The importance of building automation and control systems (BACS) in modern automated buildings is constantly growing. Increasingly, these systems are responsible for functions directly or indirectly affecting people's safety, security and health. Thus, the respective technology is supposed to be developed in a way that requirements of the two most important features are met: functional safety and system security of both the network nodes and the communication protocols. Hence, a common approach to develop a safe and secure BACS is presented. It is based on a lifecycle model that defines requirements for the different stages of the system life. The common approach is harmonizing safety and security discipline by using methods specified in two international standards: IEC 61508 for safety and Common Criteria for security. The special focus of the thesis is on the commonalities between the development of safety and security systems and how to benefit from these commonalities in development. There are similar goals, requirements and related measures to safeguard the system. And a way of dealing with inevitable contradictions is outlined by introducing a conflict resolution approach.