Value-Based Conceptual Modeling of Costs and Embodied Carbon for Building Structural Systems: Mass Timber Perspective

Abstract

Construction product manufacturing is a major contributor to the global climate change through its carbon emissions, known as embodied carbon (EC). In response, previous studies have found that utilizing a structural system of mass timber and cross laminated timber panels (CLT) can contribute to reduction of EC in the construction industry, when compared to other conventional structural systems. However, a major barrier that prevents the use of mass timber CLT is its higher cost than other available alternatives. In other words, project stakeholders that wish to reduce EC in their projects must justify the extra expense of selecting mass timber CLT. One method to achieve this justification is to demonstrate the value of such a decision. In that, quantifications of costs and reduced EC are needed to show the value by answering how much EC is reduced and how much does it cost. However, there is a dearth of studies aimed to develop an efficient framework to support the quantifications for value determination. The current practices require a significant amount of time and resources, which can cause project stakeholders to forgo the effort. To fill this knowledge gap, the objective of this project is to develop a new method, called the construction carbon reduction value model (CCRVM), which aims to improve the accessibility of structural system EC and construction cost data by streamlining the process of quantification and value determination. This is accomplished by automating the quantification steps and visualization of the data. To test the validity and usability of the CCRVM, a case study was performed to compare the costs and EC of four separate structural system alternatives based on a new university classroom building. Through the case study, the CCRVM proved to be an efficient and effective way of quantifying and comparing the costs and EC of the chosen alternatives. The case study findings show that structural alternatives that utilized mass timber CLT resulted in a percentage increase in construction costs but a much larger percentage reduction in EC. The CCRVM is expected to be an asset to project stakeholders that wish to lower EC by selecting mass timber CLT for their structural system. In addition to this it contributes a framework that can be used to test the EC and cost of other construction materials as well.