Innovative curtain wall with solar preheating of ventilation air and integrated control system

There is a growing demand for curtain walls within the European Union, coming mainly from the commercial sector and especially targeted to office buildings. Despite recent efforts on heat loss mitigation (relying on additional glass panes, coatings or thermal breaks to framing elements) curtain walls remain a significant contributor to the energy consumption of such buildings. This paper presents the design and development of an energy-efficient alternative to conventional curtain wall systems, achieving equivalent transparency and aesthetics with greater comfort and reduced energy consumption. An integrated air cavity, sandwiched between glazing layers of thoroughly selected properties, harvests heat from both incident solar radiation and transmission losses recovered from the indoor environment. The system can supply the airflow required for ventilation with preheated fresh air, thereby reducing energy consumption in the heating season, and even delivering net gains in favourable conditions. Thereby the building envelope acquires an active role within the ventilation system, acting both as a solar collector and a heat recovery device. Whenever solar gains are not sought, a bypass element allows the natural ventilation of this air cavity, acting as a ventilated façade. An integrated control system with embedded electronics and actuators allows for a smart control of the system with no intervention required from the user.The authors wish to acknowledge the financial support received from the Basque Government through the HAZITEK programme (project ref. ZL-2016/00720, ZL-2017/00571), supporting experimental development and industrial research projects