How to Replace a Window Seal

A failed window seal causes drafts, condensation between panes, and energy loss. Replacing the seal restores the window's performance and prevents further damage. Here's how to do it.

Types of Window Seals

"Window seal" can refer to several different things — it's important to identify which one has failed:

• IGU seal (insulated glass unit): The hermetic seal between the two panes of a double-pane window — cannot be DIY repaired; requires IGU replacement
• Glazing compound seal: The putty around the glass in a single-pane window — DIY replaceable
• Frame-to-wall caulk seal: The caulk between the window frame and the exterior wall — DIY replaceable
• Weatherstripping seal: The flexible seal between the sash and the frame — DIY replaceable

Replacing Glazing Compound (Single-Pane Windows)

1. Soften old glazing with a heat gun or hair dryer
2. Scrape out all old compound with a putty knife
3. Clean the rabbet thoroughly and let dry
4. Apply new glazing compound, pressing firmly into the corner between glass and frame
5. Smooth at a 45-degree angle with a wet putty knife
6. Let cure 7 days, then prime and paint

• DAP '33' Window Glazing White 32oz — professional-grade glazing compound; apply, smooth, cure, then paint for a weathertight seal

Replacing Frame-to-Wall Caulk Seal

1. Remove all old caulk with a caulk removal tool or utility knife
2. Clean the joint with rubbing alcohol and let dry completely
3. Apply painter's tape on both sides of the joint for clean lines
4. Apply a continuous bead of silicone caulk with no gaps
5. Smooth with a wet finger or caulk tool
6. Remove tape while caulk is still wet
7. Let cure per manufacturer instructions before exposing to rain

• GE Advanced Silicone Caulk Window & Door Clear — 100% waterproof, freeze and sun proof; the right product for exterior window frame sealing
• Bates Caulking Gun 10:1 No Drip — smooth, controlled bead application
• Caulking Tool 5-in-1 Silicone Removal Kit — remove old caulk cleanly before applying new

Replacing Weatherstripping Seal

1. Remove old weatherstripping by peeling or unscrewing
2. Clean the surface with rubbing alcohol
3. Measure and cut new weatherstripping to length
4. Peel backing and press firmly onto the door stop or sash channel
5. Test the window — it should close with slight resistance

• Weather Stripping Brush Pile Self-Adhesive 16.5ft — designed for sliding windows; pile brush seals irregular gaps
• Foam Weather Stripping Seal Tape 16ft (1/2" x 1/4") — self-adhesive foam for window stops and frame edges

For Failed IGU Seals (Double-Pane Fogging)

If the seal between the two panes of a double-pane window has failed (indicated by fogging between the panes), the entire IGU must be replaced by a glazier. This is not a DIY repair.