By Wellington Glass & Mirror
If you’re considering double glazing in Wellington, one of the most common questions is how long it will actually last. It’s an important question because double glazing is a long-term investment in comfort, energy efficiency, and the performance of your home. In Wellington’s windy, coastal climate, the lifespan of double glazing depends on quality specification, expert installation, and ongoing maintenance.
How long does double glazing actually last?
It’s a fair question. Upgrading your windows is an investment in your property, including energy efficiency, comfort and long-term performance. You want to know it’s going to stand the test of time, especially in Wellington’s windy, coastal conditions.
Here’s what you need to know.
The Average Lifespan of Double Glazing
Modern, high-quality double glazing typically lasts 20 to 30+ years
In many cases, it can last even longer when properly manufactured, installed, and maintained.
However, longevity depends on several key factors:
- Correct glass specification for your joinery, window size and wind load
- Manufacturing quality of both your joinery and double-glazing units
- Window frame type and condition
- Installation workmanship
- Weather conditions
- Ongoing maintenance
At Wellington Glass & Mirror, we focus on getting these details right from the start.
If you’re replacing old double-glazing units, you may also find this article helpful:
👉 Replacing Failed or Old Double Glazing in Wellington
Why Quality Matters in Wellington’s Climate
Wellington is known for:
- Strong winds and very high wind loads, which put pressure on glass and seals
- Salt-laden coastal air
- Rapid weather changes
- High UV and moisture levels
- Lots of older houses which can move over time
These conditions can accelerate wear on glazing systems.
As a Certified RetroGlaze® Partner, we only install high-performance RetroGlaze® window and door systems, engineered to perform and last under New Zealand conditions. We ensure the quality and compliance of the glass and glazing system specified for your home, all manufactured components, and our installation services are designed and built to handle the environmental conditions common in Wellington and specific to your home.
What Causes Double Glazing to Fail?
Failure typically occurs when the seal between the panes of glass and the spacer bar breaks. Once the seal is compromised, insulating gas escapes, moisture can enter the cavity, and performance is lost.
This can be caused by:
Low-quality joinery or double-glazing units
Poorly designed or manufactured joinery or double-glazing units have a reduced lifespan. This can occur with products that are not specifically designed, tested or rigorously quality controlled to NZ Standards and conditions. Not all joinery and double-glazing units available in NZ are equal. For more information, see https://www.wganz.org.nz/media-release/
Poor specification or fit
Incorrect specification of glass or materials for your specific joinery type and wind zone may result in exposure of the double-glazing unit seals to water or harmful UV light, resulting in failure. The strength and integrity of the external seal between units and window frames is also crucial for resistance to wind and rain.
Incompatible materials
In timber joinery, incompatibility of sealants used in the manufacture and installation of double-glazing units, and between sealants, timber treatment and paint systems used, can significantly affect lifespan.
Poor Installation
Incorrect installation can result in water ingress or stress the glass unit, leading to damage of frames and/or premature seal failure.
Frame Deterioration
In retrofit scenarios, the condition of existing timber or aluminium frames supporting the glass and of the frames connecting the joinery to the house also plays a key role in long-term durability. Water ingress and/or blocked drainage can result in damage to both double-glazing units and rot or deterioration in the surrounding frames or walls.
Awareness of these factors is why expert assessment, engineer-designed systems, quality manufacturer and expert installation all matter as much or more than the selection of the glass or joinery itself.
Retrofit vs Inserts vs Full Frame Replacement: Does It Affect Longevity?
At Wellington Glass & Mirror, we specialise in tailored solutions, including:
- Timber retrofit double glazing
- Aluminium retrofit double glazing
- Timber replacement sashes
- Aluminium inserts
- Aluminium full frame replacement joinery
When retrofit double glazing is done correctly, it can last just as long as replacement systems. The key difference is not lifespan, but suitability for your home’s existing frames, surrounds and performance goals.
If you’re weighing up your options, this comparison guide is helpful:
👉 Aluminium Insert vs Timber Retrofit in Wellington
Our approach is simple: recommend the right solution for the property, not a one-size-fits-all option.
Signs Your Double Glazing May Need Attention
You may need and expert assessment if you notice:
- Condensation trapped between panes
- Visible moisture or fogging
- Drafts around frames
- Reduced thermal performance
- Water accumulating on the inside of windows or doors
If you’re unsure, our team can assess whether the issue is the sealed unit, the frame, or simply ventilation.
How to Maximise the Lifespan of Your Double Glazing
You can extend performance by:
- Cleaning glass and frames regularly
- Checking drainage holes and channels in aluminium joinery remain clear
- Properly maintaining and painting timber frames
- Ensuring adequate ventilation in wet areas
- Addressing minor issues or evidence of deterioration early
Well-maintained double glazing can comfortably exceed 25 years of service.
Is Double Glazing Worth It Long-Term?
In Wellington, absolutely!
High-performance double glazing can:
- Significantly reduce heat loss and improve insulation of your home
- Reduce condensation
- Reduce over-heating, UV damage and furniture fading
- Reduce noise entering and leaving through windows and doors
- Enhance everyday comfort
- Increase property value
Modern units can reduce heat loss by up to 83% depending on the specification chosen.
It’s not just about lifespan. It’s about long-term performance and comfort.
Frequently Asked Questions About Double Glazing Costs in Wellington
Quality double glazing typically lasts 20 to 30 years or more. In Wellington’s coastal climate, quality joinery, high-performance, hermetically sealed units, correct specification and installation is critical for longevity.
Properly installed retrofit double glazing can last just as long as new replacement systems, provided the existing frames are in good condition.
Yes. Seal failure can cause fogging and condensation between panes and reduce thermal performance. This is often referred to as a “blown” unit. Quality specification, manufacturing and professional installation significantly reduce this risk.
Look for internal condensation between panes, persistent fogging, or noticeable drops in thermal performance.
Salt air can impact lower-quality materials over time. High-performance systems designed for New Zealand conditions are built to withstand coastal exposure.
No, “blown” or failed units cannot be repaired, they must be replaced. In many cases, the sealed unit can be replaced without replacing the entire window frame, making repairs cost-effective. However. In some cases repair or replacement of the surrounding frame is also needed.
Thinking About Upgrading Your Windows?
Whether you’re upgrading a character villa in Mount Victoria, a 1960s home in Lower Hutt, or a modern build on the Kāpiti Coast, we can help you find and install the best option for your home.