Jee is an eco-sustainable and energy-efficient window and façade system to be applied in dwellings or office buildings. It´s an object to be manufactured in series and designed to have a large range of applications both in refurbish as in new constructions. Mixing passive low-tech solutions with others more sophisticated and high-tech, Jee takes advantage from solar radiation to improve significantly: the heat exchanges, daylighting and ventilation that occur between indoor and outdoor environments. Increasing energy efficiency over 40% reduces tons of CO2 emissions from spaces operation during a 20years life cycle. The lab tests performed on a prototype during a seasons cycle confirmed it. JEE is patented (Invention Patent Nº.10379), design registered (EU UtilityModel) and ready to produce.