Harnessing the potential of radiative cooling for the built environment: a new comprehensive protocol for materials' characterization

The pursuit of novel materials for radiative cooling (RC) holds immense promise in addressing building energy saving and urban overheating. RC capitalizes on the principle of dissipating heat energy into space, specifically through the atmospheric window between 8-13 μm, to achieve passive cooling of surfaces. However, the absence of a standardized and reliable methodology for characterizing RC materials has introduced inconsistencies in research findings, impeding collective advancements in the field. To address this issue, a dedicated experimental protocol is here introduced, as a unifying benchmark for the characterization of RC materials. This procedure aims to provide comprehensive, consistent, and precise data regarding crucial properties of RC cooling materials, including thermal stability, spectral radiative behavior, and thermal performance under both controlled and realistic boundary conditions. To demonstrate the effectiveness of our proposed methodology, we designed and implemented a comparative study involving an aluminum-based and a Vikuiti-based sample incorporating a silica-derived polymer as an emissive layer. Notably, our findings reveal that the Vikuiti prototype outperforms the aluminum counterpart, primarily attributable to its superior solar reflectance and thermal emittance characteristics. This research not only advances our understanding of RC materials but also offers a crucial step toward uniform characterization methods that can catalyze further research and scaling up of radiative cooling technologies.