If you have noticed a hazy, foggy, or misty appearance between the panes of your double glazed windows, that is not condensation on the surface. It is moisture that has got inside the sealed unit, which means the seal has failed. Here is what causes it, what your options are, and what it costs to fix in Tauranga.
Why Do Double Glazed Windows Go Foggy?
A double glazed unit, also called an IGU or insulated glass unit, consists of two panes of glass with a sealed air or gas-filled cavity between them. The seal around the edge keeps moisture out and maintains the insulating properties of the unit.
Over time the seal degrades. Heat cycles, warming up during the day and cooling at night, cause the unit to expand and contract repeatedly. Eventually the seal fails and allows moisture from the air to enter the cavity. That moisture condenses on the inner surfaces of the glass and creates the foggy or hazy appearance you can see from outside.
Once the seal has failed the unit cannot be repaired, it needs to be replaced. There is no method to reseal a failed IGU or remove the moisture without replacing the glass unit entirely.
Can You Fix Foggy Double Glazing Without Replacing the Whole Window?
Yes, in most cases. The aluminium frame and the joinery do not need to be replaced. We remove the failed sealed unit from the existing frame and install a new IGU in its place. This is called a sealed unit replacement, and it is significantly cheaper than replacing the whole window.
The process works for most standard aluminium frames. Older frames or frames that have been damaged may need assessment before we can confirm replacement is possible.
How Long Do Double Glazed Sealed Units Last?
A quality sealed unit installed correctly should last 15 to 20 years. Seal failure before 10 years usually indicates an installation issue, a manufacturing defect, or damage to the frame that allowed moisture ingress.
If multiple units in your home are failing at the same time it often indicates they were all installed at the same time and are reaching the end of their lifespan together. This is common in homes built in the 1990s and 2000s in Tauranga, glass repairs.
Should You Repair or Replace All Windows at Once?
If one unit has failed it does not mean all of them are about to fail. We recommend replacing failed units individually as they fail unless the entire home has the same installation date and multiple units are showing signs of failure simultaneously.
Replacing all windows at once is a larger investment but avoids the ongoing disruption of individual replacements over several years. We can advise on the condition of your other units at the quote stage.
What About Upgrading to Better Glass at the Same Time?
When replacing a failed sealed unit you can upgrade the glass specification at the same time for a relatively small additional cost. Options include:
- Acoustic laminated glass, reduces outside noise significantly. Popular for homes near main roads in Tauranga, Mount Maunganui, and Papamoa.
- Low-E glass, a coating that reduces heat loss in winter and heat gain in summer. Improves energy efficiency beyond standard double glazing.
- Argon-filled units, the cavity is filled with argon gas instead of air for improved insulation performance.
We will advise on which upgrade is worth the cost for your specific situation.
What Does Double Glazing Repair Cost in Tauranga?
Sealed unit replacement is priced per unit based on the size and glass specification. As a general guide:
- Standard double glazed sealed unit replacement: from $250 to $500 per unit installed
- Acoustic or Low-E upgrade units: from $350 to $700 per unit installed
- Larger units (ranch sliders, floor to ceiling panels): priced individually
For most standard Tauranga homes, replacing a failed sealed unit is considerably cheaper than replacing the whole window and frame.
How Do You Know If It Is a Seal Failure or Just Surface Condensation?
Surface condensation, on the inside of your home, forms when warm moist air meets a cold glass surface. This is common in winter and usually clears when the room warms up or is ventilated.
Seal failure, the fog is between the two panes and does not clear regardless of temperature or ventilation.
A simple test: wipe the glass on both surfaces. If the fog clears it is surface condensation. If it remains it is between the panes and the seal has failed.
