Evolving buildings, isn't that when buildings change what they produce as you advance to different chapters? Anyway, thanks for the info.
Just to clarify, when someone mentions an "evolving building," they are referring to a building that requires evolution artifacts. There are not many: Coldfire Phoenix, Valentine Float, Gingerbread Mansion, Mermaids Paradise, Stonehenge, Polar Bear, Panda Bear, Brown Bear, Fire Phoenix, Storm Phoenix, Aureate Phoenix.
All other event buildings that produce a variety of goodies do so by "upgrading." That is changing a building from the chapter it is at (usually the chapter you were in when you won it), to one higher. This may or may not change what stuff if delivers, since those happen at levels specific to each building.
The evolving buildings are unique in that you can do both. You can evolve it more, or upgrade it's chapter level. With most of the evolving buildings, increasing the chapter (upgrading) does very little of use. Evolving is what will improve it the most, though the artifacts are extremely difficult to come by.