Metrics are instrumental in design assessments. Solar performance metrics help designers to evaluate solar access in cities. Metrics should be used early in the urban planning stages in order to enable sustainable urban development with greater access to solar energy. Currently, solar assessments at this design stage are limited in practice; established methods or routines are lacking, and so are suitable metrics. This paper reviews the relevant literature to provide a critical overview of solar metrics commonly used in building performance assessments. The review defines key metric formulation principles—valuation, time constraint, and normalisation—which should be considered when designing a performance indicator. A new taxonomy of solar performance metrics is provided. Metric definitions, suitability, and limitations are discussed. The findings highlight the need for reliable, low-complexity metrics and adequate methods for early solar assessments for urban planning.

Solar access describes the capacity of urban spaces to receive sunlight and daylight. Rapid urbanization and unbridled densification pose a threat to sustainable solar access, reducing the penetration of sunlight and daylight into cities. To effectively assess solar access at such an early design stage, at the urban planning level, it is critical that evaluation metrics are simple and reliable. This paper examines a cross section of solar metrics, from simple to more complex ones, to find potential solar performance indicators for urban planning evaluations. The metric datasets were created based on iterations of homogeneous neighbourhood designs, based on the three commonest typologies in the Swedish context: courtyard, slab, and tower. The results were validated using case studies sampled from districts of Malmö. The findings indicate that simple geometrical and latitudinal metrics may be suitable for assessing the solar access of urban designs due to high correlation with built density. Potential performance indicators aimed at indoor and outdoor evaluation of daylighting (VSC, SVF) and sunlighting (ASH_F, RD_G) in urban planning stages were suggested. Possible methods of applying the provided metric database into assessments were proposed. Future work should find evidence-based thresholds for the metric values to establish performance benchmarks.

This paper explores the relationship between the Vertical Sky Component (VSC) metric and the European and Swedish daylighting regulations. VSC, a static geometrical metric, is considered a useful early indicator of indoor daylighting, as it is insensitive to late-stage design details such as material properties and internal layout. However, its relationship with modern building daylighting legislation has not been established. To address this gap, the paper investigates the relationship of VSC and daylight compliance by static and dynamic methods through simulations of a ‘shoebox’ room with varying Window-to-Floor Ratios (WFRs) and external obstruction dimensions. The results demonstrate that VSC has a large effect on daylighting compliance and can be a useful early planning tool. The study concludes that using VSC as a daylighting indicator in the urban planning process can lead to improved early design routines for better daylight compliance in the late design stages. Future work should aim to establish VSC performance thresholds.