Double glazing offers excellent insulation and energy efficiency, but it can lose effectiveness if the seals fail. Recognising a blown double-glazed window early helps you address the issue promptly and maintain your home’s comfort.

Understanding Blown Double Glazing

Blown double glazing occurs when the seal between the glass panes breaks. This failure allows moisture to enter the gap, reducing the window’s insulating properties. Identifying the signs helps you decide when to repair or replace the unit.

Look for Condensation Between the Panes

Persistent Fogging

Moisture trapped inside the glass unit causes fogging or condensation that won’t wipe away. Unlike exterior condensation, this issue remains between the panes and indicates a broken seal.

Water Droplets

You may notice visible water droplets forming inside the glass. This sign confirms moisture intrusion and signals a blown window.

Check for a Cloudy Appearance

Hazy Glass

Blown double glazing often looks cloudy or misty due to dirt or condensation trapped inside. This haziness reduces visibility and diminishes the window’s aesthetic appeal.

Dull or Dirty Look

Even after cleaning, the glass may appear dull. This issue occurs when debris or moisture accumulates between the panes, making the window less transparent.

Feel for Draughts Around the Frame

Cold Spots

Stand near the window and check for cold air. A blown seal may allow draughts to seep in, reducing energy efficiency and making the room feel colder.

Higher Energy Bills

Increased heating costs may indicate reduced insulation caused by blown double glazing. Pay attention to these subtle changes over time.

Inspect the Window for Structural Issues

Distorted Glass

A blown unit may show slight warping or bulging. The pressure changes inside the glass unit cause this distortion and suggest seal failure.

Broken Seal Lines

Look closely at the edges of the glass. Cracks or breaks in the sealant indicate a problem that needs addressing.

Test with Light Reflection

Uneven Reflections

Stand at an angle and check how light reflects on the glass surface. Uneven or distorted reflections may signal a blown seal or damaged pane.

Moisture Marks

Use a flashlight to examine the inside of the panes for streaks or marks. These indicate trapped moisture resulting from a broken seal.

What to Do If You Notice Blown Double Glazing

Once you confirm a blown seal, consider your options:

– Replace the Unit: A full replacement restores insulation and clears up fogging. Consult a professional to ensure proper installation.
– Repair the Seal: In some cases, resealing the unit may fix minor issues and delay the need for replacement.
– Upgrade to Energy-Efficient Glass: If replacing the window, consider upgrading to modern energy-efficient glass to improve insulation and reduce energy costs.

Conclusion

Blown double glazing affects insulation, visibility, and energy efficiency. By checking for condensation, cloudy glass, draughts, and other signs, you can identify the problem early and take appropriate action. Regular inspections and maintenance help keep your windows performing at their best.