The Housing Block is located next to the Medical Block. The crew would have slept here, which is the reason why there are no other bedrooms, besides one just outside, which would have been used for checking up on both blocks. It is one of two rooms impossible to enter. It says the formation change has to proceed in order to unlock the door. After the formation change takes place, you can't get past the giant fans. When you are in 0-G, you can get to the room, however, now the Lobby room used to get there is locked in order to maintain energy.