The effect of surrounding topography on calculated solar gains in BEM using DEM-based terrain reproduction

Abstract

This paper presents a methodology for integrating the orographic context of micro-locations into building energy modelling (BEM) for topographically diverse regions. Dynamic energy simulations rely on high-resolution weather data from weather stations that represent specific areas. When the micro-location of the simulated building differs from the weather reference site, topographic shading can trigger deviations. This study developed a three-dimensional reproduction of the micro-location’s surrounding terrain as a simplified ring model, based on horizon height data retrieved from a Digital Elevation Model (DEM). Within a 20 km radius, four Slovenian cities from the same weather-representative area were analysed and compared with a baseline calculation. When comparing solar gains (SG) at selected micro-locations using average elevated horizon angles, a clear tendency emerges: the lower the Sky-View Factor (SVF), the greater the SG deficit. By capturing the elevated horizon more precisely through the proposed methodology, the results demonstrate that—depending on azimuthal orientation and barrier height—solar gains may vary by up to 12% even for locations exhibiting nearly identical SVF values. This approach improves the precision of BEM in topographically diverse regions and can inform better design and planning decisions.