A cost-optimal analysis for nearly zero-carbon timber building solutions in line with the EPBDrecast 2020 for Belgium = Multi-objective optimization, Life Cycle Cost, Life Cycle Carbon, Nearly Zero Carbon Buildings, Timber, Green Building

Europe has set carbon reduction targets, aiming for a 55% decrease in emissions by 2030 and carbon neutrality by 2050. The construction sector faces regulations under the Energy Performance of Building Directive recast 2020, which requires all new buildings to be Zero Emission Buildings (ZEBs) by 2030. Anticipating stricter regulations, such as Nearly-Zero Carbon Buildings (NZCB), the focus will shift to the entire lifecycle emissions. Bio-based materials, like timber, will likely replace traditional high carbon footprint materials. A simulation-based multi-objective optimization framework is developed to address the challenge of optimizing building design for minimal carbon impact (LCCO2) at lowest costs. This framework is applied on a case study, with different timber systems, envelope insulations and PV panels parameters as design variables. The set of combinations are effectively explored with NSGA-II, over 4000 simulations. Out of 153 trade-off solutions of Pareto front, 51 optimize the case study, ranging from a reduction of 7% of its LCCO2 at the same cost, to saving more than 63000 €, with a reduction of 1% of LCCO2. CLT and glulam solutions show lower carbon content but higher cost than LVL. Furthermore, embodied carbon results accountable for 48% of total lifecycle carbon on average. The framework, validated by sensitivity and uncertainty analyses, is characterized by high flexibility and adaptability for future use, both academic and professional. However, limitations exist, such as absence of thermal comfort integration. Future research should focus on this limitation, together with expanding the choice of design variables.