How to repair a broken seal on a double-seal window

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How to repair a broken seal on a double-seal window
Fix the seal on a double-seal window to ensure proper insulation. (window image by Marek Kosmal from

A double-seal window has a unique design that has certain advantages over traditional windows. It features a single frame that contains two sheets of glass side by side, rather than one. The separation between these panels is a vacuumed space that provides better insulation and reduces street noise and condensation. To maintain this type of efficiency, the seal on the frame must be airtight to prevent drafts, moisture and other outdoor elements from entering the room. Thus, repairing a broken seal is important.

Skill level:

Things you need

  • Silicone caulk
  • Utility knife
  • Wire
  • Rag
  • Vacuum
  • Caulking gun
  • Craft stick

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  1. 1

    Cut the damaged seal from the joint in the window frame, using a utility knife. Allow the majority to fall freely until the seams of the unit are exposed.

  2. 2

    Pry the remainder of the damaged seal with a putty knife for leverage if necessary. Use needle-nose pliers to peel especially thick or aged sealant.

  3. 3

    Wipe the exposed joints with a damp cloth to remove all visible residue. Vacuum any loose dirt or debris to ensure that no air is trapped underneath the new seal.

  4. 4

    Cut the tip on a tube of silicone caulk with a utility knife, leaving an opening approximately 1/4 inch wide. Insert a wire into the nozzle to puncture the foil seal, then load the tube into a caulking gun.

  5. 5

    Align the tip of the caulking gun with the joint between the exterior trim and sash of the frame. Apply steady pressure on the trigger and draw the tip along the length of it to fill the seam.

  6. 6

    Glide a craft stick over the application to firmly set the sealant. Use the same procedure if the damaged seal is between the glass panel and the window sill. Allow the silicone caulk to cure overnight.

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