Zero Energy Buildings

Zero energy buildings, or net zero buildings, aim to equalize energy production and consumption by combining energy efficient design and maintenance practices with on-site renewable energy generation.
Tom Chance, Flickr

The Definition of Zero Energy

According to the U.S. Department of Energy (DOE), a zero energy building (ZEB) is defined as an “energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy.”

How Do Zero Energy Buildings Work?

Zero energy buildings tackle the problems of conventional buildings head on, sealing up structural and technological fissures with energy efficiency strategies and meeting remaining demand with on-site renewable generation. Net zero energy is only possible if both components are configured into an integrative system that is continually evaluated and maintained with energy analysis tools.

Energy Efficiency Strategies

The National Institute of Building Sciences’ Whole Building Design Guide (WBDG) has identified a number of efficiency measures common to ZEB design, construction and maintenance, including:

  • High-performance envelopes
  • Air barrier systems
  • Daylighting
  • Sun control and shading devices
  • Careful selection of windows and glazing
  • Passive solar heating
  • Natural ventilation
  • Water conservation

Energy efficient equipment and systems, which go hand-in-hand with the strategies listed above, are also crucial to achieving net-zero energy levels. The WBDG highlights a few, among them:

  • Energy efficient lighting
  • Electric lighting controls
  • High-performance HVAC
  • Geothermal heat pumps

ENERGY STAR, a U.S. Environmental Protection Agency (EPA) program, has spent nearly 25 years promoting and certifying energy efficient products. The ENERGY STAR website’s product catalog is an excellent resource for project teams looking to meet a zero energy performance target.

On-site Renewables

While energy efficiency reduces usage significantly, on-site renewable energy systems are needed to produce energy that offsets consumption levels and achieves truly “net-zero” energy performance. ZEB projects must choose sources that suit their location, capacity and anticipated needs. The following have been noted by the WBDG for their practicality and reoccurrence:

  • Photovoltaics (PV)
  • Solar water heating
  • Wind turbines
  • Biomass (on-site thermal)

Although on-site renewable energy is essential to ZEB functionality, most are still connected to conventional grids on some level. Enforcers of ZEB standards identify certain off-site sources as acceptable. The U.S. government, for example, allows emerging ZEBs to outsource generation to solar, wind and other renewable resources. 

Energy Monitoring and Analysis Tools

Measuring, tracking and collating the energy performance data of ZEBs is a task as necessary as it is demanding. Only through continuous, thorough data collection and analysis can ZEB developers and certification programs verify net zero capabilities. Such calculations also contribute to the ever-growing online cache of data that current and future ZEB project teams can consult when needed, helping them keep pace with the field’s fast-evolving demands.

The metrics needed to calculate energy performance are typically distributed across multiple sources, including utility bills, energy dashboards and software-engineered outputs and spreadsheets. Systematic monitoring technology is used to generate real-time feedback and diagnostics, a tool the NBI’s latest ZNE report cited as key to evaluated projects’ operations and occupant engagement strategies.

The report also found plug load reduction to be a growing concern of ZEB projects. Plug loads, as defined by the U.S. General Services Administration (GSA), refer to the “energy used by equipment that is plugged into an outlet.” The GSA estimates that plug loads may account for up to 50 percent of total energy consumption in high efficiency buildings. While energy efficient appliances may have the biggest role to play in plug load reduction, IT departments can also implement software that either automates system shut-offs or prompts occupants to turn off plugged equipment.

The History of Zero Energy

In 2012, the Scientific American published a writeup on the potential of zero energy buildings when the phenomenon was in its earliest stages. The article drew on research compiled by the New Buildings Institute (NBI), which confirmed that at least 21 commercial buildings located in the U.S. met net-zero energy standards. Another 39 buildings that nearly qualified but lacked the requisite amount of on-site renewables were classified as “emerging.”

