Natural light plays a huge role in home design, affecting energy efficiency, comfort, and aesthetics. When choosing new windows, one of the key performance ratings to consider is Visible Transmittance (VT).
In this guide, we’ll explain what VT means, how it affects your home, and how to choose the right level of visible transmittance for your windows.
What Is Visible Transmittance (VT)?
Visible Transmittance (VT) measures how much natural light passes through a window. The higher the VT rating, the more daylight enters your home.
How VT Is Measured
- Measured on a scale from 0 to 1 (or as a percentage from 0% to 100%).
- Higher VT (0.70+) means more natural light.
- Lower VT (0.30 – 0.50) means less light but better glare control.
Typical VT Ratings for Windows
| Window Type | VT Rating | Best For |
|---|---|---|
| Clear Double-Pane Glass | 0.60 – 0.80 | Maximizing daylight |
| Low-E Coated Glass | 0.40 – 0.70 | Balanced light & energy efficiency |
| Triple-Pane Low-E Glass | 0.30 – 0.50 | Glare control & insulation |
How VT Affects Your Home
1. More Natural Light & Daylight Control
- Higher VT means brighter rooms and less need for artificial lighting.
- Lower VT helps reduce glare in sunny areas.
2. Energy Efficiency
- Windows with a high VT let in more heat, which may increase cooling costs.
- Low-E coatings help control heat gain while maintaining good VT.
3. Interior Comfort & UV Protection
- High VT windows let in more light but can also cause fading in furniture & flooring.
- Low-E glass helps filter harmful UV rays while keeping daylight.
Choosing the Right VT for Your Home
The best VT depends on your home’s design, location, and how much daylight you prefer.
- For bright, open spaces: Choose VT 0.60+ to maximize daylight.
- For glare control & energy savings: Choose VT 0.40 – 0.55.
- For hot climates: Pair a lower VT (0.30 – 0.50) with Low-E coatings to block heat.
Upgrade to Energy-Efficient Windows
Not sure which windows provide the best balance of natural light and energy savings? Get a free quote today and find the perfect windows for your home.
Learn More About Window Performance
Check out these related guides: