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

## TL;DR

A new durable thermochromic coating is developed to help buildings save energy by adjusting solar heat gain across seasons.

## Contribution

A durable thermochromic coating based on an organogel-HA composite is introduced, offering improved optical modulation and real-world durability.

## Key findings

- The coating achieves a maximum absorptance modulation of 0.35 and 0.25 when applied on cement with a reflective underlayer.
- The material withstands UV exposure and thermal cycling without degradation.
- Simulations suggest up to 3% annual HVAC energy savings in diverse climates.

## Abstract

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.