A Better Future, UndergroundG 25

A Better Future, Underground G25:
Upgrade 20 Rooms to Level 3

All rooms in the vault, with the exception of the elevator, can be upgraded to level 3. Each upgrade costs more caps than the last but improves the efficiency of that room by a pretty good amount. This achievement will unlock naturally as you play, but you can just build, upgrade, and destroy the same room over and over if you have the caps. Destroying a room refunds a small portion of the caps spent on the room, but it’s not much compared to the actual cost of building and upgrading. When 20 rooms have been upgraded to level 3, this achievement will unlock.