Systems Efficiency: A New Paradigm for Building Performance

Systems Efficiency: A New Paradigm for Building Performance

This piece was originally published in the June 2018 issue of electroindustry.

Mikelann Scerbo, Strategic Initiatives Associate, and Laura Van Wie McGrory, Vice President, Strategic Initiatives, Alliance to Save Energy, Susan Rochford, Vice President, Energy Efficiency, Sustainability & Public Policy, Legrand Jeffrey Harris, Consultant

Despite decades of progress in equipment efficiency, total energy use by commercial buildings in the United States continues to rise.

Driving ever greater advances in building energy efficiency—along with improvements in overall building performance and resilience—will depend on the market’s ability to embrace integrated, system-level solutions. Traditional approaches to energy efficiency have focused on individual equipment or envelope components, or on the whole building. Often underemphasized is the potential for better performance of building systems.

Challenging Conventional Wisdom

From 2015 to 2017, the Alliance to Save Energy led the Systems Efficiency Initiative (SEI), with NEMA as a key participant. The SEI provided a forum for exploring the energy savings potential of a systems approach and developing strategies to move the market in this direction. The scope of the initiative included individual building systems; and interactions between systems, other buildings, and the electrical grid.

The SEI report Going Beyond Zero: A Systems Efficiency Blueprint for Building Energy Optimization and Resilience offers a broad set of recommended actions to gain systems-level energy savings.[1]

SEI defines building system energy efficiency as the ratio of (a) the services or functions provided by a building system to (b) the amount of energy that system consumes directly, taking into account the thermal load imposed on other building systems. In a systems-efficient building, multiple building systems are designed, installed, and operated to optimize performance collectively to provide a high level of service or functionality for a given level of energy use.

Several factors make a systems approach increasingly critical. Building energy use continues to rise, despite declines in commercial building energy intensity (energy/floor area), due in part to the rapid increase in miscellaneous electrical loads (MELs) and their associated additional cooling demand. By 2035, the U.S. Department of Energy (DOE) predicts that miscellaneous end uses will use as much energy as all other building end uses combined.[2]

Future improvements in equipment efficiency will continue to be essential in slowing load growth but won’t be enough to halt it. As building components start to approach technical and economic limits for further efficiency gains, a systems approach will become increasingly important for opening new paths to optimize energy use.

A systems approach also can achieve significant non-energy benefits: reduced carbon emissions, improved grid reliability and building operating resilience, water savings, extended equipment life, and increased occupant comfort and productivity. The quantifiable non-energy cost benefits of systems efficiency have been estimated to range from 25 to 50 percent of the total benefits of energy efficiency.[3]

Across the many types of buildings, systems, and system-efficiency approaches, a common thread is the central role of sensors and controls. System-level efficiency is driven by the collection, monitoring, and communication of data from the emerging Internet of Things, cloud-based analytic platforms that manage and interpret data along with artificial intelligence to monitor and predict system operations and prescribe automated responses. This integral role of sensors and controls calls for a higher level of attention to issues of data privacy and cybersecurity.

Unpacking the Layers

Building systems strategies can reduce energy consumption through improved connectivity and controls, thermal exchanges, and multisystem integration. These strategies are most easily applied in new construction but also can be implemented in existing buildings during renovations or systems upgrades. The following examples unpack the layers of systems efficiency solutions, ranging from individual building systems to multibuilding opportunities.

Layer One: Building Systems Efficiency

Example: Lighting Efficiency

The traditional view of systems efficiency focuses on individual building systems, like lighting or HVAC. This level of focus continues to offer significant potential for energy savings. Energy used for lighting, for example, represents about 10 percent of commercial building electricity use.[4] Although energy-efficient lighting components are critical for reducing energy use, effective lighting and daylighting system design and controls offer significant additional energy savings.[5]

A 2013 study of a high-performance office building in New York City documented lighting energy savings of 56 percent from daylight dimming controls and setpoint tuning in the daylighted spaces, compared to a code-compliant (ASHRAE 90.1-2001) building with scheduled on/off controls.[6] Furthermore, a 2015 study in two General Services Administration (GSA) federal office buildings with updated LED lighting and controls documented measured savings of 32 to 33 percent of lighting energy.[7]

Conversely, poorly controlled daylight strategies can increase unwanted solar heat gain that adds to a building’s cooling load. This underscores the importance of appropriate glazing choices and shading devices, which balance the energy benefits of daylighting as a key component of a systems approach.

In the TELUS Garden Office Tower in Vancouver, British Columbia (Figure 1),[8] automated interior solar shades and light shelves are controlled with a network that communicates with the building management system for daylight harvesting and glare control. The shades adjust throughout the day according to seasonal schedules to block solar heat gain in the summer and exploit it in the winter, reducing the building’s demand for cooling, heating, and electric light while enhancing exterior views.

Figure 1. Automated interior solar shades and light shelves in the TELUS Garden Office Tower in Vancouver adjust throughout the day. Photo courtesy of Canada Green Building Council [9]

Layer Two: Systems-Efficient Buildings

Example: Cross-System Interactions

The next level of systems efficiency involves the integration and optimization of multiple building systems. Integrated controls, often combined with a building management system (BMS), better manage energy consumption. They increasingly function on a distributed rather than a centralized basis. For example, lighting is zoned to respond to the needs of occupants in the immediate area, rather than to a central control module.

Advanced lighting control systems also can provide real-time information on energy use and illumination levels to facilitate energy management. For example, some occupancy sensors control both lights and receptacles for plug-in MELs. Open-system protocols can facilitate the integration of MEL local controls with the BMS, using shared occupancy sensors to turn off or put in “sleep” mode computers, printers, lighting, and zoned HVAC.

