Indoor-outdoor visual connectivity studies focus on analyzing view vectors and their spatial distribution, considering the three-dimensional nature of visual perception. Typically, these studies use the observer's position as a focal point from which view vectors radiate outward. However, they often overlook the multiple positions an observer can occupy in space and the various relationships these positions create with the façade system, leading to differing visual connections to the outside environment. Specialized studies that analyze multiple observer positions provide valuable insights by mapping visual connections for each location. However, they tend to lack a singular metric to assess indoor-outdoor visual connectivity as a factor influencing visual performance in relation to the space and façade system.

This article introduces the Visual Connectivity Index (VCI)—a metric designed to evaluate indoor-outdoor visual connectivity. VCI measures the relationship between a façade system and the indoor space it encloses, assessing how uniformly and seamlessly the interior connects to the exterior through the façade system while considering multiple observer positions. VCI contributes to three key areas: (1) It enables the evaluation of a façade system’s impact on visual connectivity and its interaction with enclosed space; (2) It provides a performance-based measure of visual connectivity (3) It facilitates the comparison of alternative design solutions within the framework of architectural design.

By synthesizing the complex phenomenon of indoor-outdoor visual connectivity with the role of the façade in shaping this relationship, Visual Connectivity Index (VCI) presents a novel and valuable approach that has not been previously explored. To demonstrate its application, this study systematically compares the performance of 20 design alternatives across three different façade systems, resulting in a total of 60 iterations. The results indicate that VCI is sensitive to various design options, enabling a thorough evaluation of different architectural design choices.