Two years later, the NBI issued an update confirming that the verified and emerging building count had more than doubled, increasing from 60 to 160. What had been a distant ambition just a few years prior had become not only an actionable reality, but a substantiated success. As conversation surrounding the concept mounted, so did the demand for a common definition -- an issue the DOE settled in 2015, with a report titled “A Common Definition for Zero Energy Buildings.”

The purpose and true essence of ZEBs lies in their goal of reaching “net-zero,” or the point when the amount of energy a building produces on-site equals the amount of energy it consumes. Known by many other names -- among them net-zero energy buildings and net energy buildings -- ZEBs are a former pipe dream of eco-enthusiasts that has only recently become a reality in the building sector.

The Problems with Conventional Buildings

As record-breaking temperature increases continue to precipitate a steady escalation in electricity consumption, energy leakage has become a matter of increasing concern. The U.S. Energy Information Association (EIA) found, in 2015, that 40 percent of national energy consumption traced back to residential and commercial buildings. Generations of uneven building codes, uneconomical equipment and unsustainable design schemes, in addition to neglect of operations and maintenance (O&M) and evaluation, have created literal gaps in the infrastructure of American buildings.

Through the gaps -- which can be found in the building envelope, HVAC systems, and other various design components -- energy escapes on a regular basis, contributing to a simultaneous pileup of wasted energy and corresponding costs. Many of the defects at fault can be easily fixed and even prevented at the design stage, so long as project teams understand how to implement effective energy-saving strategies.

The Benefits of Zero Energy Buildings

Cost Reduction

ZEBs are held accountable to their claim of net-zero energy levels with energy analysis tools, such as performance software, rigorous documentation apparatuses and life cycle assessments. Essential to the utility of these tools is a running tally of energy costs, which serves as a metric by which ZEB certifiers grade performance.

Such cost analyses at the same time reveal the financial benefits of operating ZEBs -- a far cry from the losses associated with conventional buildings. A financial study prepared by the International Living Future Institute found that, for the ZEBs assessed, the return on investment (ROI) reached an average of 30 percent. Energy efficiency measures alone ranged produced ROIs of five to 12 percent.

Environmentally Friendly

Designed with the explicit purpose of minimizing environmental impact, zero energy buildings combine an assortment of eco-friendly principles and practices that target and eliminate sources of potential energy wastage.

Integrative Design

The concept of integration, or the unification of individual elements into a single whole, has become a pillar of sustainability and capacity-building for a broad span of industries and disciplines. Green building has absorbed the idea with particular enthusiasm, as evidenced with certification systems like LEED and the WELL Building Standard.

Zero energy buildings represent integrative design at its peak, coordinating the design and operation of building components that, in a typical conventional building, tend to function as separate entities. What ensues is a synchronization of parts on a theoretical level -- between decision-makers, planners and other stakeholders during the design phase -- and a practical level, between building systems and technologies throughout construction and thereafter.

The integrative approach also extends beyond the design apparatus. In August 2016, the Rocky Mountain Institute devised an integrative business model that packages the premise of zero energy building districts with informative, schematic modules designed to appeal to relevant stakeholders (namely, developers and tenants). The brief details financial and managerial strategies, as well as potential barriers and corresponding solutions, that can be addressed from a business perspective.

Education and Awareness

ZEBs encourage project teams, distributors and occupants to take part in the pursuit of net zero energy targets. Project teams, when confronted with the holistic demands of designing ZEBs, must expand and apply their sustainability expertise not only during the blueprinting phase, but throughout their projects’ life cycles as well. Increased and continual engagement is also required of building occupants, who can minimize plug loads and overall consumption by engaging in energy efficient practices.

The International Living Future Institute, which administers the Net Zero Energy Building Certification program, maintains an education arm that organizes events, offers online courses and compiles a cache of research reports -- all easily accessible and fit for public consumption. The certification program cites public education as one of its main applications, requiring projects to regularly upload verified and updated data to its Case Study Database.

ZEB projects thus also contribute to sustainability education on an individual basis. Some offer in-person and virtual tours that allow audiences to interact with a building’s energy efficient components. Singapore’s BCA Academy houses a ZEB, claimed to be the country’s greenest, that the public can peruse online. Legend Homes uses links and PDF files to construct its own variation of a virtual tour of the design firm’s zero energy homes, an approach similar to the U.S. Department of Energy (DOE)’s own regionally indexed tour module.

