Analytical modelling, controller design and simulation of an air-to-air runaround coil heat recovery system are studied. The system consists of two plate-fin-tube coils, a storage tank, two circulating pumps, an auxiliary heater and associated distribution network. Simulation results showing the transient response characteristics of the open-loop and closed-loop system are given. Results show that the designed controllers are able to hold the preheat temperature and the storage tank temperature at their respective setpoints irrespective of changes in outdoor and exhaust (source heat) temperatures.