A zero-energy
building, also known as a zero
net energy (ZNE)
building, net-zero energy building (NZEB), net zero building or zero-carbon building is a building with
zero net energy
consumption, meaning the total amount of energy used by the building on
an annual basis is roughly equal to the amount of renewable energy created
on the site, or in other definitions by renewable energy sources
elsewhere. These buildings consequently contribute less overall greenhouse gas to
the atmosphere than similar non-ZNE buildings. They do at times consume
non-renewable energy and produce greenhouse gases,
but at other times reduce energy consumption and greenhouse gas production
elsewhere by the same amount. A similar concept approved and implemented by
the European
Union and other agreeing countries is nearly Zero Energy Building (nZEB), with the goal of having all
buildings in the region under nZEB standards by 2020.
The most cost-effective steps toward a reduction in a
building's energy consumption usually occur during the design process. To
achieve efficient energy use, zero energy design departs significantly from
conventional construction practice. Successful zero energy building designers
typically combine time tested passive solar,
or artificial/fake conditioning, principles that work with the on-site assets.
Sunlight and solar heat, prevailing breezes, and the cool of the earth below a
building, can provide daylighting and stable indoor temperatures with minimum
mechanical means. ZEBs are normally optimized to use passive solar heat
gain and shading, combined with thermal mass to
stabilize diurnal temperature variations throughout
the day, and in most climates are superinsulated. All the
technologies needed to create zero energy buildings are available off-the-shelf today.
Sophisticated 3-D building energy simulation tools
are available to model how a building will perform with a range of design
variables such as building orientation (relative to the daily and seasonal
position of the sun),
window and door type and placement, overhang depth, insulation type and values
of the building elements, air tightness (weatherization),
the efficiency of heating, cooling, lighting and other equipment, as well as
local climate. These simulations help the designers predict how the building
will perform before it is built, and enable them to model the economic and
financial implications on building cost
benefit analysis, or even more appropriate – life cycle assessment.
