How can a building be zero-energy?

A zero-energy building, also known as a zero net energy (ZNE), is a building with zero net energy consumption, meaning that the total amount of energy used by the building on an annual basis is roughly equal to the amount of renewable energy created on site.  Maximizing energy efficiency practices plays a vital role in the design and implementation of zero-energy buildings. Due to the timing of energy demand and supply at the facility, ZNE buildings often are still connected to the local utility energy grid so as to continually meet energy needs. 
 
An example of this is the Zero Net Energy Center training facility in San Leandro, California.  Energy efficiency features used to achieve zero net energy include natural day lighting through operable skylights, exterior windows, and solar light tubes; a thermal mass effect that provide energy storage in concrete floors and walls and are heated through roof-top monitors; natural ventilation and direct wind space conditioning through operable windows; and renovation of an existing building in a light industrial zone to minimize the impact on virgin resources and land.  Technology features include LED and highefficiency fluorescent lamps; daylighting and occupancy sensors to reduce loads; a Variable Refrigerant Flow system to efficiently control room temperature and distribute temperature change throughout the building as needed; occupancy sensors to enable energy usage only when a space is occupied; plug loads minimized through the use of energy efficient equipment; integration of systems to verify and maintain the building’s ongoing performance; and building commissioning to verify that building systems are running correctly.
 
These energy efficiency features reduce the buildings need for energy to a level that then allows onsite generation of electricity to cover the buildings energy needs over an annual basis. The building generation features include solar photovoltaic and small wind turbines. See more about this example at www.znecenter.org.
 
Although ZNE has not become typical for construction, an increasing number of buildings are meeting this standard because of current building technologies and design approaches.
 
 
This Green Tip was submitted by Darlene Besst, member of the BOMA OEB Environment Committee.