Originally posted by pipo.p:

What is 0.5 meters high in game?

the walls tell you. a standard wall is 2M tall, the half walls are 1M, so 1/2 of a half wall.
I consider 3M to be a 'room' height, enough room for a portal that isnt blocked by the ceiling (usually). A viking can function in a 2M tall room, though, its just really tight.