A coaxial ventilator exchanges atmosphere between parts of a building that are at differing heights. The coaxial ventilator includes an outer conduit that extends from an upper end thereof downward to a lower end thereof. The outer conduit surrounds an inner conduit that extends substantially the entire length of the outer conduit. Both the outer and inner conduits are open at their respective upper ends and lower ends. Temperatures of atmosphere both surrounding and within the outer conduit and the inner conduit induce an exchange of atmosphere between the coaxial ventilator and surrounding atmosphere.