Fireplace Insert Installation

What an insert changes

An open fireplace pulls a lot of room air up the chimney, and much of the heat goes with it. An insert is a closed firebox, made of steel or cast iron, that sits inside the existing fireplace. It burns with controlled air and puts more heat into the room. It also changes what the chimney has to do: the exhaust leaves through a much smaller opening, often at lower temperatures.

That is why the liner matters as much as the insert itself. Our guide fireplace inserts explained covers the theory.

Inserts also change how the room feels. An open fire throws radiant heat out the front. An insert heats its steel or iron body and often uses a blower to move warm air, so the heat spreads further into the room. Many owners say the room stays warmer long after the fire dies down.

Wood, gas or pellet

Whatever the fuel, the insert must be listed for installation in a fireplace and installed according to its manual. Each manual sets the minimum fireplace size, hearth extension and the liner it requires.

Why a full-length liner

Older installations sometimes connected an insert to the bottom of a large clay flue with a short pipe, or no pipe at all. Exhaust then spills into an oversized flue and smoke chamber, cools quickly and leaves heavy deposits where they are hard to clean. Most manufacturers now specify a liner connected to the insert and running to the top of the chimney. The insert's manual sets the size and type.

Read more on chimney liners.

A liner connected directly to the insert also makes cleaning easier. Deposits collect inside the liner, where they can be reached, instead of in the smoke chamber behind the insert, where they are hard to get to.

How we assess it

• We measure the firebox opening, depth and hearth to see which inserts fit.
• We check the damper and smoke chamber, which affect how the liner passes through.
• When the flue allows, a chimney camera checks the flue's condition and any offsets.
• When safe, we check the crown and chimney top, where the liner will end.
• For factory-built fireplaces, we check whether the manufacturer allows an insert at all.

You get our findings with photos and a clear list of what the installation will need before anything is scheduled. See also inspection before a new appliance.

Installation in outline

1. Prepare the chimneyClean the flue and smoke chamber and complete any repairs found during the assessment.
2. Install the linerRun the liner from the top and connect it to the insert's outlet, with insulation where the manual or flue size calls for it.
3. Set the insertPosition the insert and seal the opening with the surround.
4. Finish the topFit the top plate and cap.
5. Walk-throughShow you how the controls work and what maintenance the manual requires.

Limitations

An insert needs enough firebox space and hearth protection in front of it. Some fireplaces are too small or shallow. Many factory-built fireplaces are not approved for inserts. Gas inserts also need a gas supply. We connect a gas insert to an existing gas line, but we do not run or install new gas lines; if a new line is needed, a plumber or your gas utility handles that part. Permits may also apply in your town.

Living with an insert

An insert changes how you use the fireplace. A few things owners notice:

• Wood inserts burn best with dry wood and enough air. Long low burns build deposits in the liner, so the liner still needs cleaning on a regular schedule.
• Gas inserts are simpler day to day, but the glass, burner and venting still need service. See gas fireplace service.
• Pellet inserts need regular ash removal and cleaning of the burn pot and vent, and they depend on electricity to run.
• Many inserts have a blower that moves warm air into the room. It needs power and occasional cleaning.

What affects the scope

The insert type and size, liner length and diameter, chimney height and roof access, any repairs needed first, hearth extension needs and gas or electrical connections. For a gas insert, a new gas line, if one is needed, is separate work for a plumber or your gas utility.

The condition of the masonry chimney matters too. A liner protects the house from the exhaust, but a chimney with a failing crown or leaking flashing will still let water in and can damage the new installation. Those repairs are best done before the insert goes in.

Next step

Request an insert assessment. If you have a model in mind, include it. A team member will contact you to confirm a time.

Questions homeowners ask