A grain bin aeration system has inlet ducting in communication with the hollow interior of the storage bin adjacent a perimeter of the storage bin and exhaust ducting in communication with the hollow interior of the storage bin at a central location within the storage bin. A first portion of the inlet ducting is directed to the top end of the bin so that aeration flow therethrough is directed downwardly through the material in the storage bin to the exhaust ducting. A second portion of the inlet ducting is directed to the bottom end of the bin so that aeration flow therethrough is directed upwardly through the material in the storage bin to the exhaust ducting.