Abstract: An insulated enclosure apparatus for use with an exhaust fan such as an attic fan which includes an upper frame through which air can exhaust and a lower frame for receiving air passing thereinto. The outer portion of the frame includes an upper frame and the lower frame that are each formed as two-piece units. Vertically extending panels extending therebetween to house the fan. A pivot axle is attached to the undersurface of each of the two doors for facilitating automatic opening and closing responsive to whether the fan is operating. Limit pins are included to restricted the distance of movement of the doors when opened. Gaskets can be attached along the door edges for sealing thereof to the upper frame.