For exterior & architectural animations, you need to use two engines that are designed for environments. The IR-Mapping is an approximation and will cause flickering for most scenes; I only use it for interior & studio product STILL shots. So, I recommend (1) Brute Force and (2) Light Cache.
This is all straight from my new Bongo Course which was launched on Friday at lynda.com Check out all of the details on this course in a prior post there at McNeel.