Solar Ray Tracing only tracks a ray until it reaches the first opaque wall, after this there is no more ray tracing done and with this no “real” reflection. In the boundary condition panels for walls absorptivity and (for semi-transparent walls) transmissivity has to be defined. 1 minus these values is the portion which is handled as reflected. The reflected solar flux will summed up and then distributed to the energy sources of all walls (with participation on solar ray tracing activated). This is also called as internally scattered energy. The fraction of the scattered energy which is distributed to the walls can be changed by the TUI command /define/models/radiation/solar-parameters/scattering-fraction The default value is 1 so all reflected energy is distributed. A value of 0 means all reflected energy is just taken out of the calculation.