A zero energy building (ZEB) or net zero energy building is a general term applied to a building with a net energy consumption of zero over a typical year. Zero energy buildings are gaining considerable interest as a means to cut greenhouse gas emissions and conserve energy. Buildings use 40% of the total energy in the US and European Union.
This can be measured in different ways (relating to cost, energy, or carbon emissions) and, irrespective of the definition used, different views are taken on the relative importance of energy generation and energy conservation to achieve energy balance. Although zero energy buildings remain uncommon in developed countries, they are gaining in importance and popularity. The zero-energy approach is promoted as a potential solution to a range of issues, including reducing carbon emissions, and reducing dependence on fossil fuels. Most ZEB definitions do not include the emissions generated in the construction of the building and the embodied energy of the structure which would usually invalidate claims of reducing carbon emissions. 
Imagine a facility that generates enough energy to meet all its own needs: This is the philosophy behind zero-energy buildings (ZEBs). The concept isn't new, but the implementation is. Zero-energy homes are more the norm than zero-energy commercial buildings, but that may soon be changing. Companies such as San Jose, CA-based Integrated Design Associates Inc. (which is building the Z2 Design Facility highlighted in Building a Zero-Energy Commercial Office) are striving for net zero energy and zero carbon emissions.
As the idea gains traction, researchers work to develop innovative technologies that can make ZEBs a widespread possibility for all future new construction projects. Despite the fact that the application is somewhat limited today, the quest for zero energy remains one of the most dramatic means for reducing greenhouse-gas emissions attributed to commercial buildings. While the term "zero-energy building" has many definitions, it is most often defined as a building that produces as much energy on-site as it consumes on an annual basis. They are actually referred to as net-zero-energy buildings because they do use energy; however, the supply from on-site generation is equal to (or greater than) the facility's demand.
How to Achieve Net Zero Energy A ZEB is only possible if three things happen: 1) the goal is set early and the project team makes integrated decisions, 2) energy consumption is cut dramatically, and 3) an investment in on-site power generation is made. ---> Read more of this article here. 
In the U.S., ZEB research is currently being supported by the US Department of Energy (DOE) Building America Program, including industry-based consortia and researcher organizations at the National Renewable Energy Laboratory (NREL), the Florida Solar Energy Center (FSEC), Lawrence Berkeley National Laboratory (LBNL), and Oak Ridge National Laboratory (ORNL). From fiscal 2008 to 2012, DOE plans to award $40 million to four Building America teams, the Building Science Corporation; IBACOS; the Consortium of Advanced Residential Buildings; and the Building Industry Research Alliance, as well as a consortium of academic and building industry leaders. The funds will be used to develop net-zero-energy homes that consume at 50% to 70% less energy than conventional homes. DOE is also awarding $4.1 million to two regional building technology application centers that will accelerate the adoption of new and developing energy-efficient technologies. The two centers, located at the University of Central Florida and Washington State University, will serve 17 states, providing information and training on commercially available energy-efficient technologies.
According to Energy Design Update (February 2007), one home in the United States has demonstrated 12 months of data showing net-zero-energy performance; that house, located in Wheat Ridge, Colorado, was built by Metro Denver Habitat for Humanity, with help from NREL engineers.
The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should soon demonstrate multiple new technology innovations and mass production of economies of scale. One of the most comprehensive modern compilations of information on this subject is the U.S. Department of Energy (DOE) Oak Ridge National Laboratory (ORNL) Building Technology group "Thermal Performance of the Exterior Envelopes of Whole Buildings Tenth International Conference" held December 2007. The popular Zero Energy Design DOE/ORNL Workshop materials include an 800-page eBook, 500 presentation slides, and related support materials. 
 Source: Wikipedia
 Source: buildings.com