Evaluation of Steady-State Volumetric Heating Load Methods Considering Building Envelope Type and Window-to-Wall Ratio

Recent studies have shown that building-envelope characteristics, including thermal mass and window-related solar gains, can significantly influence heating load behavior. However, their implications for the applicability and accuracy of simplified volumetric heating load methods remain insufficiently understood. Therefore, this study evaluates the applicability and accuracy of steady-state volumetric heating load methods under varying envelope conditions. Representative residential building models with different envelope types and window-to-wall ratios (WWRs) were analyzed. Heating loads were calculated using a normative volumetric approach based on tabulated specific heat-loss coefficients (Method 1) and a recalculated approach incorporating envelope characteristics and solar gains (Method 2). A comparison at hourly, peak-load, seasonal, and load-duration-curve (LDC) levels revealed that the performance of steady-state volumetric methods is strongly dependent on both envelope characteristics and the level of heating load assessment. Method 1 consistently overestimated seasonal heating demand by 41–218%, whereas Method 2 substantially reduced the error. However, Method 2 still underestimated annual heating demand in highly insulated buildings (up to 39%) and peak heating load (up to 63%). These findings indicate that the applicability of volumetric methods depends on both envelope characteristics and the level of heating load assessment. The results highlight the importance of accounting for envelope-dependent thermal-mass effects when applying volumetric methods to hourly, peak-load, seasonal, and LDC-based analyses.