When choosing new windows, you’ll come across U-Factor and Solar Heat Gain Coefficient (SHGC). These two ratings play a major role in energy efficiency, insulation, and comfort inside your home.
In this guide, we’ll break down what U-Factor and SHGC mean, how they affect your home, and how to choose the right ratings for your climate.
What Is U-Factor?
U-Factor (or U-Value) measures how well a window prevents heat from escaping. The lower the U-Factor, the better the insulation.
How U-Factor Is Measured
- Rated between 0.20 to 1.20 – lower numbers mean better insulation.
- Applies to entire window, including glass, frame, and spacers.
- Lower U-Factor windows keep homes warmer in winter and cooler in summer.
Best U-Factor Ratings by Climate
| Climate | Recommended U-Factor |
|---|---|
| Cold Climates (High Insulation Needed) | 0.20 – 0.30 |
| Moderate Climates (Balanced Performance) | 0.30 – 0.40 |
| Warm Climates (Less Heat Retention Needed) | 0.40 – 0.50 |
What Is Solar Heat Gain Coefficient (SHGC)?
SHGC measures how much solar heat passes through a window. Lower SHGC means less heat enters, keeping your home cooler.
How SHGC Is Measured
- Ranges from 0 to 1 – lower values block more solar heat.
- Measured on a scale where 0.25 blocks more heat than 0.60.
- Higher SHGC windows let in more heat, useful for cold climates.
Best SHGC Ratings by Climate
| Climate | Recommended SHGC |
|---|---|
| Hot Climates (Keep Heat Out) | 0.20 – 0.35 |
| Moderate Climates (Balanced Performance) | 0.35 – 0.50 |
| Cold Climates (Passive Solar Heating) | 0.50 – 0.65 |
How U-Factor and SHGC Work Together
Windows with the right U-Factor and SHGC will maximize comfort and energy savings. Here’s how:
- Cold Climates: Choose low U-Factor (0.20 – 0.30) and high SHGC (0.50+) to let in winter sun.
- Hot Climates: Select low SHGC (0.20 – 0.35) and moderate U-Factor (0.30 – 0.40) to block heat.
- Mixed Climates: Go for a balanced U-Factor (0.30 – 0.40) and moderate SHGC (0.35 – 0.50).
Choosing Windows with the Right U-Factor & SHGC
Here are some key things to consider:
- Energy Star Ratings: Look for Energy Star-certified windows, which meet the best U-Factor and SHGC recommendations for your region.
- Low-E Glass: Low-E coatings help control heat transfer for better efficiency.
- Multi-Pane Windows: Gas-filled double or triple-pane windows improve insulation.
Get the Right Windows for Your Home
Not sure which U-Factor and SHGC ratings are best for your home, we can help? You can also get a free quote for energy-efficient windows today!
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