Convert to Gas Insert
A gas insert transforms your wood-burning fireplace into a clean, efficient heat source you can ignite with the flip of a switch. You eliminate ash cleanup, chimney creosote, and indoor air quality concerns while gaining precise temperature control and realistic flames that rival the real thing.
Time Required
1-2 days
Cost
$3,000-$8,000
Difficulty
Hire a Professional
Gas Insert Types Compared
- Direct vent insert ($3,000-$6,000 installed): The most popular choice. Draws combustion air from outside and exhausts through a co-axial vent pipe up the chimney. Sealed glass front keeps combustion gases out of your living space. Up to 85% efficient.
- Vent-free insert ($1,500-$3,500 installed): No venting required, so all heat stays in the room. Uses an oxygen depletion sensor for safety. Not legal in all states and municipalities. Adds moisture to the air. Best as supplemental heat only.
- B-vent insert ($2,500-$5,000 installed): Uses existing chimney flue for venting. Draws combustion air from inside the room, making it less efficient than direct vent. Good option when chimney modification is impractical.
- Log set vs. full insert: A gas log set ($500-$1,500) sits inside your existing firebox and is the cheapest option but provides minimal heat. A full insert is a sealed, insulated firebox that slides into the opening and delivers real heating power.
Installation Process
Run a gas line to the fireplace
A licensed plumber or gas fitter runs a dedicated gas line from your main supply to the firebox. This typically costs $300-$800 depending on distance. The line must be properly sized for the BTU output of your chosen insert and pass a pressure test before use.
Install the vent liner
For direct vent inserts, a flexible aluminum or stainless steel liner is fed down the existing chimney. This co-axial liner contains both the exhaust flue and the fresh air intake. The old damper is either removed or permanently fixed open to accommodate the liner.
Set the insert into the firebox
The insert slides into the existing masonry opening. Insulation is packed around the unit to prevent heat loss into the chimney cavity. The surround panel covers any gaps between the insert and the fireplace opening. A licensed technician connects the gas line and tests for leaks.
Final testing and inspection
The installer performs a combustion analysis to verify proper venting and gas pressure. Many municipalities require a permit and inspection for gas appliance installations. Test the ignition system, thermostat or remote control, and blower fan before signing off.
Choosing the Right Size
- Measure your firebox opening: Width, height, and depth determine which inserts physically fit. Most inserts need a minimum opening of 28" wide, 20" high, and 14" deep.
- Match BTU output to room size: A 20,000 BTU insert heats roughly 1,000 square feet. A 35,000 BTU unit handles 1,500+ square feet. Oversizing leads to short cycling and wasted gas.
- Consider the flame aesthetics: Higher-end models use ceramic fiber logs and multi-colored flame burners that closely mimic a real wood fire. Budget models may look more obviously artificial.
- Blower fan option: Most inserts include a built-in blower to push heated air into the room. Variable-speed blowers let you balance heat output with noise level.
Pro Tips
- •Get the gas line done during rough-in: If your renovation involves open walls, run the gas line while framing is exposed. Fishing a gas line through finished walls costs 2-3x more.
- •Add a battery backup ignition: Electronic ignition inserts won't work during a power outage. Choose a model with a millivolt (standing pilot) system or battery backup so you have heat when you need it most.
- •Budget for the surround separately: The insert manufacturer's surround panel is functional but basic. Your new tile or stone surround (installed in the previous step) should be designed to frame the insert beautifully.