The Challenges of Zero Energy Buildings

Due to the relative recency of the zero energy building phenomenon, the relevant data currently available is too deficient and prone to clerical error to establish empirical and statistical benchmarks for project teams to follow. According to the NBI’s 2014 update on ZEBs, limitations specific to individual building sites also vary widely, further obstructing the development of a common frame of reference for the time being.

Cost estimates, for the same reasons, are also dubious at this time. An International Living Building Institute cost comparison report pointed out that intersecting billings make it difficult for project teams to cordon off the financials needed to reach net zero from the rest of the budget. Net zero skeptics have questioned whether the sustainability and profitability of successful ZEB case studies can apply to more ambitious and affordable projects.

The Growing Demand for Zero Energy

In 2014, the NBI reported that ZEBs burned through a mere quarter of the average commercial building’s energy use. Also noted was the fact that large-scale ZEB projects, for all their additional design and constructional challenges, are gaining in popularity and didn’t skew consumption calculations.

The surge in ZEB construction is largely owed to the generous contributions and support of the public sector. Schools and government agencies commission two thirds of ZEB projects, though the NBI revealed that private sector engagement is also on the rise at 26 percent ownership.

Data gathered recently shows a more vested interest in building efficiency measures across the board. The 2016 Energy Efficiency Indicator (EEI) Survey, for instance, quantified the influence of energy efficiency on the building portfolios of reigning decision-makers. Nearly three quarters of respondents confirmed plans to increase investment in energy efficiency within the year -- up a full 30 percent from the survey’s 2013 edition. Some 85 percent also agreed that their organizations were spotlighting energy efficiency more now than the preceding year, a 17 percent increase from 2013.

The inclusion of ZEBs in U.S. federal legislature serves as further testament to their legitimacy and success. The Obama Administration’s Executive Order 13514, which dates back to 2009, set a net-zero target for all new construction of federal buildings that would be mandatory from 2020 onwards. The order was later revoked and absorbed into the newly minted Executive Order 13693, which put forth a broader and even more aggressive approach to integrating zero energy performance targets into federal building design.

Net Zero Energy Building Certification

So far, the International Living Building Institute’s Net Zero Energy Building Certification (NZEB) program is the only of its kind worldwide. Operated alongside the Institute’s Living Building and Living Product Challenges, the program uses a system of checks and balances to verify, support and recognize building projects’ achievement of net-zero energy performance.

The following principles and applications are emphasized in the program’s requirements:

●      Verification: Buildings must submit themselves to an intermittent third party audit of performance data, in order to ensure that net-zero standards are being upheld.

●      Public Education: A regularly updated and easily navigable Case Study Database both tracks ZEB developments and provides an invaluable source of evaluations for ZEB present and future ZEB project teams.

●      Recognition: Incentives are doled out to projects that demonstrate adaptability, creativity and resolve.

Projects are held accountable to their commitments through a rigorous documentation scheme, which draws on imperatives from the Living Building Challenge to help teams construct and follow a detailed course of action.

Zero Energy Homes

In 2013, the U.S. Department of Energy (DOE) took its successful Builders Challenge program -- which helped 14,000 homes achieve energy efficiency -- to the next level by launching the Zero Energy Ready Home (ZERH). The initiative’s purpose is twofold, spotlighting builders who innovate ZERH designs while promoting a comprehensive zero energy schema. By 2050, the DOE estimates ZERH proliferation to have a nationwide impact of:

●       $250 billion USD in utility bill savings

●       2.3 million job years created

●       80 million barrels of imported oil saved each year

What Are Prefab Energy Homes?

Prefab companies, too, are integrating net zero energy targets into their products, capitalizing on what is poised to be an increasingly economical and marketable design concept. Prefab zero energy homes combine the speed, convenience and structural integrity of prefabrication construction with the quality guarantees of zero energy standards. The National Renewable Energy Laboratory recommends maximized use of offsite prefabrication as a means of cost control.

