- Energy Efficiency Requirements: For ENERGY STAR certification, product glazing shall have Emissivity and Solar Transmissions ratings certified by an approved third-party certification body at levels which meet or exceed the certification criteria described in the following table for a given climate zone.
ENERGY STAR Climate Zone Emissivity Solar TransmissionNorthern ≤ 0.22 > 0.55North-Central ≤ 0.22 AnySouth-Central ≤ 0.22 ≤ 0.55Southern ≤ 0.22 ≤ 0.55
- Air Leakage Requirements: For ENERGY STAR certification, products shall have Air Leakage ratings at levels which meet or exceed the certification criteria specified in the following table.
Product Air Leakage Rating Exterior Storm Window ≤ 1.5 cfm/ft2 Interior Storm Window ≤ 0.5 cfm/ft2
Definitions of Performance Metrics
- Emissivity: The relative ability of a surface to reflect or emit heat by radiation. Emissivity ranges from 0 to 1.
- Solar Transmittance (Tsol): The ratio of transmitted radiant flux in the solar spectrum (300 nm to 2500 nm) to incident radiant flux in the solar spectrum.
- Air Leakage: A measure of the rate of air passing through a material or assembly in the presence of an applied pressure difference, expressed in units of cfm/ft2.