The construction industry is one of the main contributors to the production of large volumes of greenhouse gases, since it consumes a large quantity of energy and construction materials. The purpose of this research is to assess the environmental impacts and economic efficiency of the voided slab system compared to the ordinary reinforced concrete slab. A life cycle assessment (LCA) and the total cost of construction were calculated to evaluate the performance of both slab systems. Additionally, the total costs of construction for both cases were determined based on the unit price of the building materials. The results of this study indicate that manufacturing building materials contributes most to the total GHG emissions where concrete is responsible for nearly 1/2 of all emissions. Additionally, forms are the second largest contributor of the total GHG emissions and account for nearly 40% and 15% of emissions for the ordinary reinforced concrete slab and the voided slab system, respectively. This study verified that the voided slab system indicated better environmental performance than the ordinary reinforced concrete slab. The total GHG emissions of the ordinary reinforced concrete slab were 256,599 and 13,989 kg·CO2·eq, for concrete and forms, respectively. Additionally, the total GHG emissions of the voided slab system were 224,945 and 12,211 kg·CO2·eq. The reduction of GHG emissions from Case 1 for aboveground floors and Case 2 for underground parking was 12.3% and 12.7% over the ordinary reinforced concrete slab, respectively. The economic efficiency of the ordinary reinforced concrete slab and the voided slab system were assessed by comparison of the total costs of construction. This showed a total cost reduction of 12.3% and 11.2% for the case of applying the voided slab system to the aboveground floors and underground parking, respectively. Thus, replacing the ordinary reinforced concrete slab by the voided slab system in the aboveground floors and the underground would make it possible to decrease not only the emissions of GHG, but also the cost of construction.
