Zero-energy building
A zero-energy building (ZEB) is designed to produce at least as much energy as it consumes annually, effectively balancing its energy needs with on-site energy generation. This concept is part of the broader green building movement, which aims to minimize environmental impact through sustainable construction practices. ZEBs typically employ renewable energy sources, like solar and wind, while also focusing on energy efficiency measures, such as superior insulation and strategic building design to reduce energy consumption.
Interest in ZEBs has surged due to environmental concerns and a desire to decrease reliance on fossil fuels, particularly in light of global instability in oil-producing regions. The first commercial zero-energy structure in the United States was built at Oberlin College in 2000, paving the way for further development in this area. However, challenges remain, especially for larger buildings, as maintaining energy efficiency becomes more complex.
While there is no official standard for defining ZEBs, the U.S. Department of Energy has provided a guideline stating that ZEBs must generate enough renewable energy to meet their own consumption needs. As sustainable construction continues to evolve, the pursuit of zero-energy buildings reflects a growing commitment to environmental stewardship and energy independence.
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Zero-energy building
A zero energy building (ZEB) produces at least enough energy each year to meet all the needs of the building and its inhabitants or users. The zero energy model includes efforts to create on-site energy and reduce energy consumption. Environmental concerns and the development of improved technology for energy production increased interest in ZEBs. Individual homeowners and some commercial enterprises have created zero energy structures. However, those pursuing this model face challenges in the development of larger, taller buildings that can take advantage of zero energy strategies and the significant investment involved in zero energy infrastructure.
Background
ZEBs are part of the movement toward green building, or construction practices that try to lessen structures' effect on the environment. Green building uses renewable resources, such as woods that grow quickly or are recycled from other structures. It involves efforts to conserve energy, such as using good insulation and installing large windows that allow sunlight to help warm the home. Green builders take steps to reduce the consumption of natural resources. They may use solar energy for power or create water catchment systems to recycle rainwater for household purposes. In the last decade of the twentieth century, interest in such efforts grew, and builders worked to create structures that completely offset their own energy needs. The first zero energy commercial structure in the United States was a building on the campus of Oberlin College constructed in 2000.
Green building supporters have defined ZEBs in different ways. Some have considered any buildings that greatly reduced their energy consumption to be ZEBs. For example, this definition would include buildings that primarily use solar energy but have a gasoline-powered generator as a backup. Other definitions consider various aspects of the building's energy consumption. For example, a zero energy cost building produces enough energy for export to the power grid to cover the cost of its own energy usage, while a zero energy emissions building generates enough emissions-free renewable energy (such as solar or wind) to offset emissions, or waste products, from any fuels it uses on-site.
Some ZEBs are referred to as net-zero energy buildings. These buildings sometimes use fuels that cannot be produced on-site, such as oil or natural gas. However, the buildings generate enough energy in some other form—such as solar or wind energy—not only to provide for the building's own needs but also to offset the units of energy from other fuel sources. Net-zero energy construction is more attainable than zero energy construction. The ZEB at Oberlin College is a net-zero structure. Many home construction companies have begun specializing in net-zero construction as well.
Although the concept of ZEBs is so new that no official standards have been set to quantify whether a building meets zero energy standards, the US Department of Energy established a definition for ZEBs in September 2015. It states that a ZEB generates enough renewable energy on an annual basis to meet its own energy consumption needs. In doing so, ZEBs reduce the amount of nonrenewable energy used.
Overview
Interest in ZEBs has grown for several reasons. Research has shown that about 40 percent of all the energy used in the United States powers and/or heats homes and commercial structures. As a result, these buildings are sources of a large amount of environment-harming emissions and pollution. Concern for the environment has led some to consider the ways people use natural resources, including fuel sources, and to look for alternatives that conserve or avoid the use of these resources to reduce emissions. Frequent instability in oil-producing regions of the world has prompted people to look for ways to minimize dependence on oil and oil-related products. Others have sought to reduce the cost of operating larger structures that consume much energy for heating and cooling and have turned to energy generated by the sun, wind, or water. Excess energy generated by these environmentally friendly sources usually can be sold to power companies for distribution over the commercial power grid.
A number of steps can be taken to help create a net-zero energy building or ZEB. These steps generally fall into two categories: using more renewable energy sources and reducing the amount of energy needed. Energy needs can be reduced through good building design. For example, a building may be positioned to take advantage of passive solar heat entering through windows, or a structure may be built so more of it is underground to take advantage of Earth's natural insulation. Using extra energy-conserving insulation and efficient seals to maintain as much warm or cool air as possible reduces that amount of energy a building needs. Selecting energy-efficient appliances and systems also decreases the amount of energy needed. Once these steps are taken, energy sources such as solar and wind can more readily provide for the needs of the building and its occupants.
One of the main challenges to zero energy construction is the difficulty of building larger, taller structures that can run efficiently on zero energy principles. For instance, it is relatively easy to design a two-story structure that can generate enough energy for its own needs, but it is much harder to accomplish this task for a structure that is four or more stories. Instead of having large high-rise structures that make efficient use of square footage on the ground, zero energy structures need to sprawl over larger expanses of land. This can be problematic in cities. Experts say that it is better to have a city neighborhood full of energy-efficient homes than to have one large building that is zero energy amid many that are less efficient. Therefore, it becomes a matter of determining whether financial resources are better used to encourage energy conservation methods, such as good insulation and efficient heating and cooling systems, in many buildings or to create a few ZEBs.
Bibliography
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Crawley, Drury, et al. "Getting to Net Zero." National Renewable Energy Laboratory, Sept. 2009, www.nrel.gov/docs/fy09osti/46382.pdf. Accessed 25 Nov. 2017.
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