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The U.S. Army Engineer Research and Development Center (ERDC) solves the nation's toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation's public good. Find out more at www.erdc.usace.army.mil.

In this study we analyze the effects of energy efficiency measures on the life cycle primary energy use of a case-study (reference) 4-story wood-frame apartment building using electric resistance heating, bedrock heat pump, or cogeneration-based district heating. The reference building has an annual final heat energy demand of 110 kWh/m 2 . The energy efficiency measures analyzed are improved windows and doors, increased insulation in attic and exterior walls, installation of improved water taps, and installation of a heat recovery unit in the ventilation system. We follow the buildings' life cycles and calculate the primary energy use during the production, retrofitting, operation and end-of-life phases, and the energy reduction achieved by the measures. The results show that the measures give significantly greater life cycle primary energy savings when using resistance heating than when using district heating. However, a resistance heated building with the efficiency measures still has greater life cycle primary energy use than a district heated building without the measures. Ventilation heat recovery is the most effective measure when using resistance heating while improved windows and doors is the most effective when using district heating. This study shows the importance of considering the interactions between individual measures and the type of heat supply system when selecting energy efficiency measures.

The Army is required by law (Energy Policy Act of 2005 [EPACT] 2005, U.S. Energy Independence and Security Act of 2007 [EISA] 2007) to eliminate fossil fuel use in new and renovated facilities by 2030 and to reduce overall facility energy usage by 30% by 2015. Army policy is to achieve 25 net zero energy installations by 2025 and to achieve net zero energy (NZE) status for all installations by 2058. Achieving NZE will only be possible if an optimum mix of demand reduction and renewable sources are put in place at a community (installation) or building cluster scale. The Army runs what are essentially small campuses, or clusters of buildings on its installations. The Department of Energy (DOE) is focused on the national grid scale or on individual buildings, while the commercial focus is on retrofits to individual buildings There is a lack of tools and case studies that address dynamics of energy systems at the community scale. The Army’s future building energy requirements are a mixture of ultra-low and high energy intensity facilities. Achieving net zero energy economically in these clusters of buildings will require a seamless blend of energy conservation in individual buildings, combined with building systems automation, utility management and control, and power delivery systems with the capability to integrate onsite power generation (including from renewable energy sources) and energy storage. When buildings are handled individually each building is optimized for energy efficiency to the economic energy efficiency optimum and then renewables are added until the building is net zero. This process works for buildings with a low energy intensity process for its mission, such as barracks and administrative buildings. When the mission of the building requires high energy intensity such as in a dining facility, data center, etc., this optimization process either will not end up with a net zero energy building, or large amounts of renewables will be added resulting in the overall technical solution that is not cost effective. But when buildings are clustered together, after each building is designed to its economic energy efficient option, the building cluster is also energy optimized taking advantages of the diversification between energy intensities, scheduling, and waste energy streams utilization. The optimized cluster will minimize the amount of renewables needed to make the building cluster net zero. This paper describes this process and demonstrates it using as an example a cluster of buildings a Brigade Combat Team Complex at Fort Bliss, TX.