Uncertainty of solar radiation in urban canyons propagates to indoor thermo-visual comfort

The incident solar radiation on building facades is strongly affected by the urban characteristics, however frequently overlooked in the assessment of indoor environments due to limited data availability. Here, we show that a simplified representation of the urban environment can drastically affect the estimation of the incident solar radiation within urban canyons. We associate uncertainties with the canyon’s geometry, built surfaces, optical properties, as well as vegetation, and resort to a hybrid probabilistic-possibilistic approach to quantify the effects on thermo-visual comfort. Contrasting complex against simplified urban canyons shows that the pattern of incident solar radiation is uneven along the building façade and strongly correlated to the canyon’s characteristics. We also demonstrate that simplified models of urban canyons could underestimate the number of thermally comfortable instances by even 365 h a year (i.e., ~ 4% of the time). Similarly, a simplified canyon underestimates the visually comfortable occurrences, especially during the intermediate seasons. While a simplified canyon estimates a glare probability of 1.0, uncertainties within a complex canyon can lower the glare probability to 0.28 throughout the day. We show that for visual comfort, geometric characteristics alone, such as the canyon’s skyline, can outweigh optical properties such as the transmissivity of trees. This uncertainty, especially in the estimate of glare probability, may lead to different decisions about building envelope design, including the need for a more or less adaptable façade.