We use a recovery heat exchanger (RHE) in an industrial building to heat incoming air for space heating by using the heat contents of some of the refuse hot-air flows (RAF). Several RAFs are often available with different flow rates and temperatures. A proper scenario for use of their heat contents is essential for efficient management of the energy system. Using a steady-state, bottom-up approach, we have obtained a set of equations that we have linearized. Linear programming (LP) is then used and LINE software has been developed. This software has been used for an industrial building with three RAFs to obtain a use scenario corresponding to the highest energy-saving efficiency and minimum life-cycle costs of the RHE. Depending on the RHE size, temperatures and flow rates of the RAFs, and the outside temperature, we can recover the heat contents of different RAFs in different ways.