FWIW Perry VI table 12-5 and CRC's Handbook of Chemistry and Physics give daily solar radiation data over the year at various latitudes. If SHGC is what you want, there are a large number of sites that may be helpful, for example:
"Principles of Heating Ventilating and Air Conditioning" , Ronald Howell et al, A Textbook with design data based on the 1997 ASHRAE Handbook- fundamentals, 1998 ASHREA
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Also, for individual cities anyhwere on the planet, 5-10 years or hourly data is available on CD rom from NOAA. Excellent for computerized simulation of a process that is dependent on changin ambient conditions.