Enhancing Urban Thermal Environment and Energy Sustainability With Temperature-Adaptive Radiative Roofs

Urban overheating threatens public health and energy sustainability. Traditional radiative cooling strategies, such as super cool materials with high albedo and high emissivity, produce undesired cooling during cold seasons and increase space heating demand — a phenomenon known as the heating energy penalty. A novel temperature-adaptive emissivity (TAE) roof coating, which shifts from a low emissivity under cold conditions to a high emissivity under hot conditions, has the potential to mitigate winter heating energy penalty.

In this study, we evaluate the impact of TAE roofs with and without high albedo on surface climate and building energy demand using a global climate model. Results show that TAE roofs provide effective winter warming, increasing urban temperature by an average of 0.16 °C and up to 0.54 °C (99th percentile), but have minimal effects on summer temperatures (mean change +0.05°C). Roofs with both TAE and high albedo maintains effective summer cooling benefits without exacerbating winter heating demand, especially in mid-latitude cities. Air temperature sensitivity to emissivity shows positive linear relationships with local apparent net longwave radiation, whereas its sensitivity to albedo has negative linear relationships with incoming solar radiation. Leveraging these relationships, we propose a simple parameterization framework to predict air temperature response to various roof emissivity and albedo changes, enabling a first-order assessment of climate responses to different roofing materials. Our findings highlight the significance of tailoring heat mitigation strategies specific to local climate.