This thread has me confused now
I saw in somewhere in the West on my travels, possibly up in Bannack, a building that had two separate doorways that led into stairwells for access to individual rooms on the second storey. I assumed it was on a/c of the very cold climate and prevented heat loss when the occupants of such rooms were coming and going. I'm thinking perhaps maybe that is your answer.
UpSideDownC
in New Zealand