Why Is My House Cold?
Comprehensive heat loss diagnosis guide for New Zealand homes
Heat lost through uninsulated ceilings
Heat lost through walls & windows
Heat lost through floors & air leaks
Cold House Diagnostic Tool
Find Your Heat Loss Sources
Answer these questions to identify why your house is cold and get personalised solutions
1. When does your house feel coldest?
Common Causes of Cold Houses in NZ
Poor Ceiling Insulation
Up to 60% of heat loss occurs through uninsulated or poorly insulated ceilings.
Air Leaks & Drafts
Cold air infiltration through gaps around windows, doors, and penetrations.
Thermal Bridging
Heat conducting through structural elements like wall studs and concrete slabs.
Moisture & Humidity
High humidity makes the house feel colder and reduces heating efficiency.
Inadequate Heating
Undersized or inefficient heating systems for the home's size and heat loss.
Building Design
Poor orientation, high ceilings, or large windows without adequate insulation.
Heat Loss by Building Era
Pre-1950s Houses: Vintage Homes
Common Issues:
- • No ceiling insulation (0 R-value)
- • Single-glazed windows
- • Timber floors on piles (cold underfloor)
- • Large air gaps and drafts
- • High ceilings = more volume to heat
Priority Solutions:
- • Add ceiling insulation (R3.2-3.6)
- • Seal major air leaks
- • Install heavy curtains or blinds
- • Consider underfloor insulation
- • Upgrade heating system
1950s-1980s Houses: Post-War Homes
Common Issues:
- • Minimal ceiling insulation (R1.5 or less)
- • No wall insulation
- • Concrete slab floors (thermal bridging)
- • Aluminium window frames
- • Basic construction methods
Priority Solutions:
- • Upgrade ceiling insulation to R3.2+
- • Add wall insulation where possible
- • Install carpet/rugs over concrete
- • Upgrade to double glazing
- • Seal window and door frames
1980s-2000s Houses: Basic Insulation Era
Common Issues:
- • R1.5-2.0 ceiling insulation (inadequate)
- • Some wall insulation but with gaps
- • Thermal bridging through studs
- • Basic double glazing in later builds
- • Insufficient ventilation systems
Priority Solutions:
- • Add extra ceiling insulation to R3.2+
- • Improve wall insulation coverage
- • Install proper vapour barriers
- • Add mechanical ventilation
- • Upgrade heating efficiency
Post-2000s Houses: Modern Standards
Potential Issues:
- • Insulation settling over time
- • Poor installation quality in some builds
- • Air leakage around services
- • Inadequate heating for open plan designs
- • Thermal bridging in some constructions
Improvement Options:
- • Top-up ceiling insulation if settled
- • Seal remaining air leaks
- • Optimise heating system zoning
- • Consider continuous insulation upgrades
- • Add ventilation heat recovery
Regional Climate Factors
Northern NZ (Auckland/Northland)
- Challenge: High humidity makes it feel colder
- Solution: Dehumidification + R2.9 minimum ceiling insulation
- Priority: Moisture management critical
Central NI (Waikato/Bay of Plenty)
- Challenge: Temperature swings and frost
- Solution: R3.2+ ceiling insulation essential
- Priority: Good ceiling insulation prevents ice dams
Southern NZ (Canterbury/Otago)
- Challenge: Extreme winter cold and wind
- Solution: R3.6+ ceiling insulation + air sealing
- Priority: Maximum insulation levels needed
Quick Heat Loss Assessment
DIY Heat Loss Check
Visual Inspection
- 🔍 Ceiling Access: Check if insulation is visible, measure depth with ruler
- 🪟 Window Test: Hold hand near windows to feel drafts
- 🕯️ Candle Test: Move lit candle around door/window frames to detect air movement
- 🌡️ Temperature Mapping: Check temperature differences between rooms
Professional Assessment
- 📷 Thermal Imaging: Professional thermal camera assessment shows heat loss patterns
- 💨 Blower Door Test: Measures air leakage throughout the house
- 🏠 Building Assessment: Complete evaluation of thermal performance
- 📊 Energy Audit: Detailed analysis with improvement recommendations
Solution Priority Guide
🥇 Highest Impact Solutions (60-80% improvement)
Ceiling Insulation Upgrade
- • Cost: $1,800-3,500 (average home)
- • Payback: 3-7 years through energy savings
- • Impact: 40-60% reduction in heat loss
- • Eligible for government grants
Air Leakage Sealing
- • Cost: $500-1,500 (DIY or professional)
- • Payback: 1-3 years
- • Impact: 15-25% improvement
- • Often combined with insulation work
🥈 Medium Impact Solutions (20-40% improvement)
Window Upgrades
- • Double glazing: $800-1,200 per m²
- • Heavy curtains: $200-500 per window
- • Window film: $50-150 per window
- • Impact: 10-20% improvement
Wall Insulation
- • Retrofit: $25-45 per m²
- • External cladding upgrade
- • Cavity fill where possible
- • Impact: 15-30% improvement
🥉 Supporting Solutions (5-20% improvement)
Heating Upgrades
- • Heat pump: $3,000-6,000
- • Efficient wood burner: $2,000-5,000
- • Heating controls and zoning
- • Right-sizing for house thermal performance
Floor & Other
- • Underfloor insulation: $15-25 per m²
- • Ventilation improvements
- • Thermal mass additions
- • Solar gain optimisation
Frequently Asked Questions
Why is my house so cold even with heating on?
Poor insulation allows heat to escape faster than your heating system can replace it. Ceiling insulation is typically the biggest culprit - up to 60% of heat loss occurs through uninsulated ceilings. Air leaks around windows and doors also allow cold air to enter continuously.
How much difference does ceiling insulation make?
Upgrading from no insulation to R3.2 ceiling insulation can reduce heat loss by 40-60%. This typically results in 25-40% lower heating costs and significantly improved comfort. Many homeowners notice the difference within days of installation.
What's the most cost-effective way to warm up my cold house?
Ceiling insulation offers the best return on investment, typically paying for itself in 3-7 years through reduced heating costs. Combined with sealing air leaks, this addresses 60-80% of heat loss issues. Start with the ceiling, then address other areas based on your budget.
Can I get financial help to insulate my cold house?
Yes, the government's Warmer Kiwi Homes programme provides grants up to $1,300 for ceiling and underfloor insulation. Low-income households may qualify for up to $9,000 in funding. Many regional councils also offer additional rebates.
Why do older houses feel so much colder?
Houses built before 1980 typically have little to no insulation, single-glazed windows, and numerous air gaps. They were designed when energy was cheap and thermal performance wasn't prioritized. Modern insulation standards require R2.9-R3.6 ceiling insulation compared to R0-R1.5 in older homes.
Should I fix the insulation or upgrade my heating first?
Always improve insulation first. Installing efficient heating in a poorly insulated house is like trying to fill a bucket with holes in it. Once you reduce heat loss through better insulation, you may find you need less heating capacity, allowing you to choose a smaller, more efficient system.
Stop Living in a Cold House
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