the building envelope, which mainly consists of transparent and opaque components. For transparent components (e.g., window), the STRMMs should have high transparency of visible light (0.38-0.76 µm) under both hot and cold ambient conditions to guarantee natural lighting. Nearinfrared (NIR) light (0.77-2.5 µm), which accounts for 52% of solar heat, [9] should be reflected in summer for cooling purpose but be transmitted into room in winter to induce solar heat gains. For opaque components (e.g., wall), the STRMMs should have high reflectance of both visible and NIR lights in summer but low reflectance of both lights in winter. Meanwhile, as both transparent and opaque components continuously emit thermal radiation into the outdoor ambient, the STRMMs should have low infrared thermal emissivity in winter to suppress radiative heat loss but high infrared thermal emissivity in summer to accelerate radiative heat dissipation. Figure 1b shows the ideal optical properties of STRMMs applied on transparent and opaque components in both heating and cooling modes. Existing reviews mainly focused on the daytime radiative cooling materials with fixed solar reflectance and thermal emissivity, [10][11][12] which only helps reduce building cooling loads in summer but inevitably increases building heating loads in winter, leading to limited building energy savings. Recently, owing to the rapid development of material science, the STRMMs have been widely explored, which can dynamically modulate the optical properties under external triggers (e.g., thermo and electrical) to accommodate the heating/cooling needs of building in different seasons, showing improved building energy-saving potentials. [13][14][15][16][17] Although there are reviews reporting the materials with modulating optical properties, [15,18] they merely focused on either solar or thermal radiation modulation, which provide limited or even negative building energy savings, which may mislead the researchers to design low energy-efficient materials in practice. For instance, the thermochromic (TC) window can achieve low solar transmittance in hot season but high solar transmittance in cold season. [13,19] Nonetheless, it maintains high thermal emissivity (above 90%) in both seasons. This would accelerate heat loss of building in cold season, and result in limited energy savings. The vanadium dioxide (VO 2 )-based Fabry-Perot (FP) resonator can achieve low thermal emissivity in cold season but high thermal emissivity in hot season, while it maintains constant solar absorptance (25%) in both seasons. This would induce much more solar heating than the conventional cooling materials with smaller solar absorptance (10%), resulting in Regulation of solar and thermal radiation of building envelope shows huge energy-saving potentials. Existing reviews mainly focus on the materials with fixed solar and thermal optical properties. Although there are reviews reporting the materials with modulated optical properties (e.g., radiative cooling materials with modulating thermal emi...
