A sensor system for a building, the sensor system comprising a plurality of sensor units and a processing unit wherein the sensor units each comprise a plurality of electronic components which are provided either directly or indirectly via a substrate, on a surface of an external component of the building, or embedded within an external component of the building; and wherein each sensor unit comprises a sensor operable to monitor a building parameter; and a communication module operable to output a signal comprising data indicative of the monitored building parameter to the processing unit.