Covered wagon of which the body is built with insulating walls, doors, floor and roof, by which the heat exchanges between the inside and outside of the body can be so limited that the overall coefficient of heat transfer (K coefficient), is such that the equipment is assignable to one or other of the following two categories: - I N = Normally insulated equipment - characterized by a K coefficient equal to or less than 0.7 W/m 2 degrees C - I R = Heavily insulated equipment - characterized by a K coefficient equal to or less than 0.4 W/m 2 degrees C