What is U-factor, SHGC, and VT - Phoenix Green Homes

The U-factor of a window is its rate of heat loss,. The U-value is the reciprocal of the R-Value.  The lower the U-factor, the greater a window''s resistance to heat flow and the better its insulating value.  Essentially U-factor deals with the heat gain/loss of the actual window itself.

The Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat from sunlight. The SHGC is the fraction of the heat from the sun that enters through a window. SHGC is expressed as a number between 0 and 1. The lower a window''s SHGC, the less solar heat it transmits.  SHGC deals with how much heat gain comes through the glass of the window.

VT refers to visible light transmittance, or how much light gets through a window.  The higher the number, the greater the amount of light that comes through the window.

These three items can be found on a window's NFRC label. The National Fenestration Rating Council (NFRC) is a nonprofit, public/private organization created by the window, door, and skylight industry. It is composed of manufacturers, suppliers, builders, architects and designers, specifiers, code officials, utilities, and government agencies.