U-Factor measures how well a product can keep heat from escaping from the inside of a room. The lower the number, the better a product is at keeping heat in. Range: 0.20–1.20 | Look for: Low numbers
Solar Heat Gain Coefficient (SHGC) measures how well a product can resist unwanted heat gain, which is especially important during summer cooling season. The lower the number, the less you’ll spend on cooling. Range: 0–1 | Look for: Low numbers
Visible Transmittance (VT) measures how well a product is designed to effectively light your home with daylight, potentially saving you money on artificial lighting. The higher the number, the more natural light is let in. Range: 0–1 | Look for: High numbers
Air Leakage measures how much air will enter a room through a product. The lower the number, the fewer drafts you’ll experience. Range: 0.1-0.3 | Look for: Low numbers