National Fenestration Rating Council

Window Performance Guide
for Human Thermal Comfort


This glass guide covers four important areas of window performance, providing comparative
performance information and selection criteria for the following critical areas of performance:

Winter insulating performance
WINTER: ENERGY
EFFICIENCY AND
COMFORT
summer solar control
SUMMER: PROTECTION FROM SEARING
SOLAR HEAT
Sound Control
ALLOWING YOU
TO SEE
THE WORLD
ultra violet protection
EXTENDING THE LIFE AND
BEAUTY OF YOUR HOME'S
FURNISHINGS
Glass Temperature Recommended U-factors

U Factor map U Factor chart

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