Thermal and daylighting performance of representative spatial configurations in contemporary Japanese municipal office buildings

Department of Architecture and Urban Design, Faculty of Regional Design Science, Utsunomiya University, Utsunomiya 321-8585, Tochigi, Japan

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Abstract

Abstract. Recent Japanese municipal office buildings commonly feature elongated floor plates, large south-facing façades, and double height atria intended to enhance daylight availability and public transparency. Although these spatial configurations are widespread, their combined effects on indoor environmental quality remain unclear. This study examined two representative spatial configurations extracted from a nationwide survey of contemporary municipal offices: a perimeter office with glazing on a single exterior façade and a double height atrium connected to a south-facing façade. A computational fluid dynamics analysis evaluated thermal behavior under representative summer and winter conditions, while a climate based daylighting analysis assessed illuminance by depth and visual uniformity in atrium adjacent zones. The thermal results indicate pronounced summer overheating in west-facing perimeter offices, moderate warming in south-facing orientations, and relatively stable temperatures in north- and east-facing offices, with limited seasonal differences in winter. The daylighting analysis revealed clear depth related contrasts: the middle and rear zones achieved high illuminance levels but exhibited low uniformity and strong temporal variation, whereas zones near the façade maintained more stable but lower illuminance levels. These results suggest that façade connected atria can generate competing thermal and daylighting responses. This study provides performance based insights for integrating façade design, shading strategies, and atrium configuration to improve indoor environmental quality in public-sector buildings.