Minimal research has been conducted to develop non-invasive processes for quantifying and evaluating worker mental workload - a critical concern - at the task level in the construction industry. One reason for this gap in research is the complex and dynamic nature of the construction process, which makes construction work more complicated to measure and predict compared to work in other industries. This paper presents a novel approach and corresponding conceptual model to quantify and evaluate construction worker perception of mental workload at the task level using the energy concept. A conceptual process for assessing mental workload (MWL), i.e., the feeling of stress, pressure, and being overwhelmed due to the task nature, factors, conditions, and resources that accompany the performance of the task, was developed from extant research and interviews. The Delphi method was utilized to characterize the energy-based model and provide initial verification. The results from the literature review, expert insight, and four rounds of the Delphi survey revealed 14 constituents, 51 components, and one metric for each component to measure the level of MWL felt by a worker. These constituents, components, and metrics were used to develop a model for measuring construction worker MWL. This study contributes to knowledge by developing a novel non-invasive method for assessing potential task-level MWL using an energy-based model. The energy-based assessment model contributes to practice by providing a tool that could be used to measure the potential impact of construction tasks on workers perceived mental workload.
