by Bob Graves and Charles “Russ” Russell

Feb. 20, 2010

As retired building official, I remember the many day-to-day challenges of the job. Now as a consultant to several cities and building industry professionals, I see these challenges becoming even more complex with each new code cycle. Green building measures are becoming more prevalent, and California leadership, both in government and industry, has been active in setting consumption energy limits for the future.

The term “Zero Net Energy” (ZNE) refers to the ultimate goal set forth for residential and commercial buildings: to generate the energy they use on a daily basis. By 2020, all newly constructed homes will have to meet this standard. With Bob Graves of Green Technology, I have co-written an article on ZNE and wanted to share it with you. I hope you find it informative. Please do send any feedback or questions. – Charles “Russ” Russell

California has been a leader in energy policy for decades and its next major initiative is no exception. As a result of energy efficiency standards initially implemented in the 1970s (and regularly upgraded since then), California’s per capita energy consumption is the lowest in the nation and has remained relatively flat while the rest of the U.S., taken collectively, has risen 40 percent. This has resulted in savings to residents of more than $56 billion.

The new news in California building is the zero net energy (ZNE) standard for residential and commercial construction. On an annualized basis, a zero net energy building consumes as much energy as it generates through a renewable energy system. The goal is to minimize energy use as much as technologically possible by cost-effective efficiency measures and then meet the building’s energy needs with onsite renewable energy generation.

The importance of ZNE buildings is evident by their inclusion in a number of high-level, policy planning documents dating back to the 2003 Energy Action Plan that established energy efficiency as the highest priority in the loading order for energy resources. The ZNE standard is the result of a concerted series of planning steps spanning the better part of a decade.

The California Energy Commission’s recently issued draft 2011 Integrated Energy Policy Report (IEPR) lays out strategies, plans and implementations related to the deployment of the ZNE standard. The Energy Commission, California Air Resources Board (ARB), and the California Public Utilities Commission (CPUC) have adopted the policy goal, consistent with existing statutory authority, to achieve zero net energy (ZNE) building standards by 2020 for residential buildings and 2030 for commercial buildings through the 2008 Energy Action Plan, 2007 IEPR, and the 2008 California Long-Term Energy Efficiency Strategic Plan. The CCEF (California Clean Energy Future) initiative and Governor Brown’s Clean Energy Jobs Plan also identify ZNE as a priority goal.

Flexibility for Achieving Energy Efficiency As outlined in the IEPR, California’s mandatory building efficiency standards “are fundamentally performance standards that establish an ‘energy budget’ for the entire building as an alternative to prescriptive requirements for individual components. This affords California builders, designers, and contractors the flexibility to achieve energy efficiency in buildings using a wide array of measures that fit their construction goals and meet the standards at the lowest cost.”

The report goes on to state, “the Building Standards are an important strategy for meeting the ZNE goal, as each subsequent standards update (done on a three-year cycle) will progressively raise the bar by requiring increased energy-saving features in building designs and equipment.” Through cost-effective efficiency requirements, the Energy Commission hopes to achieve a 20 to 30 percent energy savings for each triennial Building Standards update. As an initial step, the 2013 Building Standards will address high-efficacy building envelopes, lighting, and heating, cooling and water heating systems, and energy demand response management technologies. Before on-site power generation is required, energy consumption will be reduced by implementing all efficiency measures that have a lower cost than renewable technologies.

An Innovative Approach
The state is using an innovative approach of ramping up mandatory energy efficiency standards within its energy code (Title 24, Part 6), while encouraging local jurisdictions to use higher level “reach” voluntary standards (Tiers) available through the recently adopted California Green Building Standards Code (CALGreen). The 2010 CALGreen incorporates three levels of energy efficiency: a basic level fixed to the energy code as well as two options: Tier 1 at 15 percent increase above Title 24, and Tier 2 at 30 percent increase above Title 24 requirements.

Local jurisdictions have the ability to adopt and enforce local Tier 1 and Tier 2 ordinances (or reach codes) based on specific state guidelines and requiring approval from the Energy Commission and filing with the Building Standards Commission. Experiences from these local jurisdictions will provide valuable feedback to the progression of code adoptions for the balance of the state. In essence the state is taking advantage of the Tiers (reach codes) as a proving ground for future state energy code upgrades.

