The U.S. Department of Energy defines a zero energy building (ZEB) as one that produces enough renewable energy (electricity, fuel combustion) to meet its own annual energy consumption requirements. The building terms “net zero energy” and “zero net energy” are synonymous and are broadly used in the industry.
Energy consumption is averaged over a one-year period. The measurement of energy consumed and energy exported is highly dependent on the site boundary, which could encompass a single building or a cluster of buildings. Not just a building, but a campus, a portfolio, or a community can be zero energy.
Title IV of the Energy Independence and Security Act draws a line in the sand, challenging the building industry — which accounts for 38 percent of total U.S. energy consumption, according to DOE — to build net-zero only buildings after 2025 and retrofit pre-2025 buildings to net-zero by 2050.
California, the world’s environmental leader, has set more aggressive goals, requiring all new residential buildings to be ZNE by 2020, new commercial buildings to be ZNE by 2030, and 50 percent of existing commercial buildings retrofit to ZNE by 2030. Both the federal government and California acknowledge that the zero-net energy goals are ambitious, pointing to the elimination of fossil fuel combustion for generation of heat and hot water as very difficult to implement…