3D façade geometry as a dual passive control in hot urban canyons: reducing street MRT and cooling loads

Both horizontal and vertical surface characteristics shape urban microclimates in hot‑summer cities. Although recent attention has turned to three‑dimensional (3D) façade geometries, their simultaneous quantitative impact on both building cooling energy and pedestrian thermal comfort has not been established. We simulate five façade morphologies, flat, pixelated, wedge, carved, and wavy, within a controlled Mediterranean canyon (H/W = 1.0, Nicosia, Cyprus) and compare summer heat conditions. A Honeybee–EnergyPlus–Radiance workflow, bench‑checked under laboratory conditions (MBE + 0.06 °C; CV(RMSE) 3 %), quantifies peak wall surface temperature, pavement conditions, and pedestrian‑level mean radiant temperature (MRT), Universal Thermal Climate Index (UTCI) hours and buildings’ annual cooling energy. 3D façades reduced peak wall temperature by up to 8.5 °C and annual cooling energy by 9–16 % under the current climate, with energy benefits narrowing to 6–9 % under RCP 8.5. Orientation is critical: in north–south canyons, 3D forms lowered peak pedestrian MRT by 4.7 °C and reduced UTCI “Very Strong” exposure by 9 percentage points. To contextualise the magnitude of these geometry driven effects, the discussion reports indicative ranges from established façade scale passive strategies. Compared with material‑based interventions, 3D forms slightly outperformed green façades (cooling efficiency up to 16 % vs 7–15 %) and matched retroreflective coatings for pedestrian comfort (MRT relief of 3–5 °C). These findings provide an evidence‑based foundation for the orientation‑specific deployment of 3D geometry as a passive, climate‑responsive envelope strategy.