In September 2015 Deltec Homes announced the Renew Collection, a line of panelized homes that shared a prefab zero energy design. The Zero Energy Project reported that the collection is built to accommodate on-site solar technology, as well as diversified enough to suit buyers of different price ranges.

The David & Lucile Packard Foundation Headquarters: A Zero Energy Building Case Study

Certified LEED Platinum in 2012 and awarded Net Zero Energy Building certification in 2013, the David & Lucile Packard Foundation Headquarters is the world’s largest Net Zero Energy Certified building to date. Located in Los Altos, California, the building fuses energy-efficient structures, materials and technology to form a work environment that meets both environmental and occupational standards.

In the spirit of transparency and public awareness, the Foundation has made public its master plan for maintaining net zero energy levels, which includes further strategies for minimizing environmental impact. Those strategies target the following areas:

  • Net Zero Energy: Hundreds of roof-mounted solar panels, chilled beam technology and well-harnessed daylight aim to offset the headquarters’ energy needs completely.
  • Water Conservation: Rainwater harvesting and collection systems, in addition to sparse, eco-friendly irrigation, are designed to reduce water consumption by 40 percent.
  • Materials and Waste: Part of an effort to mitigate the pileup and adverse effects of construction waste, 95 percent of construction materials originated from pre-existing buildings.
  • Ecosystem Impact: To avoid encroaching on the surrounding ecosystem, the building’s landscape is comprised predominantly of plants native to California.
  • Work Environment: The building ventilates outside air alone, safeguarding occupants from the indoor air pollution hazards of conventional HVAC systems.

The International Living Building Institute built an online profile of the Foundation’s headquarters that dives deeper into its net zero energy design, outlining with plenty of quantitative detail its energy monitoring methods, generation operations and eco-friendly aesthetics -- all proportioned to service over 50,000 square feet of space.

Zero Energy Building Districts

The integrative aspect of zero energy modeling makes it an ideal fit for community- and district-wide projects, which are on track for becoming the next frontier of ZEB design and construction. In 2014, the NBI identified 17 emerging district-scale projects with zero energy performance targets. With on-site renewable generation facilities that supply multiple buildings, zero energy building districts have the potential to be even more cost-effective and energy efficient than their singular counterparts.

Now that new technology and obliging markets have made zero energy building districts a fully actionable reality, numerous authorities on green building and design are encouraging stakeholders and policymakers to invest in their construction.

The Rocky Mountain Institute’s integrative business model for net zero energy districts, for example, asserts that “district-scale developments are uniquely positioned to be a major driver of the next generation of high-performance buildings.” The International Living Building Institute is also vouching for district systems, pointing out that community-scaled projects allow one building’s wasted energy to become another’s generation source.

At present, most municipal building policies lack the legal and logistical frameworks needed to bring zero energy districts to fruition in the public sector. The New Buildings Institute encourages urban planning departments at the local level and beyond to create and catalyze opportunities for ZEB district construction. Doing so, they claim, will lay the groundwork for areas in which zero energy achievement might otherwise be considered impractical.

LEED and Zero Energy

Thanks to mutually held energy and environmental standards, LEED certification and zero energy building projects go hand-in-hand. In fact, in 2014 half the commercial buildings designated by the NBI as current or emerging zero energy achievers were Gold- or Platinum-certified.

Representatives of the USGBC Platinum-level company DPC Construction have called LEED the “logical baseline for net-zero energy strategies” — an estimation that the USGBC has confirmed to be true in its “Net Zero Energy Buildings, the Future is Now” continuing education course. LEED-certified zero energy building projects are cataloged and available for viewing on the Green Building Information Gateway (GBIG), where building professionals can also investigate their corresponding sustainability strategies.

More on Zero Energy Buildings

For more information and source material on zero energy buildings, check out the International Living Future Institute’s education module. A ZEB event may even be coming to a neighborhood near you.

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