The energy impact on retrofit of existing buildings has forced the building owner to seek more sophisticated energy conserving techniques other than the common sense measures that were taken. Computer control of the heating and cooling processes in buildings enable implementation of more sophisticated techniques of conservation and to include integration of stand alone algorithms. The integration of fan system optimization routines such as enthalpy control and reset of cooling coil from the zone of highest demand with floating space temperature provide new opportunities for reduced energy consumption. Each one of the stand alone algorithms is simulated in details including the dynamics of the building structure, mechanical system, and control. The integrated approach is also simulated and daily temperature and energy profits are generated. The annual saving of the fan system optimization algorithm with floating space temperatures are calculated for buildings on the campus of San Diego University. The energy saving is also calculated for systems with fixed minimum outside air and variable intake of outside air.