Janus Gradient Porous Membranes with Switchable Radiative Cooling and Solar Heating for Building Thermal Management.

Area of Science:

• Materials Science
• Nanotechnology
• Building Physics

Background:

• Conventional building materials have fixed optical properties, limiting their ability to adapt to seasonal thermal management needs.
• Passive thermal management strategies require materials that can dynamically modulate spectral properties for efficient cooling and heating.

Purpose of the Study:

• To develop and demonstrate a novel Janus gradient porous membrane (JGPM) for switchable passive building thermal regulation.
• To enable adaptive cooling in summer and solar heating in winter through a simple flipping mechanism.

Main Methods:

• Fabrication of JGPMs using solvent template-assisted evaporation-induced phase separation (ST-EIPS) with carbon black modification.
• Characterization of hierarchical porosity (nano- to microscale) and spectral properties for tailored solar-thermal response.
• Testing of prototype architectural applications under simulated and real-world environmental conditions.

Main Results:

• The white surface achieved subambient cooling of 11.7 °C (96.06% solar reflectance, 94.69% emissivity).
• The flipped black surface achieved a 22.5 °C temperature rise (97.07% solar absorptance).
• Prototype testing confirmed seasonal adaptability with 5.7 °C cooling and 10.3 °C heating benefits.

Conclusions:

• JGPMs offer a transformative solution for adaptive building thermal management by enabling switchable radiative cooling and solar heating.
• The material's mechanical robustness and component adhesion support direct surface application.
• Demonstrated reliable performance across diverse conditions highlights JGPM potential for energy-efficient buildings.