Energy-Efficient Window Replacement in Seattle, WA
Your complete guide to Washington energy codes, climate zone requirements, and window installation
Quick Facts: Seattle Window Replacement
Average Costs
- • Full installation: $450-1,150 per window
- • Double-pane: $380-750
- • Typical time: 2-3 weeks (rain delays common)
Energy Requirements
- • Climate zone: IECC Zone 4C (Marine)
- • U-factor: U-0.30 or lower for residential windows
- • 70+ NFRC-certified installers
Seattle's Marine West Coast Climate & Energy Needs
Summer Average
75°F (24°C)
Winter Average
45°F (7°C)
Heating Days
4,800
Cooling Days
200
Climate Zone: IECC IECC Zone 4C (Marine)
Climate Challenges for Windows
- ▸Constant moisture and rain exposure
- ▸High humidity causes condensation issues
- ▸Mold and mildew growth around frames
- ▸Limited sunlight extends installation times
- ▸Moderate heating needs, minimal cooling
- ▸Corrosion of metal frames from moisture
Washington Energy Code Requirements
Energy Code
Washington State Energy Code (WSEC) - among strictest in US
U-Factor Requirement
Windows must meet U-0.30 or lower for residential windows maximum. Lower is better for insulation.
Solar Heat Gain (SHGC)
No specific SHGC (cooling not a concern) to reduce cooling costs.
Permits
Washington requires building permits for window replacement. Installer should handle permits and inspections.
Frequently Asked Questions
How much does window replacement cost in Seattle?
Full installation: $450-1,150 per window per window. Double-pane glass: $380-750. Pricing depends on size, type, and energy ratings required by IECC Zone 4C (Marine).
What are common window problems in Seattle?
- Condensation and moisture between panes
- Mold growth on window frames and sills
- Water infiltration through aging seals
- Rot in wood window frames
Should I choose double-pane or triple-pane?
Double-pane Low-E typically sufficient for Seattle (4800 heating days). Triple-pane optional for north-facing windows.