Building Management Systems (BMS) monitor and control smart buildings. We are witnessing a trend of BMS becoming increasingly sophisticated and delivering more advanced services. The downside of this is that the complexity of BMS is also increasing, thus, making smart buildings vulnerable to various malfunctions and faults. We anticipate that reliability of smart buildings will be gaining in importance, especially for BMS of critical buildings, such as hospitals or buildings that host emergency services or store sensitive materials or technologies, whose unreliable operation could have catastrophic consequences. The assistance, however, is in the large amounts of easily available data that implies possibilities for development of highly accurate reliability models. Cloud computing can be also utilized to support collaborative sharing and benefitting from each other building's data. To utilize all of the above stated, we have developed a cloud-based BMS reliability analysis framework that we describe and illustrate in this paper.