Abstract: A ventilated transportable freight container is disclosed. The container is ventilated by natural convection through at least one lower side vent comprising a lower plenum chamber for distributing air into the container and restricting entry of moisture in the form of rain, sleet or snow into the container and at least one upper top vent, including a plenum chamber. The upper top vent or vents may be formed in the sidewall of the enclosure or in the roof of the enclosure depending upon the structure of the container and the particular application. The use of one or more upper top vents enhances circulation of air by natural convection. The invention also incorporates sidewall and endwall spacers extending from the sidewalls and endwalls into the enclosure to provide passageways for the circulation of air to ventilate the enclosure and a path for condensation drainage. In one embodiment of the invention, the transportable freight container of present invention comprises a rail freight car.