A story about bats and architecture

The resources of the earth are low, there were wars, nature is crazy, acid rain, catastrophes. The last remaining population of the earth is collected in one big university complex. In that gathering of people, everything seems to be normal (besides the fact that the end of the world happens), they are one (really) big family, there are no conflicts or hate. They don't have much time left on the earth. They have to move to another planet. It's an older earth which was left impossible to survive on. They have no other choice than moving there, because their chances to survive are higher on that planet. Dan and Phil are in the middle of all this, living through the catastrophes as a couple.
(Maybe inspired by "The 100" and "Interstellar")