An integrated approach was used to optimize energy use and expenditure of a RC-network model for five zones (four perimeters and one center zone) office building to control dimmable light, shade position, inside air temperature, and outside air flow rate. Parameters considered in this model were: (1) heat transfer, solar heat gain, and illuminance from window; (2) heat transfer from internal and external walls; (3) external walls heat storage; (4) internal heat gain from occupants and equipment; (5) ventilation rate; (6) cooling and heating systems load; and (7) illuminance and heat gain from artificial lights. Total energy consumption of artificial light, ventilation fan, heating and cooling systems was considered as objective function for optimization. The multi-hour optimization included minimizing total energy use and expenditure for single- or several-hour periods. Our analysis showed significant energy saving potentials by using building integrated multi-hour optimization. Comparing total energy use of the building assuming fixed control schedules with the integrated control of the systems showed yearly savings nearly 35% in electricity use for the simulated office building. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.