Realizing optimal radiative cooling walls in building-energy nexus via asymmetric emissivity

With the gradually warming climate, the global cooling demand for buildings is rapidly increasing. Radiative cooling (RC) has been an attractive electricity-free approach to reducing the energy consumption of buildings. Current RC strategies focus on roofs; however, limited attention has been paid to vertical walls. Here, we report a zigzag-based structural design with asymmetric emissivity to realize optimal RC walls. Such asymmetry leads to a daily average temperature drop of 2.3°C compared to conventional walls coated with RC materials. When the ground is at ∼56°C, the temperature drop reaches 3.1°C, corresponding to a relative cooling power of 67 W m⁻² compared to the control wall. Moreover, the energy impact of this zigzag wall in diverse climate conditions is analyzed based on building-scale simulations. Current limitations and future improvement directions are also discussed. This zigzag RC wall provides a new passive solution to energy-efficient buildings.