A growing number of manufacturing industries are initiating efforts to address sustainability issues. A study by the National Association of Manufacturers indicated that the manufacturing sector currently accounts for over a third of all energy consumed in the United States. There are many areas and opportunities to reduce energy costs and pollution emissions within a manufacturing facility. One way to achieve an energy efficient manufacturing system is to measure and evaluate the combined impact of process energy from manufacturing operations, their resources (e.g., plant floor equipment), and facility energy from building services (e.g., ventilation, lighting). In this paper, issues associated with integrating production system, process energy, and facility energy to improve manufacturing sustainability are explored. A modeling and simulation case study of analyzing energy consumption in a precision casting operation is discussed. 1 INTRODUCTION A driving force behind sustainable manufacturing is cleaner and more efficient production. The U.S. Department of Commerce defines sustainable manufacturing as "the creation of manufactured products that use processes that are non-polluting, conserve energy and natural resources, and are economically sound and safe for employees, communities, and consumers." Sustainable manufacturing covers a wide range of concepts, including profit, environmental impact, product life cycle, user experience, recyclability, etc., but currently energy consumption commands great attention since it improves both the bottom line and the environment. Energy management is challenging for manufacturing due to the difficulty that arises from the diversity of energy use-there are thousands of processes, each having unique energy consumption characteristics as well as different production requirements based on the product, product quality, environmental compliance, and other business factors (U.S. Congress, Office of Technology Assessment 1993). The motivation for striving for more energy efficient manufacturing is well-documented. It is estimated that manufacturing in the United States uses one-third of all the energy consumed (U.S. Department of Energy 2004). Considering that buildings constitute about 39 % of all energy use, a substantial portion of manufacturing energy use is attributable to the building facility apart from any manufacturing activities. Thus, to achieve sustainable manufacturing, one must consider the energy consumption impacts of both production and the associated factory. Given these energy numbers, the smarter integration of production system, process energy, and facility energy data presents a clear-cut opportunity to improve manufacturing sustainability (Arinez and Biller 2009). Integrating the knowledge of the process and facility is critical for achieving more sustainable manufacturing operations. Unfortunately, production and facility energy relationships are modeled in a suboptimal way. Part of the problem can be attributed to the functionality schism between energy m...