Building Automation is one of the critical issues in recent scenarios. The process of Building Automation is called as Building automation System (BAS).The BAS includes different kind of information that enables to work towards intelligent building system. There was a Web Services technology for integrating different BAS but it supports only HTTP protocol which is stateless. This paper presents the next generation internet technology Windows Communication Foundation (WCF) to integrate different building automation systems in the development of BAS. WCF includes various contracts which writes and reads Building Automation Control Network (BACnet) data points from BACnet network. These contracts will be called by other enterprise applications for realize BAS integration and get real-time data on BACnet network as a facilities Management.BMS will be applied in a BAS which consists of BACnet network. The applications use sensors, actuators and controllers for controlling Building Management System (BMS). This paper presents a Service Oriented Architecture (SOA) for BMS using WCF and Extensible Application Markup Language (XAML) which will provides client side GUI for BMS reused for different kind of applications. Finally, it discusses about challenges in providing security to BMS. © 2011 Springer-Verlag.