All-Season Thermochromic Organogel Polymers for Passive and Sustainable Building Efficiency

Regulating solar heat gain is crucial for reducing heating, ventilation, and air conditioning (HVAC) energy consumption in buildings and promoting sustainable responses to climate change. Current thermochromic materials suffer from poor durability and limited optical modulation. Here, the study presents a durable thermochromic coating based on an organogel-higher alkane (HA) composite. The reversible phase change of HA within the organogel induces light reflection, scattering, and diffraction, while carbon black particles enhance the absorptance modulation, achieving a maximum change of 0.35. For practical application on cement, where a highly reflective layer is applied beneath, the absorptance modulation can reach 0.25, exceeding reported values for other thermochromic systems that could be applied to the roof or wall. The material withstands prolonged UV exposure and repeated thermal cycling without degradation, making it suitable for real-world applications. Simulations incorporating a reflective underlayer demonstrate potential annual HVAC energy savings of up to 3% across diverse climate zones. This work introduces a robust, scalable, and season-adaptive thermochromic coating for sustainable building energy management.