Energy Performance is reported as a group of values designated by the National Fenestration Ratings Council (NFRC) to provide meaningful, comparative data for windows, doors, and skylights. The NFRC has determined that these values represent the key energy performance factors when measured and reported in a standardized method.
These values are:
• Solar Heat Gain Coefficient (SHGC)
• Visible Light Transmittance (VLT)
• Condensation Resistance (CR)
• Air Leakage or Air Infiltration
All performance values are determined through product testing following industry standard specifications. Actual product performance will depend on the specific details of the application in which the product is installed. This includes how well the product was installed, the physical environment and conditions of the location as well as other factors.
The rate of heat or thermal transfer through the product is measured in BTU/h*ft2*°F. The lower the U-Value, the better the insulating value of the product.
Measures the fraction of Solar Energy transmitted and tells you how well the product blocks heat caused by sunlight. SHGC is measured on a scale of 0 to 1. The lower the SHGC, the less Solar Heat the product transmits.
Measures the amount of light the product lets through. VT is measured on a scale of 0 to 1. The higher the VT, the more light you see.
Measures how well the product resists water buildup. Condensation Resistance is scored on a scale from 0 to 100. The higher the number, the more resistant the product is to water buildup.
Measures the rate at which air passes through joints in the product. It is measured in cubic feet of air passing through one square foot of product area per minute. The lower the value, the less air leakage. Most industry standards and building codes require an AL of 0.3 cf•m/ft².