Net Zero Energy
The Net Zero Energy home (ZEH) takes over where the Passive House leaves off. In the Passive House, energy needs are reduced 80 to 90% by high performance building technologies using added insulation, an airtight building envelope, high efficiency windows and doors, natural ventilation and site orientation. Interior ambient temperature fluctuations are stabilized and energy-using space conditioning is held to an absolute minimum. The Zero Energy Home uses the Passive House Building Standards and other High Performance Building Technologies to significantly cut the home's energy use but in addition, harvests on-site renewable energy systems like solar thermal and photo voltaic to produce energy equal to overall energy demands of the house.
When the balance between energy used by the home and renewable energy produced on-site annually is achieved, the home is considered to be a Net Zero Energy Home. Zero Energy Homes are most often connected to the local electrical grid and are able to export electricity to the utility company when there is a surplus of energy being produced and draw from it when not enough is being generated. It is the overall annual balance that is required to reach the ZEH standard.
A designer of a Zero Energy Home must be both sensitive to the site, making use of naturally occurring resources and also be able to use holistic design principles in addressing the interactions between systems. 3D computer simulation tools are now available to designers to model how a building will perform allowing for building orientation, window and door types, overhang depths, insulation and airtightness. Energy for heating and cooling systems and the plug-loads from lighting, electronics and appliances are also calculated. A prediction about a building’s performance before it is built assists the designer in both engineering and design decisions and in the cost/benefit analysis of a project.
A Zero Energy Home (ZEH) uses renewable energy systems, such as solar electricity and solar water heating and new high performance, energy-efficient construction technologies to create a house that produces enough of its own energy to power all of its annual energy needs.
Would the house be off the grid? Not necessarily. In fact, it's a benefit for the ZEH to be connected to the grid because at times, like on an overcast day, the house may use some energy from the local utility company. Throughout the year however, the ZEH will produce enough energy to send some power back to the utility to off-set the amount purchased resulting in a net-zero annual energy bill.
See our sister website showing the design and construction of a Net Zero Energy Home: www.SiliconValleyZeroEnergyHome.com