How a Fireplace Insert Saves Money and Adds Heat

An open masonry fireplace is a pleasure and a heating mistake. The U.S. Department of Energy puts it bluntly: traditional open masonry fireplaces should not be considered heating devices, because they draw as much as 300 cubic feet a minute of heated room air for combustion and send it straight up the chimney. A fireplace insert is a sealed, efficient stove built to slide into that opening and use the same chimney with a liner. It turns the room’s biggest heat leak into its heat source, and that is where the money is.

Where the savings come from

1. The fire stops pulling your furnace’s air up the chimney. An insert burns behind glass with its own controlled air supply. The warm air in the room stays in the room.
2. The fuel does real work. The DOE describes new catalytic stoves and inserts at efficiencies up to 83 percent (higher heating value) and advanced non-catalytic units at 65 to 75 percent. The Lopi Answer NexGen-Hybrid stove we sell is rated by Lopi at up to 80 percent HHV, and its insert twin is built the same way. An open fireplace is, in the DOE’s words, an energy loser. Same cord of wood, several times the heat in the room.
3. Zone heating. On the evenings the insert is lit, the room you live in is warm from the fire and the thermostat can sit lower for the rooms you are not in. How much that saves depends on how often you light it and how your house is laid out, which is why we do not print a number — but the logic is why inserts sell.
4. Gas inserts get the same effect without the wood. A direct-vent gas insert seals the old opening, vents through a liner and burns at the 70 to 85 percent efficiencies modern direct-vent units are rated at, on a thermostat or a remote. No wood to buy, season or carry.

Wood, gas or electric: which insert is which

• A wood insert is a stove without legs. It suits a house that has, or wants, a wood supply, and a masonry fireplace whose chimney can take a stainless liner. The Lopi Answer insert (a 1.4 to 1.5 cubic foot firebox that takes an 18-inch log and burns up to 8 hours, depending on the generation) is the small-firebox example; the Large Flush Wood Arch is the large one. Both are EPA-certified.
• A gas insert is the one most of our customers in the western suburbs choose: a sealed direct-vent firebox with a log set or a contemporary interior, a blower, a remote or a wall thermostat, and a yearly service instead of a chimney sweep. The gas fireplace benefits post covers the running of one.
• An electric insert is a plug-in flame effect with a small heater. It is the right answer for a condo, a bedroom or a fireplace whose chimney has been sealed, and the wrong answer if the goal is to heat a family room in January.

The gas versus electric post weighs the two in more detail; the fuel guide takes wood and pellet into account too.

What the installation involves

An insert is not a drop-in. A wood or gas insert in a masonry fireplace needs a stainless steel liner run the full height of the chimney: the old clay flue is the wrong size for it, and gas exhaust eats old clay tile from the inside. It needs a surround panel to close the gap between the insert and the opening, and for gas a supply line and, usually, an outlet for the blower. The chimney is inspected before we quote; a cracked crown, a damper that will not come out or a flue that is too small changes the job, and it is better to know at the estimate than on install day. Most inserts are installed in a day once the liner and the unit are on site; the written quote covers the unit, the liner, the gas or electrical work, the panel and the permit.

Is an insert worth it for your house?

It is worth it if you light the fireplace often and the room it is in is where you spend your evenings. It is not worth it if the fireplace is lit twice a year for the look. A good set of vented gas logs gives you the look for far less, and a glass door stops the open chimney draining the room when it is not lit. The free in-home estimate is where we say which one your house wants, and we will say “not an insert” when that is the answer.

One note on incentives: the federal tax credit for high-efficiency biomass stoves and inserts ended on 31 December 2025, so a wood insert bought now is bought on its own merits. Check with your utility for any current rebate on gas or electric equipment; those change from year to year.

Questions we get about inserts

Can an insert go into any fireplace?

Into most masonry fireplaces with a sound chimney, yes, sized to the opening. A factory-built (zero-clearance) fireplace is different: only inserts the maker lists for that firebox are allowed, and sometimes the honest answer is to replace the whole unit. The chimney inspection at the estimate decides it.

Does an insert need a chimney liner?

Yes. A wood insert needs a full stainless liner to draft properly and to keep creosote out of the old flue; a gas insert needs its own liner, or a pair of them, for exhaust and for combustion air. The liner is part of every insert quote we write.

How much heat does an insert put out?

A small wood insert like the Answer runs from about 12,000 to 60,000 BTU an hour; larger inserts go higher. A gas insert is sized to the room at the estimate, usually between 20,000 and 40,000 BTU. Either one will carry a large family room on its own on most winter evenings.

Can I keep burning wood in an open fireplace instead?

Of course, and many people do for the atmosphere. Just know that the DOE’s description — an energy loser that sends heated room air up the chimney — is the price of the open flame, and that a glass door, a top-sealing damper and dry wood make it less of one.

See one on the floor, then measure yours

Wood and gas inserts are on the floor at 1202-B 75th Street in Downers Grove. Bring the width, height and depth of your fireplace opening and a photo of the chimney, or book a free in-home estimate and we will measure and inspect it for you. Every insert we sell is installed and serviced by our own team.

Sources

• U.S. Department of Energy, Energy Saver: Wood and Pellet Heating — open fireplaces, inserts and stove efficiencies — energy.gov.
• Lopi Stoves: Answer NexGen-Hybrid specifications (BTU range, efficiency, firebox) — lopistoves.com.