Simply put, a Net Zero Energy building must have a significantly reduced need for energy, and have the capacity to make up for the balance of it by using renewable technology, such as PV (solar) panels, wind, hydroelectricity or bio fuels. Yet, when defining a building that requires zero energy – or “net zero” the Department of Energy explains a “net zero energy” building is determined by the project’s goals, and can fall into any or all of the four categories below:
- Net Zero Site Energy – The building produces as much energy on site as it uses within a year.
- Net Zero Source Energy – The building produces as much energy from a source as it uses within a year. A source refers to primary energy used to generate and deliver energy to the site.
- Net Zero Energy Costs – The utility company pays the building owner for the energy the building exports to the grid, which is equal to the amount the owner pays the utility company for the energy services during the year.
- Net Zero Emissions – The building produces as much emissions-free renewable energy as it uses from an emissions-producing energy source.
The design process is usually where reduction of the building’s energy consumption begins. Designers take advantage of sunlight, solar heat and the cool temperatures of the earth, and combine them to calculate a method of indoor lighting and stabilizing indoor temperatures. Computer software can help determine how a building will perform using those natural energy resources in relation to the building’s orientation, window and door placement, local climate and more, which can help with cost benefit analysis, financial implications on the building and life cycle assessment.
Solar-powered ranger home at the John Day Fossil Beds National Monument - the first net-zero home in the National Park Service. (Photo courtesy of DJC Oregon)
Once the building has been designed, construction specifications include energy-saving features to enhance the building’s efficiency. Things like added insulation, high-efficiency windows, natural ventilation, skylights and/or solar tubes and solar water heating all depend on climate zones, but can be very effective at reducing a building’s energy intake.
After the building is complete, energy must be harvested. If a building is connected to the grid, extra energy produced by the building may be returned to the grid when it’s not needed, and drawn from the grid when there’s not enough being produced. The building’s primary function – whether it’s a home or business - also impacts how energy is used.
Electricity consumption in the commercial building sector is expected to increase 50% by 2025, and will continue to increase until buildings are designed to offset their energy demand. The U.S. Department of Energy recognizes this, and has established a goal to “create the technology and knowledge base for cost-effective zero-energy commercial buildings by 2025.”