The Tier implementations also give the design and construction community, as well as local building departments, a glimpse into the future and allow for preparation as new code amendments are released. Definite marketplace benefits accrue as construction proceeds under these reach standards. As is the case with all new technologies, costs will decline not only for the technology itself but also for the construction process as a whole through gains in expertise in delivering them. The more mainstream green building construction becomes, the less it costs.

New Features
The current energy code is contained in the 2010 edition of the California Energy Code, and the 2013 Energy Code is under development (recently released for public comment). The 2013 Energy Code will reach 70 percent of the residential ZNE goal; the 2016 Energy Code 85 percent, and the 2019 Energy Code will meet the goal of ZNE. The state will also link CALGreen and the Energy Code so that both are on the same path traveling at the same speed while providing access to successively higher levels of energy efficiency through the Tiers for local jurisdictions to adopt.

Review of the proposed 2013 Energy Code shows new code features designed to pave the way to ZNE buildings. For example, the state introduced “Mandatory Requirements for Solar Ready Buildings” in Section 110.10. This new section sets the minimum requirements for size and location of the solar zone for a given type of occupancy. To support renewable energy, the California Energy Commission (CEC) has developed standards and tools for achieving high-performance rooftop photovoltaic (PV) systems. These standards and tools are designed to promote high efficiency solar energy system components, effective installation practices, and calculation and demonstration of expected system performance.

Another new feature is Section 120.8 “Building Commissioning” for energy related systems. Non-Residential building commissioning was introduced in the 2010 CALGreen Code in Section 5.410.2. Commissioning goes beyond building code verification and requires the use of documentation to inform the building owner that all goals established by the owner and the design team were accomplished and that the building performs per the design criteria.

Putting ZNE into Practice
How is ZNE achieved in actual practice? The specifics involved in designing a zero net energy building include extensive energy efficiency built into all parts of the residential occupancy, including lighting, appliances, insulation, building envelope, windows, doors, HVAC system, etc. Once the design team has complied with, or come as close as possible to, complying with the code requirements for light, ventilation, heating, cooling, and appliances, the house can be modeled on energy use, including electrical receptacle loads, using state approved software, to calculate the amount of renewable energy (photovoltaic, wind, geothermal, etc.) needed to achieve compliance. It’s important to note that building energy usage includes plug loads, since they are responsible for more than 50 percent of residential energy consumption.

The ongoing development of the ZNE standard and energy codes in California offers a glimpse into new territory for stakeholders. The path the state charts will surely provide signposts for similar efforts nationally and internationally. Already changes are in the offing, according to a Strategic Plan Progress Report from the CPUC: “when ZNE commercial ‘champions’ convened in 2011 to discuss and seek consensus on an updated ZNE definition that the CPUC, CEC and other building sector stakeholders all might utilize. The intent is to clarify ambiguities and suggest ways to recast ZNE goals in terms that are easy to understand and market to the building and property industries, while preserving ZNE policy principles and technical considerations.”

The resulting goal for ZNE building would be clarified to “all new residential construction in California will be zero net energy or equivalent to zero net energy by 2020” (and 2030 for commercial). Such a change would allow the standard to be applicable to all buildings, even those projects unable to generate a sufficient amount of on-site energy to achieve a ZNE status. Additionally, this modification to the definition will allow approximately 50 percent of existing buildings to be equivalent to ZNE with the achievement of aggressive energy upgrades and clean distributed generation. For example, under this scenario credits could be granted toward “equivalent” through purchase of renewable energy credits (RECs), averaging of multiple buildings on a campus or off-site renewables under the same ownership.

A Coordinated Action
The importance of coordinated action between codes and standards is perhaps best illustrated in a reference from the Zero Net Action Plan released by the CPUC in September 2010. The Plan, developed over an 11-month period, represents the collaboration of more than 150 stakeholders in non-residential building, architecture, finance, clean energy, technology, and various state agencies.

“Energy codes are a key policy strategy included in the Strategic Plan to reach ZNE buildings,” the plan says. “To achieve 100 percent zero net energy new construction buildings by 2030, building energy codes need to be a driving policy instrument and ultimately the mechanism by which zero net energy is broadly achieved. No incentive or market-based program can achieve the market penetration routinely achieved by codes.”

Bob Graves is editor at large for Green Technology magazine Charles “Russ” Russell is vice president of VCA Green