From GridLAB-D Wiki
glazing_shgc – The glazing heat gain coefficient (SHGC) is the fraction of incident solar radiation admitted through a window.
Synopsis
object house { glazing_shgc value %; }
Remarks
Glazing_shgc is expressed as a value between 0 and 100%, 0 being the least solar heat transmission, and 100% being the most.
Default
See table for glazing_shgc by window_frame in Default House.