U-value (Thermal Transmittance) is the rate of heat transfer through a structure. The U-value is an assigned value that gauges the resistance of the transfer of heat from the outside to the inside or the inside to the outside of the fenestration, the lower the U-value, the higher the resistance.
Sans 613
SANS 613 is the South African national standard for mechanical/structural performance criteria. The criteria include water tightness, deflection, structural strength, and air tightness.