Building Automation System (BAS) will be extended for including different kinds of information, working towards to goal of Intelligent Building Management System. The next generation of Internet technology uses Windows Communication Foundation as middleware technology for integration of different building automation systems (BAS) since Web Services will support only http protocol which is stateless. The applications used for controlling building management system (BMS) components like sensors, actuators, and controllers. In this paper we propose a Service Oriented Architecture(SOA) for building Management system based upon Windows Communication Foundation and XAML used for integrating different BAS.A BAS which consists of BACnet network their BMS is applied. Their exist some publically exposed Windows Communication Foundation contracts, which write and read BACnet data points from the backnet work. 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. XAML will be provided at client side GUIs for the BMS which can be reused for different kinds of applications. Finally we discuss challenges in providing security to Building Automation Systems using proposed system.