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Specifications – Glass Performance Data Sheet

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Analysis data supplied by PPG Industries and Cardinal Glass for glass as used in Metropolitan High Performance Windows’ vinyl windows and doors and may not apply to products as produced by other manufacturers. Standard design conditions available upon request.

Glass Type Visible Light Transmittance Ultra Violet Blockage Relative Heat Gain BTU/HR-SQ FT Winter U’Value Winter U’Value w/Argon Shading Coefficient
CLR/CLR 81% 42% 189 0.49 0.47 0.87
CLR/GRAY 56% 69% 153 0.50 0.47 0.57
CLR/BRONZE 62% 67% 154 0.50 0.47 0.62
CLR/AZURELITE 70% 69% 113 0.49 0.47 0.53
CLR/LOE SQ 72% 84% 98 0.30 0.24 0.47
LOE SQ/GRAY 49% 92% 80 0.30 0.24 0.34
LOE SQ/BRONZE 55% 92% 80 0.30 0.24 0.37
CLR SINGLE GLAZE* 90% 27% 215 1.11 N/A 0.98


*Single glazed clear data reported for reference purposes only.
*All calculations performed using DOUBLE STRENGTH GLASS with ½ ” air space for a total insulated glass unit thickness of ¾”.

What Does This All Mean?

Relative Heat Gain – The total amount of heat gain through a glazing system at NFRC/ASHRAE specified summer conditions, incorporating the U-value and the Solar Heat Gain Coefficient. The conditions are 230 Btu/hr/ft², outdoor temperature of 89°F, indoor temperature of 75°F, and 7.5 mph wind.

Expressed in terms of Btu/hr/ft²

Visible Light % – In the visible spectrum (380 to 720 nanometers), the percentage of light that is transmitted through the glazing relative to the C.I.E. (International Commission on Illumination) standard observer.

UV% – Conventionally, it is considered that UV (Ultra Violet) energy accounts for the majority of fading. This fading potential can affect fabrics, paints, artwork and other materials. To compare like products, UV transmittance (as a percentage) is used to indicate fading potential.

U-Value – The heat flow rate through a given construction expressed in Btu/hr/ft²/°F. Values are normally given for NFRC/ASHRAE winter conditions of 0° outdoor temperature, 70° Btu/hr/ft² indoor temperature, 15 mph wind and no solar load. U – values on this table are expressed in terms of the glass alone and compared to other glazing options.