Another design input: If there's lots of humidity inside the room you'd probably prefer negative pressure in the room. Reason: positive pressure can pressure

Another design input: If there's lots of humidity inside the room you'd probably prefer negative pressure in the room. Reason: positive pressure can pressure moist air through walls and ceilings and when it hits the cold air on the other side of the insulation it condenses in thr construction and causes rot (or corrosion).