All Climate Zones
Zone 3
Warm Climate Windows
Window selection guide for IECC Climate Zone 3: Warm climates including Las Vegas, Phoenix, Atlanta, and southern US regions.
Energy Code Requirement
U-0.40
U-Factor Maximum
Solar Heat Gain
SHGC ≤0.25 (REQUIRED for cooling efficiency)
SHGC Requirement
Heating Degree Days
2,000-3,500 annually
Annual Average
Climate Zone Zone 3 Characteristics
Temperature & Climate
- Climate Type
- Warm (Hot-Dry and Warm-Humid)
- Average Summer
- 90-105°F (32-41°C)
- Average Winter
- 40-60°F (4-16°C)
- Cooling Degree Days
- 2,500-4,500 annually
Energy Priorities
- Primary Concern
- Cooling costs dominate (60-70% of energy bill)
- Secondary Concern
- Moderate heating needs in winter
Specific Challenges for Warm Climates
- ▸Extreme summer heat requires aggressive solar control
- ▸Desert UV exposure (hot-dry) degrades seals faster
- ▸Temperature swings (50-60°F daily) stress window seals
- ▸Dust infiltration through aging seals (hot-dry climates)
- ▸Occasional freezing temps require some insulation
- ▸West-facing windows especially vulnerable to afternoon heat
Energy Code Requirements
- Energy Code
- IECC 2018/2021 Climate Zone 3
- Air Leakage Maximum
- ≤0.3 cfm/ft²
- Additional Notes
- Balance needed: SHGC ≤0.25 for cooling, U-0.40 adequate for minimal heating. Low-E3 coating standard.
Recommended Window Configurations
Standard Solar Control
Budget- Pane Count
- Double-pane
- Low-E Coating
- Low-E3 (solar control)
- Gas Fill
- Argon fill
- Frame Material
- Vinyl
- U-Factor
- U-0.32 to U-0.38
- SHGC
- SHGC 0.22 to 0.25
- Cost Range
- $450-$700 per window
- Payback Period
- 5-7 years
Advanced Solar Control
Premium- Pane Count
- Double-pane with spectrally selective coating
- Low-E Coating
- Low-E3 or Low-E4
- Gas Fill
- Argon fill
- Frame Material
- Vinyl or fiberglass
- U-Factor
- U-0.25 to U-0.30
- SHGC
- SHGC 0.18 to 0.22
- Cost Range
- $600-$950 per window
- Payback Period
- 6-9 years
Common Window Problems in Warm Climates
- Extreme solar heat gain requiring SHGC ≤0.25
- UV exposure degrading seals (15-18 year lifespan vs 20+ in cooler climates)
- Thermal stress cracks from rapid temperature changes
- Dust infiltration through aging seals (desert regions)
- Balancing solar control with adequate winter insulation
- West and south-facing windows bearing brunt of heat
Energy Cost Analysis
Annual Heating
$400-$800
Annual Cooling
$1,800-$3,200
Potential Savings
$450-$750/year with SHGC ≤0.22
Utility Rate
$0.11-$0.14/kWh
Recommended Window Products
Andersen
400 Series with SmartSun
SHGC 0.21, U-0.28, VLT 0.40
Marvin
Essential with LoĒ³-366
SHGC 0.23, U-0.29, Desert climate tested
Pella
250 Series with AdvancedLow-E
SHGC 0.24, U-0.30, Heat-resistant vinyl
Note: Product availability and specifications may vary. Always verify current specs with manufacturers and local dealers.