Stop Window Condensation with Double Glazing: Complete NZ Guide
Struggling with dripping windows, mould growth, and water damage from condensation? Double glazing eliminates 90% of window condensation by keeping your window panes warmer than the dew point. This guide explains why condensation happens, how double glazing solves it, and what results to expect.
Is Condensation Damaging Your Home?
- ❌ Windows drip with water every morning
- ❌ Mould growing on window frames and sills
- ❌ Curtains damp and musty-smelling
- ❌ Water pooling on windowsills
- ❌ Paint peeling around windows
- ❌ Timber frames rotting from moisture
- ❌ Black mould on walls near windows
- ❌ Constant wiping needed each morning
- ❌ Health issues (allergies, asthma)
- ❌ Difficulty heating home (heat escapes)
If this sounds familiar, double glazing can solve your condensation problem permanently.
The Solution: Double Glazing
What You Can Expect:
90-95%
Reduction in condensation
No More Drips
Dry windows, even in winter
Mould Prevention
Eliminates mould growth triggers
Why Does Condensation Happen?
Understanding the science helps you appreciate why double glazing works so well:
Warm Air Holds Moisture
When you cook, shower, breathe, or dry clothes indoors, moisture enters the air. Warm air can hold lots of water vapor—up to 17g per cubic meter at 20°C.
Cold Surfaces Can't Hold Moisture
When warm, moist air touches a cold surface (like single-glazed windows in winter), it cools rapidly. Cold air can't hold as much moisture, so the water vapor condenses into liquid droplets.
Windows Are the Coldest Spot
Single-glazed windows are the coldest surface in your home (often 5-10°C colder than room temperature). This makes them a magnet for condensation—all the moisture in your home ends up on your windows.
The Dew Point: This is the temperature at which air can no longer hold moisture and condensation forms. Single-glazed windows are often below the dew point in winter, while double glazing stays above it.
How Double Glazing Stops Condensation
Single Glazing ❌
Outside temp: 5°C (cold winter day)
Inside temp: 20°C (heated room)
Window surface temp: 8-10°C
→ Below dew point (12°C)
→ Heavy condensation forms
Result: Dripping windows, pooling water, mould growth
Double Glazing ✓
Outside temp: 5°C (same cold day)
Inside temp: 20°C (same heated room)
Window surface temp: 16-18°C
→ Above dew point (12°C)
→ Little to no condensation
Result: Dry windows, no mould, healthy home
Why Double Glazing Keeps Windows Warmer
- ✓ Insulating air gap: 12-16mm of trapped air between panes acts as a thermal barrier, dramatically reducing heat transfer
- ✓ Inner pane stays warm: The inner glass pane stays much closer to room temperature (16-18°C vs 8-10°C for single glazing)
- ✓ Outer pane takes the cold: The outer pane gets cold, but it's isolated from your room by the air gap
- ✓ Above dew point: Because the inner surface stays warm, it remains above the dew point and condensation can't form
Condensation Reduction: Real Results
What Different Homes Experience
🏠 Average Family Home (2-4 people)
Before: Heavy condensation every morning. Daily wiping required. Mould on bedroom window frames.
After: Minimal to zero condensation, even on coldest mornings. Windows stay dry. No mould growth.
Typical reduction: 90-95%
🏘️ Rental/Older Home (Poor Ventilation)
Before: Extreme condensation. Water pooling on sills. Black mould everywhere. Curtains permanently damp.
After: Massive improvement (85-90% reduction). Some minor condensation remains if ventilation poor, but easily manageable.
Note: Add ventilation (bathroom/kitchen extractor fans) for best results
🏡 New/Modern Home (Good Insulation & Ventilation)
Before: Some morning condensation on single-glazed windows despite good insulation elsewhere.
After: Zero condensation, even in coldest weather. Windows perfectly dry year-round.
Typical reduction: 95-100%
🌊 Coastal Home (High Humidity Areas)
Before: Year-round condensation issues. Worse in winter but present even in summer due to high ambient moisture.
After: Major improvement in winter (90% reduction). Some light condensation may occur on most humid days but dramatically better overall.
Recommendation: Combine with dehumidifier in extreme humidity
Additional Benefits of Eliminating Condensation
🦠 Healthier Home
- ✓ Eliminates mould and mildew growth
- ✓ Reduces respiratory issues (asthma, allergies)
- ✓ Prevents dust mite proliferation
- ✓ Improves indoor air quality
- ✓ Better for children and elderly
🏠 Protects Your Home
- ✓ Prevents timber frame rot
- ✓ Stops paint peeling around windows
- ✓ Protects curtains and blinds from moisture damage
- ✓ Reduces maintenance costs
- ✓ Increases property value
💰 Energy Savings
- ✓ Reduces heating costs by 30-40%
- ✓ Home stays warmer with less heating
- ✓ Eliminates cold drafts from windows
- ✓ More even temperature throughout house
- ✓ Pays for itself in 7-12 years
🛋️ More Comfortable
- ✓ No morning window wiping routine
- ✓ Can close curtains without dampness
- ✓ Warmer rooms, less cold spots
- ✓ Quieter home (60-80% noise reduction bonus)
- ✓ Overall better quality of life
Will I Still Get Any Condensation?
