Abstract: A retrofittable insulation system for solar rooms having glass bays supported by sills along the bottom and separated by vertically extending glazing bars. The system includes extruded, plastic double channel tracks secured to the inside of the glazing bars and extending substantially the full length thereof. An insulating shade sheet is carried by a roller supported on brackets mounted at the tops of adjacent glazing bars. The shade sheet has corded edges captured within the channels of the tracks and a batten is secured to its lower edge. Spring motors are mounted on the sill adjacent the bottom of each track, and cables connect the spring motors to the ends of the batten. The shade is operated by an actuator connected to the shade roller, which acts against the spring motors. In a preferred embodiment, the spring motors exert a pull force on the shade that varies in accordance with the force required to retract the shade which is a function of the relative position of the shade in the tracks.