An input/output module for a building automation system includes a mounting plate, a circuit board, and a cover. The mounting plate has at least two fastener receptacles (24-30) positioned to align with fastener receptacles of a standard electrical junction box (90). The mounting plate further includes at least two openings, each opening sized to receive one or more wires therethrough. The circuit board supports an interface circuit configured to communicate on a building network. The circuit board also includes device input terminals and device output terminals. The interface circuit is configured to provide an interface between the building network and devices connected to the input and output terminals. The circuit board is configured to be mounted to the mounting plate. The cover is sized to fit over the mounting plate and circuit board.