Best Windows for Boise: Treasure Valley Recommendations

Boise and the Treasure Valley sit in IECC Climate Zone 5B—cold winters but relatively mild by Idaho standards. According to NOAA data, Boise averages about 5,833 heating degree days annually. Here's what that means for window selection.

Recommended Specifications

According to ENERGY STAR and U.S. Department of Energy guidance for Zone 5:

| Specification | Minimum | Recommended |
|---------------|---------|-------------|
| U-factor | ≤ 0.27 | ≤ 0.25 |
| SHGC | Any | 0.30-0.40 |
| Frame | Any | Vinyl or fiberglass |

Why These Numbers

U-factor ≤ 0.25: According to DOE, exceeding ENERGY STAR minimums by a small margin provides meaningfully better comfort during Boise's coldest days (which can still drop below 0°F).

SHGC 0.30-0.40: The Treasure Valley has hot summers with temperatures exceeding 100°F. Lower SHGC on west-facing windows helps manage afternoon heat gain. But don't go too low—passive solar gain still helps in winter.

Summer Considerations

Unlike Idaho Falls or Sun Valley, Boise has meaningful cooling loads. According to NOAA, Boise averages 30+ days above 90°F. Consider:

• Lower SHGC on west-facing windows
• Exterior shading (awnings, trees) where practical
• Don't sacrifice U-factor for SHGC management

Double vs. Triple Pane

For most Boise homes, according to DOE guidance:

• **Double-pane Low-E with argon** is the sweet spot
• **Triple-pane** provides additional comfort but longer payback
• Save triple-pane budget for problem areas (large north windows, comfort-critical rooms)

The Bottom Line

Boise's Zone 5B climate allows more flexibility than colder parts of Idaho. Quality double-pane Low-E windows meeting ENERGY STAR requirements serve most Treasure Valley homes well.

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