Effects of indoor environmental quality on employee productivity and performance are well established in literature. However, further justification and quantification of costs for maintaining optimal indoor conditions for maximized employee productivity are necessary. This paper presents graphic-analytical approach to investigate the effects of indoor climate on energy consumption and productivity with respect to costs for maintaining optimal indoor air conditions in office buildings. Thermodynamic analysis of air conditioning processes is performed using statistical data for outdoor temperature and relative humidity. The economic evaluation is based on introduction of coefficients describing the price of heating and cooling energy and consumption of water, expressed as heat energy. Results are further plotted on Mollier (h-x) diagram confined with isolines of the levels for the combined energy consumption. Outdoor climate deviation from the optimal indoor air condition increases energy consumption and decreases the profit. Under the extreme outdoor conditions the air handling unit cannot maintain desired indoor temperature and humidity levels and employee productivity decreases, consequently leading to loss in total profit. The proposed approach can be used for optimization of operation of air handling equipment, and determination of maximum economically viable capacities of heating, cooling and humidification equipment, using profit as a criterion.