An explorative method to support design decisions based on carbon constraints and daylight sufficiency needs

The global construction industry contributes to 37% of carbon emissions associated to both building operations and construction. To help achieve the net-zero targets set by 2050, it is mandated to achieve a 50% reduction in carbon emissions by 2030. As we strive for low-carbon buildings that align with these targets, it is imperative to ensure buildings remain comfortable for their inhabitants. Daylight serves as a crucial component in this regard, not only providing illumination and enhancing well-being but also influencing the whole life carbon emissions. The existing standards as minimum daylight levels tend to encourage larger glazed areas, which often result in larger solar gains in the summer and heat losses in the winter. To avoid these, often larger shading systems, thicker frames and multiple panes of glass are required to respect operational energy targets. These imperatives in turn influence the embodied impact of the building as a result of the facades material and components choices. Amongst these various inter-relationships, there has been a great level of attention dedicated to the operational energy use associated with daylight-driven decisions, while the interactions between daylight strategies and whole life carbon impacts remain unexplored. This research aims to uncover the interactions between daylight performance and whole life carbon analyses. It proposes a novel methodology to support daylight-driven decisions based on these interactions and under carbon budget constraints in early design stages: this is indeed the stage at which the overall daylighting strategy is usually defined. The method integrates explorative life cycle assessment, daylight simulations, target cascading and a sensitivity analysis approach, and aims to facilitate decision-making in early stages of design with a focus on building facades. Through an application of the method to different residential building archetypes and a lab usability testing, the decision-making potential of the proposed method is demonstrated. This evaluation emphasizes the capacity of the proposed method to provide design guidance on the whole life carbon consequences of daylighting strategies early on, when the design space to explore is still broad, and promoting solutions that would account for the delicate equilibrium between the two.