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The NIST Net-Zero Energy Residential Test Facility (NZERTF) is a highly instrumented, highly configurable, single-family, net-zero energy house occupied by a virtual family of four. A detailed transient model of the NZERTF and the accompanying mechanical equipment was created using information available before construction; the model incorporated building geometric details and construction material properties, as well as manufacturers’ specifications for HVAC, water heating, solar PV and other equipment. This model represents the typical design paradigm, where actual building performance and detailed equipment operation are not known. This original model underpredicted the measured annual energy consumption by 13.8 %. The measured data were used to understand and correct the sources of error at the component level; modifications to the HVAC system, interior thermal capacitance, and domestic hot water system improved the energy consumption prediction to within 1.6 % of measured data. The differences between the original and modified models are useful for understanding the sources, magnitudes, and possible corrections to errors in energy models for high-efficiency residences. The modified model will be used in future studies of alternative energy system configurations and control strategies, contributing to cost-effective and optimum design of net-zero energy houses in America.

Premise plumbing systems constitute an essential component of the built environment by providing immediate access to clean, potable water and a safe, reliable means of removing wastewater from homes, businesses and other institutions. Plumbing systems evolved extensively throughout the 20 th century beginning with efforts in the 1920s to develop the technical understanding needed to support system design and regulation, much of which was initiated by then Secretary of Commerce Herbert Hoover to address a range of health and performance issues. Plumbing systems continue to evolve in response to current concerns about cost, water availability, environmental impacts and safety.A series of policy actions including the Safe Drinking Water Act of 1974, the Energy Security Act of 1980 and the Energy Policy Act of 1992 sought to improve water quality, water use efficiency, and energy efficiency. These changes led to notable achievements including the reduction of lead in plumbing products and the introduction of low-flow fixtures. For example, a typical single-family, detached home today uses 22 % less water for indoor purposes than it did two decades ago (DeOreo, et al., 2016). As a result, the flow rates within the piping networks and the corresponding residence times can be significantly different than those assumed under current design methods. Consequently, the assumptions surrounding the effectiveness of water treatment practices are not necessarily applicable, leading to the potential for decreased water quality. These and other realities have led to a situation in which plumbing systems are being designed, installed and operated in vastly different ways from what is supported by the technical data and understanding embodied in current codes, standards and practice.Plumbing design approaches, codes and standards have not kept pace with these changes, in large part because of the existence of significant technical knowledge gaps. Research is needed to address these gaps in support of water efficiency and water quality goals to ensure the effectiveness of these systems today and in the future. This report documents specific research needs to advance plumbing system design, operation and maintenance, as well as the standards, codes and guidelines that apply to these systems. The primary concerns that motivated this effort to identify premise plumbing research needs are water quality, water efficiency, and energy efficiency. Water quality is one of the biggest concerns as it directly affects the health and safety of building occupants, and is becoming an increasingly complex challenge. Water quality concerns fall into three main categories: metallic, chemical, and biological. The need for water efficiency is expected to become more pressing as a result of population growth, climate change and infrastructure challenges. The availability of water is largely a regional issue, and there are many areas around the U.S. and throughout the world that are subject to recurring water shortages, even under non-drought conditions....