How to Install a Wood-Burning Fireplace Insert

Pay attention to two measurements when choosing and installing a fireplace insert. The first measurement is the insert's dimensions. It needs to fit inside of your existing fireplace. 

Measure the fireplace opening's height, width, and depth using a tape measure. If you have one, use a laser measuring tool. The tool takes accurate measurements with the help of a laser beam and is much easier to manipulate than old-school, flexible metal measuring tape.

The second measurement concerns the heat output of the fireplace insert. An insert's heating capability is measured using British Thermal Units (BTUs). The more BTUs, the more heat the insert can produce. Bigger rooms require an insert with a higher BTU.

Measure the room's dimensions to determine how many BTUs you need. You'll need to find the room's area, in square feet. For a rectangular room, the math is pretty straightforward. Measure the room's width and length, then multiply the two. 

You'll need to flash back to high school geometry to find the area of irregularly shaped rooms, such as a circular or triangular space. The formula to find an area of a circle is 3.14 times the square of the room's radius (half the diameter). To find the area of a triangle, multiply the length by the width, then divide by two. 

Once you have the room's area, multiply by 20 to get the BTU measurement.

Spread a plastic drop cloth over the area in front of the fireplace to prevent scratches or other damage during the installation. Also, don your safety goggles and gloves to protect yourself.

If you’re converting your fireplace from gas to wood-burning, you’ll need to cap off the gas line. Find the gas pipe that supplies gas to your home from the utility company. Look for the valve connected to the pipe. When open, the valve's handle is parallel with the pipe.

Turn the valve's handle 90 degrees, so that it is perpendicular to the pipe, to shut off the gas. After you've turned off the gas, unscrew the gas lines in your fireplace with pipe wrenches.

To cap the gas line into the fireplace, coat the threads with the pipe dope, then screw a fitting size cap on top.

Once you've done that, you can turn the gas back on.

You need to remove the damper to pass the flue liner between the chimney and insert. You may be able to remove the damper by lifting it out through the guides by the flapper. If that doesn't work, you'll have to cut the damper free.

Use the grinder to cut through the flapper and lift the damper free. Keep your safety goggles and gloves on while using the grinder.

Scared of heights? It may be time to call in a chimney repair professional. Otherwise, recruit a friend to spot you and follow all ladder safety precautions so you can climb up to the top of the chimney to install the flue liner.

Once you're on the roof, remove the chimney cap and thread the liner into the chimney.

Have a person on the ground slide the insert into your fireplace opening. Connect the flue line to the adapter on top of the insert. Use screws and a screwdriver to secure it in place. 

From the roof, trim away the excess liner from the top of the chimney with tin snips and discard it. Use high-temperature silicone on top of the flue tile, then attach the chimney cap, pressing down for a secure seal.

Attach the surround panels to the sides of the insert with screws. Clean up your drop cloth and any debris or dust, then step back and admire your handiwork.