Construction of commercial buildings has an environmental impact because of emissions from nonroad equipment. Construction produces 7% of the U.S. greenhouse gas emissions, of which 76% originates from engines. However, there has not been an established methodology for estimating construction activity emissions at the project level for buildings and other constructed facilities. Therefore, determining where and when construction produces emissions is important, necessitating that emissions inventories (i.e., databases of project emissions by type, cost, etc.) be developed to quantify these emissions. The pollutants addressed in this paper include carbon dioxide (CO2), nitrogen oxides (NOx), total hydrocarbons (THC), carbon monoxide (CO), particulate matter (PM), and sulfur dioxide (SO2). This paper presents a methodology that provides a direct link between building construction activities and emissions. The use of this methodology is demonstrated for a commercial building case study, thereby providing quantified emissions predictions for various levels of detail (i.e., construction activity, construction cost division, and overall project). Using this methodology, both fuel use and emissions can be determined at any stage of the planning, designing, and building process with increasing levels of precision being obtained as the project progresses. The methodology demonstrates the ability to link key quantitative indicators of specific building construction activities to emission rates for specific types of equipment used in construction. The case study results illustrate that emissions during construction are highly episodic, with site work activities and equipment contributing large proportions of overall project emissions.