How to Close an Unused Chimney


Fireplaces are not as energy-efficient as many believe them to be. A fireplace can actually lose 10 percent more heat than it gives off. In addition to the chimney, a fireplace also requires care and regular maintenance to keep it working properly. If you've decided to stop using a fireplace in your home, you need to close the chimney. That will prevent heated (and cooled air) from escaping. It will also stop the outside air from coming in.

Things You'll Need

  • Ladder
  • Screwdriver
  • Measuring tape
  • Leather gloves
  • Sheet metal
  • Tin snips
  • Silicone caulking
  • Rigid foam insulation
  • Utility knife
  • Set the ladder up and climb on the roof to access the chimney. Use a screwdriver to loosen the screws on the chimney cap, if there is one. Lift the cap up and off, and set it aside. Measure the length and width of the chimney top.

  • Put on leather gloves to protect your hands from the sharp edges of the metal. Mark out the measurements of the chimney on a piece of sheet metal. Cut the piece out with a pair of tin snips.

  • Run a generous bead of silicone caulking around the top of the chimney. Place the sheet metal cut-out on the chimney and line it up with the edges. Press it down into place. Replace the chimney cap, if applicable.

  • Back inside the house, reach inside the fireplace and close the damper. Ensure that it's completely shut. Measure the opening in the chimney, in the top of the fireplace, right below the damper. Measure the length and width.

  • Mark out the measurements on a piece of rigid foam insulation. Cut the piece out with a sharp utility knife.

  • Place the insulation up into the chimney so it's wedged tightly into place. Run a bead of silicone caulking around where the insulation meets the chimney wall to ensure it's sealed completely.

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