Smart buildings are more and more common due to recent technological advances. They promise to improve users' lives, but they are packed with sensors that gather user related data, fueling ever increasing privacy infringement suspicions. Captured data usually takes the form of dynamic streams, hence such buildings can naturally be programmed using Data Stream Management Systems (DSMSs) that execute long-running queries on data flowing from sensors. In this paper we address the problem of the dissemination control of private data, encountered in smart buildings. We introduce Tuple-Based Access Control (TBAC), a novel access control model that tracks sensor information flows in a DSMS. We provide users with the ability to enforce easy-to-understand, intuitive security policies on sensor-produced data. When such data are combined by queries in the system, so are their security policies, hence data access control is disseminated throughout the system. We argue that such a model is mandatory to ease the acceptance of smart buildings. Nevertheless, TBAC can also be relevant to other scenarios involving dissemination of aggregable private data.