by Linnean Solutions — It has long been known that buildings account for the consumption of more energy than any other sector in the United States. Any attempt to reduce that usage to zero has been seen as a drastic, unachievable measure. However, with advances in technology and spreading awareness of the threats posed by climate change, more buildings are being designed to use net zero energy, a trend that is likely to increase steadily as time goes on. The U.S. government is helping to lead this shift, mandating that all federal buildings reduce non-renewable energy consumption to zero by 2030. Facilities management plays a critical role in achieving net zero, improving energy efficiency, and reducing the overall building energy use intensity.
What Does “Net Zero” Mean?
There are a multitude of definitions for a building designated as “net zero energy.” The most widely accepted meaning is a building that produces as much energy as it consumes on an annual basis. While this is a simple enough concept to grasp, confusions arise because “net zero energy” is often mistakenly interchanged with the term ‘net zero emissions”.
As defined by the U.S. Department of Energy, a building that has “net zero emissions” produces at least as much emissions-free renewable energy as it uses from emission-producing energy sources annually. Also referred to as “carbon neutral” or “net zero carbon”, such a building does not contribute to global warming. The energy that the building uses is produced by on-site renewable sources such as solar, wind, and biofuels or it is offset using Renewable Energy Certificates or through energy districts. However, some organizations’ definitions are much stricter than that of the U.S. DOE. The Living Building Challenge, for example, does not allow buildings certified as “net zero” to source any energy off-site; in order to be recognized as net zero, all energy consumed must be renewably produced on-site. Other definitions seek to include the embodied energy and carbon produced during construction of a building in its net zero calculations.
The crucial difference between net zero energy and net zero emissions is that under the latter, no net greenhouse gases are produced and thus there is no contribution to climate change. Under the most common definition, a building could operate using “net zero energy”, yet release emissions through the burning of fossil fuels on-site, for example. Under any definition, “Carbon neutral” or “net zero emissions” is a more difficult standard to achieve than “net zero energy”.
For the purposes of this article, net zero will refer to “net zero emissions” as defined by the U.S. DOE, described above.
Getting to Net Zero: Reducing Energy Use Intensity
Generally, there are three components to attaining and maintaining net zero usage: energy efficiency, on-site renewable production, and renewable energy purchased from the grid. Without taking smart steps toward efficiency and conservation of energy, it will be difficult or impossible for a building to achieve and maintain net zero and it is here that facilities manager can play the largest role.
Efficiency is perhaps the highest priority and most cost effective measure for projects seeking to be net zero. The first step for a facilities manager is to understand how their building uses energy and what its current operational and occupant requirements are. The second step is to evaluate how efficiently those needs are currently being met and if energy is being casually wasted. The third step is then to evaluate options, update, and improve with the goal of reducing the energy use intensity (EUI).
Here are some areas that can commonly be improved upon to increase efficiency and reduce EUI:
- Load reduction:
- Plug load management — use schedule-controlled power strips and outlets and low plug load equipment
- Install occupancy and dimming ballast sensors for lighting
- Lower domestic hot water temperatures
- Use software and dashboards to monitor and track energy consumption
- Prompt behavioral change – engage occupants through campaigns, signage, email reminders, etc.
- Passive strategies:
- Install shading devices — permanent overhangs on south facing windows and shades on east and west facing windows are especially effective
- Maximize opportunities to daylight spaces
- Explore possibilities for natural ventilation
- Maximize envelope performance to reduce HVAC system demands
- Efficient systems:
- Ensure that systems such as lighting and HVAC remain optimally sized
- Use the most efficient equipment and appliances
- Use automated night setbacks to turn down heating and lighting
- Energy recovery
- Evaluate the possibility of using heat exchangers and air recirculators
Once such steps have been taken towards operating more efficiently and lowering the EUI of a building, it is critical that performance continue to be reassessed and improved upon wherever possible. Operations should be optimized and a team should be formed to meet regularly to discuss possible further improvements.
A number of tools exist to aid facility managers and owners in the pursuit of becoming more energy efficient. The EPA’s no-cost EnergyStar Portfolio Manager can be a particularly useful tool for tracking and reducing a building’s EUI and general energy use. Other useful resources include the Sustainable Facilities Tool and the Whole Building Design Guide. More detailed guidelines for EUI reduction are published by ASHRAE and can be found here: Advanced Energy Design Guide.
Phipps Conservatory Center for Sustainable Landscapes
The Phipps Conservatory in Pittsburg, Pennsylvania has recently completed an addition that is on the forefront of sustainable design and operations. Certified in 2014 by the Living Building Challenge as a Net Zero Energy Building (LBC actually certifies buildings as “net zero emissions” but calls it “net zero energy”) and LEED Platinum certified, the Phipps Center for Sustainable Landscapes is a revolutionary model for energy efficiency.
The Phipps Center uses a variety of innovative techniques and cutting-edge technology to achieve net zero usage. One fundamental component of the building’s operations is its Building Management System (BMS). The Center’s BMS includes features such as Direct Digital Control to centralize monitoring, controls, and system feedbacks and an alert system that notifies occupants when it is best to open windows. Many systems are automated to conserve energy; meters and sensors provide current and historical operating information to inform managers and monitor overall EUI.
Passive strategies such as natural ventilation and daylighting are maximized throughout the Center and occupancy sensors are employed to reduce energy waste. Outside the Center, the landscape is low maintenance and requires no irrigation and sidewalk snow is melted using condensate from waste heat. Solar PVs and wind turbines renewably meet all of the Center’s energy demands.
While the Center maximizes its use of high performance equipment with some of the most advanced sustainable design practices and technologies, it would not have been able to achieve and maintain net zero emissions status without the use of an integrated design process that included the facilities operations team. Throughout the Center’s design and planning, needs were comprehensively evaluated and teams met regularly design and evaluate the building and the systems.
When pursuing net zero, the reduction of a building’s overall energy use, as reflected in EUI, and subsequent continual operational enhancements are vital. As such, it is important to keep a number of points in mind. First, as demonstrated by the Phipps Center, net zero can only be achieved through a whole building integrated design process and dedicated teamwork. Actions should be considered holistically rather than individually. Immediate, simple steps towards the maximization of energy efficiency should be undertaken prior to pursuing more involved measures. Second, constant reassessment and improvement of operations is important, along with encouraging energy mindfulness and engaging occupants. Third, tax incentives and energy grants should be pursued when making system modifications and technological enhancements. Finally, remember that while striving to achieve net zero, team collaboration and clear communication of design goals and maintenance processes are critical; a building’s systems and performance must be understood before they can be improved upon.