Impact of Pavement Material Properties on Radiant Heat Exchanges with the Built Environment

There is a need for developing innovative pavement solutions for urban heat mitigation. This work presents the development of a model and a subsequent parametric study determining the impact of the material properties of pavements (thermal conductivity, heat capacity, solar absorptivity, infrared emissivity) over the surface temperatures of the ground and the boundary temperatures experienced by nearby buildings and people. The model explicitly considers dynamic heat storage effects, wind-dependent convective exchanges with the ambient, and the impact of solar and long-wave radiation exchanges. The parametric study compares the performance of a reference asphalt pavement to modifications (20% reduction) over each of its key material properties. Results indicate that the most relevant parameter is the solar absorptivity, followed by the emissivity. Changes in thermal conductivity or heat capacity have very limited effect. An interesting outcome is that reflective pavements with low solar absorption result in lower surface temperatures in the pavement, yet increased peak temperatures in neighbouring vertical surfaces (+2.5 °C) due to solar reflection and infrared radiative exchanges. In contrast, low-emissivity ground surfaces seem to achieve an opposite effect, increasing heat storage in the ground while reducing peak temperatures of nearby vertical surfaces (-1.2 °C).