Glass

How to Reseal a Leaking Double-Glazed Window

Posted on by mala mogodu
how to reseal a leaking double-glazed window – Get Glass
22
Jun

If you’ve noticed condensation, drafts, or water leaks around your windows, your double-glazed unit (IGU) may have a compromised seal. Fortunately, not all failures require a full replacement. This guide explains how to reseal a leaking double-glazed window, restore energy-efficient windows, and prevent long-term damage.

Common Signs of a Leaking Double-Glazed Window

  • Moisture or fogging between the panes
  • Water pooling at the sill or frame edges
  • Peeling paint or damp spots near the window
  • A noticeable draft, especially in winter
  • Whistling sounds during windy weather

Why Window Seals Fail

  • Aging of the perimeter sealant
  • Frame movement or thermal expansion
  • Poor original installation
  • UV damage breaking down silicone or rubber seals
  • Accidental puncture of the IGU edge

🛑 Once the inner seal is broken (moisture between panes), the IGU cannot be fully resealed—but the outer seal can be repaired to stop air and water ingress.

Step-by-Step: How to Reseal a Leaking Double-Glazed Window

✅ 1. Identify the Leak Source

Before resealing, determine where the water or air is entering:

  • Inspect the outside perimeter sealant
  • Check glazing beads, frame joints, and drain holes
  • Use a smoke pencil or incense stick to detect air leaks

📌 Leaks can occur at the glass-to-frame seal or at frame joints.

✅ 2. Clean the Area Thoroughly

  • Wipe down the window frame with mild detergent and water
  • Remove any old, cracked sealant using a utility knife or scraper
  • Ensure the surface is dry and free of dust or oils

💡 Dry thoroughly—sealant won’t bond to a damp surface.

✅ 3. Choose the Right Sealant

Use a neutral-cure silicone suitable for glass and uPVC/aluminium:

  • UV-resistant
  • Flexible and durable
  • Paintable if needed (optional)

Avoid cheap acrylic or acidic silicone, as these degrade quickly and may corrode aluminium.

✅ 4. Apply New Sealant to the Perimeter

  • Use a caulking gun to apply a smooth bead around the glass-to-frame joint
  • Tool the bead with a wet finger or sealant tool for a clean finish
  • Work in sections and smooth as you go—don’t wait for skinning

📌 For visible internal gaps, repeat the process from the inside for complete sealing.

✅ 5. Clear or Unblock Drainage Holes

Most window frames include weep holes to let water escape. Ensure they’re not blocked by:

  • Dirt
  • Paint
  • Old sealant

Use a thin wire or air blower to clear them.

✅ 6. Let the Sealant Cure

  • Allow at least 24 hours for full curing
  • Avoid washing windows or exposing to heavy rain during this time
  • Inspect after a day or two for any missed gaps

What This Repair Can and Cannot Fix

Issue Resealing Will Help?
Water entering from frame gaps ✅ Yes
Drafts around window edges ✅ Yes
Moisture inside double glazing ❌ No – needs new IGU
Structural frame damage ❌ No – replace frame

Bonus Tip: Add Window Insulation Film

If you can’t replace the failed IGU right away, applying a window insulation film on the inside can reduce heat loss and block some moisture.

When to Replace the IGU Instead

  • If the internal seal fails, allowing fog or moisture between panes
  • If the glass has cracks, chips, or temperature-related damage
  • If resealing doesn’t stop drafts or water ingress

Final Thought

Knowing how to reseal a leaking double-glazed window gives you the power to fix drafts and stop external leaks without immediate replacement. If fogging persists, however, it may be time to invest in a new IGU for lasting performance.

mala mogodu