Fireplace Insert Installation Cost Calculator
An insert slides into a firebox you already have — so the math is short: the appliance, the flue liner it must have, and labor. Skip the liner and you have a smoke problem, not a savings.
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An insert turns a drafty open fireplace into an efficient wood or gas appliance — it slides into the existing firebox and MUST have a properly sized liner up the flue (see the liner tools). About $4,400 here.
An insert is the fix for the drafty open masonry fireplace that dumps your heat up the flue. It is a sealed firebox — wood or gas — that you push into the existing opening and run efficiently. The reason it earns its keep is the same reason it needs a liner: a sealed appliance breathes through a flue sized to its outlet, usually 6 inches, not through the cavernous masonry flue built for an open fire.
That is the line most cheap quotes "forget". A properly sized, ideally insulated liner run from the insert to the chimney top is not an upsell — it is how the appliance is listed to operate. Vent an insert into an oversized bare masonry flue and the gases cool, draft stalls, and creosote piles up fast. So this estimator refuses to let the liner go to zero in spirit: keep it in the bid, sized right (use the flue-liner-size tool to confirm the diameter).
Formula
total = (insert + liner + labor) × (1 + contingency)
Three buckets, because an insert install genuinely has three. The insert includes its decorative surround panel that hides the gap to the old opening. The liner is length × a per-foot rate plus insulation — price that separately with the liner-cost tools and drop the number in here. Labor is the fit-and-connect: pull the old damper, run the liner, seal the block-off plate, set the surround.
Worked example
Converting a 1980s open masonry fireplace to a wood-burning insert. Insert with a black surround at $2,640, a 22-ft insulated 6-inch stainless liner at $915, and labor to set it and build the block-off plate at $780. With a 10% buffer:
(2,640 + 915 + 780) × 1.10 = 4,335 × 1.10 = $4,769
A gas insert instead of wood swaps the liner detail for a gas line and a co-axial vent, which nudges labor up — but the shape of the estimate is the same.
What people leave out (and pay for later)
- The liner, sized to the insert. Match the appliance outlet, not the old flue. A liner smaller than the outlet chokes it; a bare oversized flue runs cool and glazes. Insulate it and the draft is stronger and the creosote slower.
- A block-off plate. Sealing the old damper throat around the liner stops the room from losing heat up the dead air space. Cheap to do during the install, annoying to add after.
- Fireplace condition. An insert does not fix a cracked firebox or a leaking crown — those get repaired first. A quick Level 2 look before you buy saves an ugly surprise.
- Clearance to the mantel and trim. Combustible mantels and surrounds have listed clearances; a deep mantel may need a shield or a shim.
The Chimney Safety Institute of America is the reference for who should be running that liner and inspecting the flue.
Reference table
Labeled planning band — a sanity check, NOT a quote. The liner alone can be a big share; confirm with a CSIA-certified installer.
| Job | Typical band |
|---|---|
| Fireplace installation | $1,500 – $8,000 |
| Reline / new liner | $1,500 – $5,000 |
Frequently asked questions
Do I really need a new liner for an insert?
Yes. A sealed insert is listed to vent through a flue sized to its own outlet — almost always a 6-inch liner run to the chimney top, ideally insulated. Venting it into the big bare masonry flue leaves the exhaust cool and sluggish, which stalls draft and builds creosote. Treat the liner as part of the appliance, not an option.
Wood insert or gas insert — does the cost differ?
They land close on the appliance, but the venting detail differs: a wood insert needs a full liner up the flue, a direct-vent gas insert needs a co-axial vent and a gas line. Labor shifts accordingly. Enter whichever venting your quote lists in the liner line and adjust labor.
Can I put an insert in any fireplace?
Only a sound one. The firebox and flue have to be in good shape and big enough for the insert and its liner. Have a cracked firebox or a leaking crown repaired first — an insert covers the opening, it does not cure the masonry behind it.
What is a block-off plate and why does it matter?
It is a sealed panel that closes the old damper throat around the new liner so room air stops leaking into the dead space above the insert. It is a few dollars of sheet metal and sealant during the install and a real efficiency gain — insist on it.