I tried to see I/O reference manual but could not find it.

How come? Do you mean that you are not sure which to refer to from many variables in Surface Output Variables/Reports and Window Output Variables?

• Surface Inside Face Convection Heat Gain Rate
• Surface Inside Face Net Surface Thermal Radiation Heat Gain Rate
• Surface Window Transmitted Solar Radiation Rate
• Surface Window Inside Face Glazing Zone Convection Heat Gain Rate
• Surface Window Inside Face Glazing Net Infrared Heat Transfer Rate

In order to output the last two variables above, you need to select DisplayAdvancedReportVariables in Output:Diagnostics.