The purpose of this program was development of commercial production plans for a practical and cost effective energy conserving retrofit system for windows based on Sunteks prototype Superpane retrofit window. The original Superpane configuration consisted of a transparent insulation know as Heat Mirror to reduce radiative heat loss, a thermally sensitive optical shutter known as Cloud-gel to reduce summer heat gain, and a contained air space to reduce convection, all related to the prime window by an appropriate edge detail.