AbstractBuildings are vulnerable to extreme winds, both physically and functionally. Although many studies exist on buildings’ structural and interior damage modeling, limited research exists on the modeling of buildings’ functionality loss under extreme winds. In this paper, a novel probabilistic building functionality estimation framework is developed to quantitatively evaluate the functionality of buildings under hurricane winds. The functionality of a building is evaluated by integrating the functionalities of individual building systems (e.g., envelope, interior, electrical, and HVAC) that are determined by a detailed component-level damage analysis considering uncertainty in wind loading, rain ingress, and component resistance capacity. The proposed framework is demonstrated with a 1-story wood residential building by estimating its shelter function. The fragility curves are developed for multiple functionality states of the shelter function and compared with the fragility curves developed for the envelope system only. The comparison indicated that the functionality of a building evaluated by considering the four building systems was significantly lower than the functionality evaluated by considering only the envelope system. Thus, considering the envelope system only will largely underestimate the building functionality loss.