Reinforced concrete (RC) is one of the structural materials that produce environmental pollution. The objective of this study is to present design guidelines for reducing CO2 emissions or costs associated with structural materials in the structural design phase of RC columns. After identifying the cross-sections of RC columns with the minimum CO2 emissions or costs while satisfying the structural design conditions via a parametric study, the influence of the design factors (i.e., concrete strength, steel reinforcement strength, cross-section size, and amount of steel reinforcement) on the CO2 emissions and costs of RC columns are investigated. The results confirm that increasing the strength and amount of steel reinforcements is efficient for sustainable design, whereas increasing the strength of the structural materials and the amount of concrete is efficient for economical structural design. (C) 2014 Elsevier B.V. All rights reserved.