A rigid-walled, block-shaped box is internally provided with a compartment arranged adjacent to a vertical wall of the box and having a first chamber with a first window open to the inside of the container and a second window open to the outside, and a second chamber with a third window open to the inside of the container and a fourth window open to the outside. The windows are each provided with a shutter. A mass of phase change material is housed within the compartment between said first chamber and second chamber, for absorbing heat from the air flowing from one chamber to the other chamber when said first window and third window are open and said second window and fourth window are closed, and releasing heat to the air flowing from one chamber to the other chamber when said first window and third window are closed and said second window and fourth window are open.