The 2012 IgCC will require the U-factor and SHGC for fenestration to be 10% lower than that of the 2012 IECC when the prescriptive energy compliance path is chosen.
The prescriptive path will be limited to buildings less than 25,000 sq. ft. in area.
Since the outcome based compliance path was also deleted from the IgCC, buildings greater than 25,000 sq. ft. in area will need to be designed using the performance based path of the 2012 IECC.