Idaho Climate Zones: What They Mean for Your Windows

Not all of Idaho has the same climate—and that affects which windows you should choose. According to the International Energy Conservation Code (IECC), Idaho spans multiple climate zones with different heating demands.

Idaho's Climate Zones

According to IECC classifications:

| Zone | Idaho Regions | Heating Degree Days |
|------|---------------|---------------------|
| 5B | Boise, Nampa, Twin Falls, Pocatello | 5,000-6,000 |
| 6B | Idaho Falls, Rexburg, Sun Valley | 6,000-7,000 |
| 7 | High mountain areas | 7,000+ |

According to NOAA climate data, Idaho Falls averages 25% more heating degree days than Boise—meaning significantly more heating demand.

What This Means for Windows

According to ENERGY STAR, different zones have different minimum requirements, but more importantly, different optimal specifications:

Zone 5 (Treasure Valley, Twin Falls)

• Minimum: ENERGY STAR U-factor ≤ 0.27
• Recommended: U-factor ≤ 0.25
• Double-pane Low-E is typically adequate

Zone 6 (Idaho Falls, Sun Valley)

• Minimum: Same ENERGY STAR requirement
• Recommended: U-factor ≤ 0.22
• Consider triple-pane for best comfort

Zone 7 (Mountain Communities)

• Recommended: U-factor ≤ 0.20
• Triple-pane strongly recommended
• Consider higher SHGC for passive solar gain

The Bottom Line

A window perfect for Boise may underperform in Idaho Falls. According to the IECC, understanding your specific climate zone helps you choose windows that will actually meet your heating needs—not just minimum code requirements.

*For complete climate zone guidance, see: [Climate Zone Window Selection](/guides/climate-zone-window-selection-idaho)*