Honest Answer: Most homes see 90-95% reduction, but you may still get light condensation in these situations:
- ✓ Extreme temperature differences: If it's -5°C outside and 22°C inside with high humidity, some condensation can still form
- ✓ Poor ventilation: If you don't ventilate properly (no extractor fans, windows never opened), excess humidity has nowhere to go
- ✓ High indoor humidity: Drying clothes indoors, no rangehood, multiple people showering can create extreme moisture
- ✓ Very cold regions: Queenstown, Central Otago winters can be so cold that even double glazing gets minor condensation
However, any remaining condensation will be minor compared to the dripping, pooling water you experience with single glazing.
Maximizing Condensation Prevention
Double glazing is the foundation, but these tips ensure zero condensation:
Proper Ventilation
Use extractor fans in kitchen/bathroom when cooking or showering. Open windows for 10-15 minutes daily to refresh air. Consider HRV/DVS ventilation system for whole-home solution.
Control Humidity
Aim for 40-60% relative humidity (use a hygrometer to measure). Use dehumidifier if consistently above 70%. Dry clothes outside or in dryer vented outside.
Adequate Heating
Keep home at 18-20°C minimum. Warm air holds more moisture and prevents it condensing on surfaces. Double glazing makes heating more effective and affordable.
Moisture Management
Close kitchen/bathroom doors when cooking/showering. Use lids on pots. Vent tumble dryers outside. Avoid portable gas heaters (they create lots of moisture).
Customer Success Stories
"We had black mould all around our bedroom windows from condensation. Every morning I'd wipe litres of water off the windows. Since installing double glazing, our windows are bone dry even on the coldest mornings. The mould is gone and we can finally breathe easily!"
Rachel & Tom, Wellington
uPVC double glazing, whole house
"Our rental was freezing with constant condensation. The landlord finally agreed to double glaz the place and it's been life-changing. No more wiping windows, our daughter's asthma has improved dramatically, and we're using 30% less power to heat the home."
Sarah, Christchurch
Standard double glazing, bedroom windows
"Living near the coast in Auckland, we had humidity issues year-round. Our curtains were always damp and musty. Double glazing solved it completely - windows stay dry even on the most humid days. Best home improvement we've ever done."
Mike & Emma, Auckland
Aluminium double glazing, coastal home
"We were wiping water off our windows twice a day. The window frames were starting to rot from the constant moisture. Three months after double glazing installation, we haven't wiped a single window. It's honestly like magic!"
James, Dunedin
uPVC retrofit double glazing
Cost vs. Ongoing Damage
Cost of NOT Fixing Condensation
- • Mould remediation: $500-2,000
- • Replacing rotted window frames: $1,500-3,000 per window
- • Repainting damaged areas: $500-1,500
- • Replacing damaged curtains: $200-800
- • Medical costs (allergies/asthma): Ongoing
- • Higher heating bills: $500-800/year extra
Ongoing damage costs add up fast!
Investment in Double Glazing
- • Small window: $500-800
- • Medium window: $800-1,200
- • Large window: $1,200-2,000
- • 3-bedroom house (12 windows): $10,000-18,000
Benefits:
- ✓ Eliminates condensation (90-95%)
- ✓ Prevents mould & damage
- ✓ Saves $500-800/year on heating
- ✓ Increases property value
- ✓ 20-30 year lifespan
Pays for itself in 7-12 years through energy savings alone!
→ See detailed regional pricing and cost calculator
Condensation & Double Glazing FAQs
Will double glazing completely eliminate condensation?
Double glazing eliminates 90-95% of condensation in most homes. You may still get light condensation in extreme conditions (very cold, high humidity, poor ventilation), but it will be minor compared to single glazing.
How long after installation before condensation stops?
Immediately! The first morning after installation, you'll notice dry windows. The effect is instant because the inner glass pane stays warm from day one.
I have double glazing but still get condensation. Why?
Possible causes: (1) Condensation between panes (seal failure - needs repair), (2) Extreme indoor humidity (need better ventilation), (3) Very old double glazing with poor performance (consider upgrading), (4) Poor installation with air leaks.
Can I just ventilate more instead of double glazing?
Ventilation helps but doesn't solve the root cause - cold windows. You'd need to ventilate so much that your home becomes freezing cold. Double glazing addresses the problem at the source by keeping windows warm.
Will double glazing fix my mould problem?
If the mould is caused by window condensation, yes. Double glazing removes the moisture source. However, you may need to clean existing mould first. For mould from other sources (leaky roof, damp walls), additional solutions needed.
Is retrofit double glazing as good as full replacement for condensation?
Yes! Both retrofit and full replacement provide the same thermal performance and condensation prevention. Retrofit is cheaper and works with existing frames, making it a great option for most homes.
Do I need special glass for condensation prevention?
No, standard double glazing is excellent for condensation. You don't need special coatings or gas fills - the basic air gap between panes is what keeps the inner pane warm and prevents condensation.
My landlord won't pay for double glazing. What can I do?
From July 2024, NZ's Healthy Homes Standards may require landlords to address condensation/mould issues. Present evidence of the problem and request double glazing. If refused, consider using a portable dehumidifier and improving ventilation as temporary measures.
Stop Condensation Today
Get free quotes from condensation prevention specialists. Say goodbye to dripping windows, mould, and moisture damage forever.