This work investigates the impact of interface geometry between concrete and insulating layers on the energy performance of building walls. A numerical efficient two-dimensional transient heat transfer model based on finite differences with the dufort-frankel scheme and the Ghost Fluid Method is developed to simulate annual wall thermal response. Interface shapes are parametrically defined using explicit mathematical functions and particle-based approaches, including b & eacute;zier and Radial Basis Function curves, and optimized using the NSGA-II genetic algorithm. The approach is applied to a double-layer building fa & ccedil;ade with external insulation under spatially and temporally heterogeneous boundary conditions in urban street canyon environments. Several studies assess the influence of interface parametrization, identify the most suitable representation, and extend the analysis to multiple street canyon configurations across metropolitan France. Results demonstrate that optimized interface geometries can significantly improve annual energy efficiency and that optimal shapes are highly sensitive to environmental conditions.
Buildings' thermal mass provides energy flexibility to support power grids with increasing shares of renewable generation. Since the amount of shiftable energy varies with boundary conditions, a reliable time-dependent quantification is required. This study proposes a framework to assess the time-varying energy flexibility of building thermal mass using the flexibility envelope metric. Unlike existing works, which either rely on simplified control-oriented R-C models or on detailed models combined with rule-based control, the proposed framework integrates high-fidelity building and HVAC models with a Model Predictive Control algorithm through co-simulation. This approach enables flexibility envelope calculations that jointly capture detailed thermal dynamics and predictive control capabilities. The framework is applied to two residential buildings with floor heating. The results show that simplified R-C based approaches underestimate flexibility in 71% of the evaluated conditions, with an average deviation of -20%. Finally, the storage efficiency ranges between 40%-52% and 46%-55% for the two case studies.Highlights
