Ambient-adaptive multiple infrared-waveband radiation regulation of phase-change window for all-season building energy savings

Window accounts for more than 40% of building thermal loads. Phase change material (PCM)-based window has been proved to be effective to reduce building cooling and heating loads via latent heat store and release, respectively. However, the overall performance of the window is still limited due to the neglection of regulation of near-infrared (NIR) and mid-infrared (MIR) thermal radiation. To this end, a PCM- vanadium dioxide (VO 2 )-Indium Tin Oxide (ITO) composite window is proposed that integrates latent heat storage with multiple infrared-waveband radiation regulation by integrating VO 2 and ITO films for coordinated management of NIR and MIR radiation. In summer, the incident NIR radiation is reflected by the VO 2 film while the outdoor MIR radiation is suppressed into room by the ITO film. In winter, the incident NIR radiation is allowed to transmit into room while the indoor MIR radiation is blocked by the ITO film. The optical and thermal properties of the VO 2 and ITO coatings, as well as the phase-transition temperature and thickness of the PCM layer, were optimized, and the comprehensive optical performance of the composite window was characterized. Outdoor experiments show that the proposed window can increase and decrease the indoor temperature by 0.71 °C and 7.40 °C respectively in comparison with conventional PCM-based window. Building simulations demonstrate the proposed window can achieve up to 32.9% annual energy savings in diverse China climate regions. This study paves new way to develop advanced PCM-based window for improving the building energy efficiency. • A full-IR composite phase-change window (FIWCPCW) with VO₂, ITO and PCM is proposed for all-season building energy savings. • The optimized FIWCPCW achieves a near-infrared transmittance modulation of 11.0% and a low mid-infrared emissivity of 0.18. • Outdoor tests yield indoor changes of +0.71 °C (heating) and −7.40 °C (cooling) vs. a standard PCM window. • Simulations indicate 7.1–32.9% annual energy consumption across representative climatic regions. • FIWCPCW couples adaptive latent heat storage and multi-band IR regulation to enhance building thermal management.