Fireplace Insert Installation
Why this matters
Fireplace inserts convert a low-efficiency masonry fireplace (10 - 15% efficiency) to a 70 - 85% efficient heater. Customer benefit: real heat output + dramatic fuel cost reduction. Service price. Chimney sweep companies are the natural installer - they have the chimney inspection expertise + the ladder + the customer relationship. Adding insert installation transforms a sweep route from service calls to + installs.
What an insert is
A fireplace insert is a closed-combustion heater that fits INSIDE an existing masonry fireplace. The firebox of the insert sits inside the existing firebox; the insert flue connects to a chimney liner (typically stainless steel) that runs up the original chimney.
Three insert categories:
Wood-burning insert - the classic upgrade
- Closed catalytic OR non-catalytic combustion
- EPA-certified (2020+ Phase II)
- 70 - 80% efficiency typical
- 30,000 - 75,000 BTU/hr output
- Customer reloads + tends fire
Gas insert - convenience-focused upgrade
- Direct-vent OR vent-free (mostly direct-vent residential)
- 80 - 85% efficiency
- 20,000 - 40,000 BTU/hr output
- Thermostat OR manual operation; no tending
Pellet insert - efficiency + convenience hybrid
- Pellet hopper; auger feeds combustion chamber
- 70 - 80% efficiency
- 20,000 - 60,000 BTU/hr output
- Customer loads hopper (typically once daily)
- Less common; specialty install
Pre-install requirements
Existing fireplace inspection
- Masonry condition: cracked tile liner, spalled brick, deteriorated mortar
- Damper functional
- Smoke chamber adequate
- Hearth condition
- Crown + cap on chimney
- Photos + measurements
Chimney + flue inspection
- Level 2 inspection (camera scope of full flue)
- Existing lining condition
- Damage requiring repair BEFORE insert install
- Sizing: existing flue + planned liner
Insert sizing
- Match insert opening to existing fireplace opening
- Standard insert openings: 36" × 28" (small), 42" × 32" (medium), 48" × 32" (large)
- Liner inside diameter typically 6" for wood, 4-5.5" for gas
- Heat output matched to space (BTU/hr per heated sq ft)
Customer briefing
- Existing fireplace look will change - insert front visible
- Some inserts have "blower" fans for heat distribution (some quiet, some noticeable)
- Wood insert: customer manages wood, ash removal, periodic chimney sweep
- Gas insert: customer manages gas supply, annual service
- Cost comparison vs. continued use of old fireplace (savings demo)
Installation procedure (wood-burning insert)
- Site prep: cover hearth + flooring; clean existing fireplace
- Chimney liner: stainless from top of chimney down to insert; insulated wrap; rain cap (see Chimney Lining Install SOP)
- Damper: remove OR permanently fix open; insulate around opening
- Position insert: 150 - 400 lbs (helper + moving equipment); level + plumb; connect flue collar to liner with high-temp silicone
- Hearth + surround: manufacturer trim kit; hearth extension (16 - 18" combustible-free zone in front of wood inserts)
- Electrical (blower-equipped): hardwired OR plug-in 120V per spec
- Test fire: break-in low-heat first 3 - 5 fires; verify draft + no spillage + no leaks
- Customer handoff: operation + wood seasoning + cleaning + annual sweep commitment + warranty
Installation procedure (gas insert)
Similar to wood, with these differences:
Step 3: Gas supply
- Confirm gas type (natural OR propane)
- Gas line sized + routed to fireplace
- Drip leg + shut-off valve within reach of insert
- Pipe-thread sealant rated for gas; soap-test all fittings
Step 4: Direct vent (most modern installs)
- Coaxial vent: small pipe inside larger pipe; one carries combustion gas OUT, the other brings combustion air IN
- Vent rises through chimney; specific length + termination per manufacturer
- Some installs allow direct exterior wall vent (chimney NOT required)
Step 5: Electrical (most gas inserts have battery backup + electric controls)
- Hardwired 120V for blower + controls
- Battery backup for thermostat-controlled units
Step 6: Test fire
- First-fire procedure per manufacturer
- Verify pilot light + main burner ignition
- Flame appearance (typically yellow / orange with logs visible)
- No leaks (final soap test)
- Carbon monoxide reading at the insert area + room
Common installation mistakes
Insufficient liner insulation
- Cold liner = creosote condensation
- Wood insert with poorly-insulated liner builds creosote fast = chimney fire risk
Wrong damper handling
- Damper left functional + customer closes it during fire = smoke into room
- Damper fully removed + customer can't seal flue when not in use = energy loss
Wrong-size insert for fireplace
- Insert too large = won't fit; insert too small = poor seal + gaps
- Measure carefully; verify manufacturer fit
Skipped hearth extension
- Combustible-free zone in front of wood inserts mandatory
- Without it, customer's flooring catches fire
- 16 - 18" minimum; some insurers want 24"
No annual service plan
- Customer doesn't sweep / inspect annually = chimney fire risk
- Sell annual service contract at install; recurring revenue
NEVER install a fireplace insert without confirming the chimney has been PROFESSIONALLY INSPECTED + lined OR re-lined. The old masonry chimney with deteriorated clay tile + a brand-new insert is a CHIMNEY FIRE waiting to happen. Hot combustion gases from the closed-combustion insert hit cracked tile, leak into the brick, ignite creosote built up in cracks. Customer's home burns down. Always quote the chimney inspection + lining as a package WITH the insert - never as an optional add-on. Insurance carriers + state codes increasingly require this.
Permits + inspection
- Building permit + mechanical permit typically required
- Gas permit for gas inserts
- Final inspection by AHJ
- Customer's home insurance may require post-install inspection certificate
- Maintain manufacturer warranty by certified-installer requirement
Annual service contract
- Premium contract: bundle with sweep, inspection, repairs at preferred rate
This is the recurring revenue tail of insert install.
References
- NFPA 211 (Standard for Chimneys, Fireplaces, Vents + Solid Fuel Burning Appliances)
- NFPA 54 (gas appliances)
- CSIA (Chimney Safety Institute of America)
- Manufacturer install manuals
- Local building + mechanical codes
- Manuall internal: Chimney Liner Installation, Annual Chimney Inspection SOP