The study aims to understand the thermal performance of a double skin envelope system in a test cell by configuring a module that has thermal stability with little indoor temperature variations. A rooftop observation deck and laboratory was installed at the "J" Building of the Postgraduate Unit, National Autonomous University of Mexico campus, UNAM (19°18'33.59" N, 99°11'5.73" W). This platform was designed to test materials and construction systems under the Mexico City microclimate, which consists of two full-scale testing modules. Each cubic module measures 3m x 3m x 3m. All of its facades have several layers of insulation. Indoor and outdoor parameters such as thermal, lighting, acoustic and air quality were measured during the experiment. The study aimed to achieve indoor thermal stability, benchmarked to be close to zero during the 24-hour thermal gradient. Findings showed that during warmer months, between May 19 and June 21, 2016, the envelope played an important role in decreasing the indoor air temperature by 7°C. The diurnal thermal gradient was 3.87°C.