A renovation project generally requires time, money, or costly equipment to examine the existing conditions of a structure. When unforeseen existing conditions are not properly examined, unexpected costs and/or schedule impacts can adversely affect the successful completion of a renovation project. This paper examines whether the cost impact of change orders due to unforeseen existing conditions is significant compared with the cost impacts of all other change orders, and quantifies the impact on the total project costs and the construction trade. Statistical analyses such as $t$ -test and ANOVA were conducted, using information on 517 change orders obtained from 27 building renovation projects. The results show that change orders due to unforeseen existing conditions have significant impacts compared with change orders caused by other reasons, and that the calculated mean cost is higher for change orders stemming from unforeseen existing conditions. The results also show that the concrete trade is most impacted by change orders from unforeseen existing conditions, while the trade with the highest cost impact is heating, ventilating, and air conditioning. This paper investigates the effect of unforeseen existing conditions on the costs associated with change orders. The paper also identifies those construction trades that are more impacted than others and, therefore, require special attention. This knowledge is essential for identifying areas of possible cost overruns and minimizing overruns in building renovation projects.

CO₂ emissions account for 80% of greenhouse gases, which lead to the largest contributions to climate change. As the problem of CO₂ emission becomes more and more prominent, research on sustainable technologies to reduce CO₂ emission among environmental loads is continuously being conducted. In-situ production of precast concrete members has advantages over in-plant production in reducing costs, securing equal or enhanced quality under equal conditions, and reducing CO₂ emission. When applying in-situ production to real projects, it is vital to calculate the optimal quantity. This paper presents a dynamic optimization model for estimating in-situ production quantity of precast concrete members subjected to environmental loads. After defining various factors and deriving the objective function, an optimization model is developed using system dynamics. As a result of optimizing the quantity by applying it to the case project, it was confirmed that the optimal case can save 7557 t-CO₂ in CO₂ emissions and 6,966,000 USD in cost, which resulted in 14.58% and 10.53% for environmental loads and cost, respectively. The model developed here can be used to calculate the quantity of in-situ production quickly and easily in consideration of dynamically changing field conditions.

Green planning is critically important during the design phases of construction projects but continually gets less attention during construction. Project owners and planners need to understand how communication influences green implementation. To address a gap in the extant research, this paper presents the evaluation results on how sustainability awareness of field supervision personnel impacts the successful completion of school projects by proving that communicating sustainability goals with them is vital for decision-making during the construction stage of the project. This paper uses data collected from 162 new school construction projects to compare sustainability design goals with their successful incorporation into completed projects. Seventy-one project managers and inspectors were surveyed to assess their awareness of key high-performance sustainability requirements that were built into the designs. The responses from these two groups were compared to examine the positive or negative impacts. The analysis results show that early and continuous communication of sustainability design goals with field supervision personnel has a significant impact on whether those goals are realized when the project is turned over to the owner for occupancy. Successful implementation of sustainability goals not only provides economic benefits from fully exploiting life-cycle costs, but also holds the promise of providing a healthier working environment.