Thanks for the reply, not sure what you mean (and probably means I haven't explained myself)...

A room made of single faced planes (presumably like yours), single infinite light, with or without IBL. Daylight scene, light through windows. External (infinite) light leaks through the seams where the planes intersect. Your room must be open at the camera side judging from the shadows; an enclosed room with an infinite light and no other lights would not have a shadow pattern like yours.