typical local labor.