Impact of passive energy efficiency measures on embodied and operational GWP: A parametric study of detached houses under evolving grid and climate conditions

This study re-evaluates detached-house decarbonisation strategies, focusing on the interactions among passive design strategies, including structural materials, architectural form, and thermal insulation. The large-scale parametric analysis of 496,800 models shows that among the 8 passive design measures considered, those related to the U-value, shape, and material of the load-bearing structure have the greatest influence. Although technological improvements and global warming are projected to reduce heating demand, and grid decarbonisation decreases the carbon footprint, energy efficiency remains a crucial factor. However, excessively well-insulated envelopes (U < 0.15 W/m 2 K) can increase total global warming potential (GWP) on shorter timescales (30 years or less) due to embodied carbon, highlighting the importance of optimising thermal insulation for long-term carbon reduction and passive performance. Based on the evaluated cross-laminated timber cases, we demonstrate that low upfront embodied impact enables greater design freedom, resulting in less stringent insulation requirements and greater flexibility for passive design integration. Nonetheless, the results for brick and reinforced concrete cases show that, besides material choices, shape and energy efficiency are imperative for achieving optimal life-cycle GWP values, with compact models reaching comparative GWP values to those of non-compact CLT models. Ultimately, holistic decarbonisation requires understanding how material choice dictates design strategy: leveraging low-embodied materials to expand design possibilities and enhance passive performance, while requiring compactness for high-embodied ones to achieve long-term carbon reduction and minimise reliance on active systems.