Wireless sensor-actuator networks can bring flexibility to building control. We develop a building control prototype system to exhibit how to apply the wireless sensor-actuator networks technologies to the building control. The general purpose is energy saving and emission reduction through the collaboration among a mass of lowcost sensor nodes and actuator nodes. In this paper, we detail the hardware and software in our building control prototype system, and then we address the following key technical challenges: (1) a lightweight trust management framework for discrete data; (2) self-adaptive audio sampling and combining reception algorithm; (3) hierarchical synchronization strategy. Finally, a set of experiments are presented to evaluate the performance of our key technologies.