Milieu- en klimaatimpact van stralingskoelingsbeton Evaluatie van de materiaalgebonden milieu-impact, vermindering van het operationeel energieverbruik, mitigatie van het stedelijk hitte-eilandeffect en stralingsforcering

The Earth's climate is changing rapidly. In this context, buildings play a dual role: they contribute to climate change through emissions and also suffer its consequences. A key effect is the urban heat island (UHI), which increases energy demand for cooling, degrades ecosystems, and raises heat-related mortality. In response, mechanical cooling grows, driving up electricity use and emissions. This highlights the need for passive cooling strategies, improving both indoor comfort and urban temperatures. The H2020 MIRACLE project addresses this by developing a passive daytime radiative cooling concrete (PMC). Alongside its development, an environmental and climatic impact assessment is essential to understand its potential benefits and drawbacks, which is the focus of this dissertation. To benchmark new PMC, firstly the environmental impact and cooling performance of ten existing radiative cooling materials is assessed from cradle-to-gate. Impacts varied widely due to complex manufacturing processes, especially sputtering, which contributed over 80% of the total impact in most cases. Some simple, sputter-free materials showed very low impacts, while multilayered designs had much higher impacts. A Pareto front optimisation highlighted three materials that balanced cooling efficiency with lower environmental impact, though the results are highly sensitive to assumptions. The six newly developed PMC compositions were then assessed using the same method. Two compositions had a low impact comparable to the best existing radiative cooling materials, while others, particularly those using an energy-intensive synthesis process with solvents, performed poorly. A full life cycle analysis (LCA) of the new PMC compositions applied to Belgian flat and pitched roofs showed that four compositions have environmental impacts comparable to conventional roofing materials, while the other two, due to faster degradation of their nanofabricated top layer and shorter service life, exhibit significantly higher impacts over time. Dynamic building energy simulations in four cities showed that the new PMC could reduce cooling needs by up to 85% in summer but also increased heating needs in winter. As a result, net energy savings were limited in temperate cities like Brussels and Madrid, even resulting in an increase in associated emissions. In contrast, hot cities with no or limited heating demand, such as Phoenix and Singapore, saw clear cooling benefits resulting in a decrease in annual emissions. Additionally, covering all urban roofs with this material during a five-day heatwave in Flanders and Brussels reduced the UHI by up to 2.7°C, primarily due to increased surface reflectivity. Lower coverage ratios produced little effect, underscoring the need for integrated cooling strategies. Lastly, radiative forcing analysis showed that applying the PMC to all urban roofs in Flanders and Brussels altered the atmospheric energy balance over a five-day heatwave. This change was equivalent to avoiding 822 million kg CO₂ eq. emissions, 2.65% of Flanders' total emissions during that period. This dissertation highlights that while PMC shows strong potential for reducing cooling demand and mitigating urban heat, its environmental performance is highly context-dependent and limited by uncertainties in modelling, climate variability, and evolving material design. A key reflection is the difficulty of fully capturing climate-related benefits, such as urban cooling or radiative forcing, within conventional LCA frameworks, which lack the spatial and temporal flexibility to evaluate such impacts. Methodological gaps remain, particularly in translating physical climate effects into environmental impact metrics like CO₂ equivalents. Future research should focus on developing integrated assessment methods that combine LCA with climate modelling and dynamic energy simulations. Additionally, post-project evaluations, broader climate zone testing, and practical aspects like material durability and cost will be essential for scaling PMC as a viable solution for urban climate resilience.