Abstract
Background
By the end of 2050, it is expected that 68% of the population will live in urban areas. A higher density of people living in cities generates an increased urban heat island. Radiative cooling (RC) materials are proposed as a key strategy to mitigate global warming and urban heating. The Horizon 2020 project MIRACLE aims at developing a new RC material based on conventional concrete.
This paper presents a framework developed for comparing both the cradle-to-gate environmental impact and cooling potential of the newly developed photonic meta-concrete (or any other new RC material) with existing RC materials. The framework is applied to various RC materials using the generic Ecoinvent v3.6 database. The impact assessment method is in line with the Belgian life cycle assessment method for buildings and covers the 15 environmental impact categories of the EN15804:A2. The cooling performance is assessed by implementing the material spectral emissivity into a thermal model for Brussels and Madrid.
Results
Collecting sufficient data to model the state-of-the-art RC materials is challenging, requiring numerous data points on materials, production, and performance, leading to many assumptions due to a lack of data. The study showed that the sputtering process contributes over 75% to the environmental impact of several materials, while materials which do not use this process, have significantly lower impacts. The assessment of the cooling potential showed that convection heat gains make it difficult to create an all-year round cooling material. The comparison with a conventional building material, a concrete roof tile, hence shows great potential for these RC materials as heating gains during summer are significantly reduced. Analysing cooling performance alongside environmental impact, the study identified two RC materials as the most preferred in both Brussels and Madrid, considering their lower environmental impact and superior performance.
Conclusions
A standardised way to asses and benchmark RC materials based on their cradle-to-gate environmental impact and cooling performance was lacking. For the first time, a comparison for RC materials considering these characteristics is presented. This comparison identified the most competitive RC materials, which will serve as benchmarks for the newly developed photonic meta-concrete.