This type of multiple doorway (the literal translation of the Greek term, polythyron) is a regular feature of cult buildings and other sets of ceremonial rooms. They are closed by sets of double double doors that swing on pivot stones set into the threshold and fit into recesses cut into the jambs on either side. Because of this, they are sometimes known as pier-and-door partitions.
Since he found them in areas of the palace that he deemed residential, Evans thought they were used for climate control—light and ventilation. The angle of the sun and the direction of the wind are important considerations when it comes to comfort in Crete, but windows fitted with shutters would have served just as well. In any case, there is little to indicate that the rooms in question were residential.
Very often, polythyra are associated with lustral basins, which are now generally believed to be ritual installations, and probably served some role in cult activity. Doorways would suggest the movement of groups of people taking part in that activity with the doors themselves being used shut the room in darkness or open it up to the light.