Carbon budgets at the component scale and their impacts on design choices: the façade as a case study

In accordance with the Paris agreement, the Swiss Climate Strategy (SCS) defines the net-zero target to be reached before 2050, which demands for a thoughtful carbon budget allocation between the different contributors. Ongoing normalization tasks are currently defining life cycle carbon budgets at the building scale aligned with the SCS. While recent research has provided promising methodologies to break down a whole building’s carbon budget, SCS-aligned budgets cannot be calculated at the component scale yet. Having the ability to define carbon budgets at the components’ level could support a carbon-responsible design process by reducing the scope of the design problem: the idea is to ensure that the cumulative impact of all the building components (calculated per building energy reference area) remains below the allowed building carbon budget based on SCS targets. This would provide a straightforward link between SCS and carbon budgets at the component scale, a scale at which many decisions need to be taken during the design process. Moreover, based on the set SCS net-zero objectives to be reached by 2050, the carbon budget, whether for buildings or for their components, will have to decrease annually, thereby affecting design flexibility, i.e. the number of design solutions that can still comply with the building's carbon budget on any specific year. The research presented in this paper aims to provide a framework able to set carbon budgets at the components’ scale and start discussing the consequences of such carbon budgets on façade design flexibility until 2050.