How to Build a Draft Blocker for a Fireplace

Fireplaces are desired by many homeowners for both their decorative appearance and their heat. However, when there is no fire in it, warm interior air flows up the chimney and out of the house, thus causing energy loss. Closed dampers help prevent some of the leaks, but they are not airtight.

Seal unused fireplaces to prevent drafts.

The solution is to install a draft blocker which prevents any air from getting into the fireplace when it is not in use.

  1. Remove the fireplace grate and any other items in front of the fireplace to give yourself plenty of room to work.

  2. Measure the length and the width of the fireplace opening as accurately as possible. Take each measurement twice to ensure accuracy. Once you have the measurements, add 1/4 inch to both the length and the width. This extra measurement is required to keep the draft blocker in place.

  3. Lay a piece of foam insulation board on a work surface. Place a piece of plywood under the board to protect the underlying surface from damage.

  4. Draw the measurement of the fireplace opening onto the foam insulation board using the tape measure and a pencil. If needed, use a straightedge to create straight lines.

  5. Cut along each of the pencil lines using a utility knife and bearing down on the underlying plywood.

  6. Paint one side of the foam insulation board with any type of craft paint or cover it with wallpaper to blend it into the surrounding decor.

  7. Insert the draft blocker into the opening of the fireplace, pushing it in gently until it fits snugly.

  8. Tip

    When you are ready to light a fire, simply pull the draft blocker out by inserting a thin blade along the edge, if needed, to grasp the corner.