A building management system (BMS) includes one or more sensors that measure a variable state or condition in the BMS and a plurality of BMS devices that operate to affect the variable state or condition measured by the one or more sensors. Each of the BMS devices stores a thermodynamic block that models the BMS device. Each of the thermodynamic blocks includes a list of connections and a list of stats. The connections define one or more inputs to the thermodynamic block and one or more outputs from the thermodynamic block. The stats define one or more relationships between the inputs and the outputs. Each of the BMS devices includes a solver configured to perform calculations using the stats and connections defined by the thermodynamic block stored within the BMS device.