Smart buildings are run by Building Management Systems (BMS) that are cyber-physical systems that control and monitor a number of buildings' subsystems. BMS have not been sufficiently prioritized on their reliability measures. Reliability, however, along with security, safety, energy performance and occupant comfort, are very important for certain classes of BMS [1]. This is especially true for BMS of critical buildings, such as hospitals or other buildings that host emergency services. The same would apply to buildings that store sensitive materials (e.g. certain biochemical substances) or technologies, where buildings' unreliable operation could have catastrophic consequences. With the convenience and ease of obtaining data at present, reliability analysis of BMS can be substantially supported and enhanced. Furthermore, cloud computing can be utilized to support collaborative sharing and benefiting from each other building's data. To utilize all of this, we work towards cloud-based BMS reliability analysis framework, and describe our concept¹.