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22 / BUILDING DIALOGUE / November 2019 Let’s Talk Net Zero: Preparing for Evolving Code A SHRAE and IECC are headed toward creating net-zero energy standards for commercial buildings by 2030. California will have zero net energy building codes in place by 2030. It will not be too long before other states and cities adopt these standards as code. Boulder (ClimateMobilizationActionPlan) andDenver (80x50 Climate Action Plan) already have set goals that all new buildings achieve net zero energy by 2031 and 2035, respectively. If you are considering a net-zero project, you will want to be aware of the various definitions of net zero energy and howprojects should go about achieving it. • What is a net-zero energy building? There are many definitions of net-zero energy floating around our industry developed by world-renowned organiza- tions like the U.S. Department of Energy, and national laboratories like the National Renewable Energy Labo- ratory. Simply put, a zero-energy building, also known as a zero net energy building, or a net-zero energy building, is a building with zero net energy consump- tion, meaning the total amount of energy (electricity, gas, chilled water, steam, etc.) used by the building on an annual basis is equal to the amount of renewable energy generated on-site. The International Living Future Institute’s Zero En- ergy Building certification requires 100% of the build- ing’s energy needs on a net annual basis be supplied by on-site renewable energywithout the use of on-site combustion (i.e., all-electric buildings). Architecture 2030 (goals adopted by the American Instituteof Architects) allowspurchasingapprovedoff- site renewableenergyand/or renewableenergycredits but onlyupto20%of abuilding’s remainingenergyuse to meet their definition of a carbon-neutral building – a building that uses no fossil fuel, greenhouse-gas-emitting energy to operate. This defini- tionmakes it possible formore buildings to achieve ZNE, even with poor solar access or other site and roof area constraints. We do not know what final definition the cities of Denver or Boulder will end up with as part of their net-zero energy codes as conversation among experts and advocates have introduced alternative termi- nologies like net-zero carbon and net-zero emissions codes. These are currently under con- sideration. There is no shortage of articles, guides, books and organizations dedicated to net-zero buildings if one is interested, and regardless of which definitionwe’d like to adopt for our project, achieving ZNE comes down to implementing two steps (in addition to hiring an A/E team that has the expertise, creativity and commit- ment needed to achieve zero energy goals): 1. EUI reduction orminimization. 2. Offsets using renewable energy: a. On-site predominantly; and b. Off-site secondarily (no more than 20% per AIA’s 2030 Commitment Program). EUI stands for energyuse intensityexpressed inkBtu per square foot per year. It is the energy use per sf at a property (energy divided by sf). EUI enables us to com- paredifferent sizedbuildings. Other common terminol- ogies to keep inmind: • Site energyuse – the annual amount of all the ener- gyyour property consumes on-site, as reportedonyour utility bills. • Source energy use – a more accurate representa- tion of a building's energy footprint as it considers the site energy as well as the energy lost during produc- tion, transmission and delivery to the site. Nevertheless, a low EUI is needed to achieve ZNE. With that said, there are some building types that set up better for ZNE than others. For example, in Colora- do the most energy-intensive (high EUI) building types are restaurants, health care facilities, hotels and data centers, where achieving ZNE will be challenging (not impossible) since there may be not enough roof area available to offset the energy the building uses. ZNE likelihood also is limited by the building’s height and the number of floors in the building that some urban sites might demand. ZNE is easier to achieve on ware- Mohit Mehta, LEED AP BD+C Principal/ Building Performance Director, ME Engineers It’s All About the Carbon What is an energy model? Source: AIA – An Architect’s Guide to Integrating Energy Modeling in the Design Process.