• Surface temperature varies with building height, spacing, materials and greenness. • Low-rise factories made of corrugated iron steel are the warmest. • Mid-rise buildings with compact layout display high temperature. • Areas with buildings above 10 stories tend to be cooler than agricultural lands.

• Assess role of techno-scientific expertise in governing urban environmental change. • Evaluate evidence-driven built environment and greenspace policy in Fukuoka. • Epistemic community shapes Fukuoka’s built environment and greenspace policy. • Local history gives favourable context for environmental science in public interest. • Findings nuance understanding of how epistemic communities work at urban scale.