Housing
Housing is defined as the part of the settlement, the housing facilities, where the people have their personal space, be they apartments or the equivalent of actual houses. It is different from lodging facilities where the occupants are expected to be transient.
On Mars, housing needs to provide a breathable atmosphere, protection from radiation and a comfortable environment. It may have external windows, but these need to be designed in a way that prevents excessive radiation exposure. Artificial lighting is likely to be standard.
Housing may come from Earth in the form of modules that can be assembled together with other elements to create a settlement, or built on site with in-situ resources.
Requirements
Minimum living space for housing depends partly on cultural elements, but varies from a minimum of about 10 m2 per person to a comfortable 40m2 per person in most of Europe and 60-70m2 per person in the US and Canada.[1] With a height of 2,3m, this corresponds to volumes of 23, 92, 140 and 160m3.
NASA has explored the minimum volumes required for long term stays in space[2]. The minimum volume was set at 25m3 per person for a maximum of 912 days. This includes a personal space of 5m3 per astronaut. Space can be used much more effectively in the microgravity environment of a space mission, and these values would be unacceptable for Martian housing. The value of 40m2 might be a fair compromise for settlers, 30 or less might apply to visitors, or to an experimental base rather than a settlement.
