Open the Rhino example file:
The grey blocks represent building envelopes. They must be modelled as B-rep (Boundary Representation) geometry. To push these envelopes to the UrbanDaylight analysis stack press “1”. A window will pop up with more detailed settings [See "Builder"]. With “2“ blockage geometry can be pushed to the stack. Blockage geometry are also B-reps that directly touch facades of the buildings. All other shading geometry is pushed to the stack with “2”.