Girl At The Window

• Thermal transmittance (U-factor). Best values are around U-0.15 (equal to 0.8 W/m2/K).
• Solar heat gain coefficient (SHGC) (ratio of solar heat (infrared) passing through the glass to incident solar heat)
• Visible transmittance (VT) (ratio of transmitted visible light divided by incident visible light)
• Air Leakage (AL) (Measured in cubic foot per minute per linear foot of crack between sash and frame)