The coordination among building systems can be supported through integrated project delivery (IPD). IPD captures additional performance benefits through collaboration among design and construction teams to consider interactions between systems.

Example: DC Power

The incorporation of direct current (DC) power distribution creates additional opportunities for systems-efficient buildings by avoiding conversion losses when going from DC to AC (alternating current) to DC. A growing number of appliances and equipment in commercial buildings are either native DC-powered or use DC power for internal components such as sensors, controls, and variable speed motors.

Estimates of energy savings from DC distribution vary. A recent literature review shows model-estimated energy savings ranging between two and 14 percent, while measured savings range from two to eight percent.[10] The variation in savings depends on building types and end uses served by DC distribution, the presence of battery storage and on-site photovoltaic (PV) power, DC voltage levels and their associated line losses, and the overall power system configuration.

On-site power from a PV array (Figure 2), fuel cell, or battery storage increases savings opportunities and enhances the resiliency of a building as an emergency-ready power source. The National Renewable Energy Laboratory (NREL) is developing a DOE-sponsored tool to estimate the costs and benefits of DC power for specific building applications.[11]

Figure 2. As depicted in this artist’s rendering of the penthouse of the renovated American Geophysical Union headquarters in Washington, D.C., the direct current electrified grid will enable most devices in the building to use solar power from the PV installation on the roof without conversion losses. Image courtesy of the American Geophysical Union[12]

Layer Three: Neighborhood Efficiency

Example: A Shared Energy System

Looking beyond an individual building, a systems approach can encourage the integration of multiple buildings into a shared energy system. District energy systems (DES) for heating and cooling can reduce heating and cooling energy in urban buildings by as much as 30 to 50 percent by balancing thermal loads among multiple buildings and operating larger turbines or boilers at an optimal level, often as part of a combined heat and power (CHP) system.[13]

For facilities with simultaneous heating and cooling needs, the load diversity among buildings may provide a free resource when the circulating loop is combined with building-level heat pumps and, in some cases, is supplemented by seasonal thermal storage using shared geothermal wells or nearby bodies of water.

Layer Four: Energy Ecosystem

Example: Buildings-to-Grid Integration

The increasing attention on buildings-to-grid (B2G) integration reflects the growing recognition of the efficiency opportunities and other benefits offered by this level of systems approach. The DOE vision of a fully integrated, transaction-based B2G ecosystem would optimize systems efficiencies, reliability, and cost-effectiveness at both the building and grid scale, while paving the way for more effective integration of renewable resources and electric vehicles.[14]

The growth in distributed generation combined with demand response, microgrids, advances in battery storage, sensing and controls, wireless connectivity, and big data analytics is making it even easier for building systems to act as distributed energy assets to strengthen the utility grid’s efficiency and reliability.

Five Steps to Systems Efficiency

NEMA advances systems efficiency at many levels, including advocacy for grid modernization and ongoing work to develop Standards that define lighting systems and provide performance ratings.

A combination of research, development, and demonstration (RD&D); pilot projects; public leadership policies; incentives; and regulations is required to demonstrate the benefits of systems efficiency, incentivize a systems approach in consumer behavior and design choices, and ultimately improve energy savings and energy productivity.

  1. RD&D. Lawrence Berkeley National Laboratory’s Beyond Widgets project is an example of RD&D that has resulted in the development and validation of common packages of energy conservation measures for lighting or HVAC systems in smaller buildings.[15] At the state level, New York pioneered the application of packaged CHP solutions to building-scale projects as well as larger, industrial installations. The private sector is also taking steps to advance systems solutions: the Air Conditioning, Heating, and Refrigeration Institute and ASHRAE are developing new approaches to measuring and rating the performance of HVAC systems.[16]
  2. Pilot projects. Pilot projects in the systems arena have ranged from demonstrations of advanced lighting and daylighting controls to the new CHP system serving a district energy loop in the nation’s capital.[17] A field demonstration of the DC-powered Sustainable Colorado office building[18] shows how a systems approach to intelligent buildings allows the merging of power, data, and control into a single unified platform.
  3. Leadership by the public sector. Leadership can demonstrate the feasibility of system concepts and open new markets that reduce risk and encourage innovation. The GSA has helped lead the way in applying integrated design concepts to new construction and major renovation,[19] emphasizing collaboration across many disciplines (architects, engineers, sustainability experts, and facility operators) to introduce a systems perspective.
  4. Building energy rating and recognition programs can familiarize designers and builders with systems solutions. The Leadership in Energy and Environmental Design (LEED) rating system encourages an integrated design process and credits on-site renewable energy and CHP.
  5. Building codes can further incentivize a systems approach. For example, most model codes allow tradeoffs in lighting power density among spaces in the building to achieve an overall building average. These tradeoffs, however, do not provide full credit for lighting controls that contribute to overall system performance. A promising new direction is outcome-based regulation of building energy performance.[20] In particular, NEMA LSD 62-2012 Systems Approach for Lighting addresses “energy savings by shifting the regulatory focus from appliance standards to lighting systems standards as incorporated into building energy code.”[21]

Optimizing systems efficiency in new and existing buildings will require addressing system performance and multisystem interactions throughout design, construction, and building operation. Policymakers, designers, and building owners need to prioritize systems efficiency, with controls and sensors as critical enablers, to achieve the next level of efficiency in buildings and enhance the energy reliability and resilience of buildings.
















[16] Richard Lord, “Future HVAC Efficiency Improvements,” 2013,






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