A Study on the Comfort and Energy Effectiveness of Passive Design Method - Case Studies using Detached House Model

Passive design, which harnesses natural forces such as sunlight, natural ventilation, and thermal mass, is increasingly seen as a key strategy for decarbonizing buildings. Conventional evaluations often assume continuous HVAC use and focus on annual energy demand, overlooking the original goal of achieving comfort without mechanical systems. To address this gap, the Thermal Autonomy (TA) metric has been proposed, quantifying the share of occupied hours that remain comfortable without active conditioning. TA provides a complementary perspective to HVAC-based assessments and highlights alternative design priorities. In this study, an extensive parametric analysis was carried out with EnergyPlus for detached houses in three representative Japanese climates—Sapporo, Tokyo, and Naha—by systematically varying insulation thickness, thermal mass, solar shading, glazing properties, and window-to-wall ratios. Building performance was assessed from both active (HVAC loads) and passive (TA) perspectives, enabling a comparative understanding of energy demand and inherent thermal resilience. To examine the relative influence of these parameters, we conducted a Global Sensitivity Analysis (GSA) using two complementary approaches: standardized regression coefficients (SRCs) from multiple regression and SHAP (SHapley Additive exPlanations) values derived from tree-based machine-learning surrogate models. The results revealed that the relative importance of passive design variables differs substantially across cold, temperate, and hot-humid climates, and that the sensitivity rankings change markedly depending on whether HVAC load or TA is used as the evaluation metric. This contrast indicates the need to carefully select performance indicators when assessing passive design strategies. Furthermore, the SHAP-based analysis demonstrated higher predictive accuracy than the SRC-based approach and provided more reliable estimates of parameter influence. The directional SHAP visualizations developed in this study additionally facilitated clearer interpretation of design trade-offs and enabled the identification of key parameters relevant to early-stage design decision-making.Overall, the findings highlight the value of incorporating TA-based assessment and SHAP-enabled sensitivity analysis into the evaluation of passive design strategies, offering a robust and interpretable framework for climate-responsive residential design.