1. A building system, comprising: a) a communication network; b) a plurality of wireless nodes within a building operably coupled to the communication network; c) a plurality of passive wireless devices, each passive wireless device affixed to or within an object within the building, each passive wireless device containing first information regarding at least one thermal property of the object, each of the passive wireless devices configured to communicate wirelessly to at least one of the wireless nodes using power derived from communication signals detected in the passive wireless device; d) a processing circuit operably coupled to receive the first information from the wireless devices, the processing circuit configured to generate a model of at least a portion of a building based at least in part on the thermal property of the object.