Zero Energy Buildings
A zero energy building [ZEB] is one with a net energy consumption
of zero over a typical year in terms of:
- Energy cost
- Energy consumption
- Carbon emissions
Energy balance requires both energy generation and energy conservation.
In calculating the net energy rating, consideration must be given
to emissions generated in the construction of the building and energy
embodied in the structure which can invalidate claims of reducing
Some buildings even produce a surplus of energy to requirements.
These are known as 'energy-plus' buildings.
In practice, there are a wide range of energy ratings applied to
Net zero cost - where the price of energy from
offsite sources equates to income from sales of electricity to the
grid of electricity generated on-site.
Net zero site energy use - the amount of energy
provided by on-site renewable energy sources equals to the amount
of energy used by the building.
Net off-site zero energy use - energy used by
the building is purchased from offsite, 100% renewable energy sources.
Net zero primary energy use - accounts for the
inefficiency of off-site generated energy, particularly electricity.
Electricity is only around 35% efficient, and further losses [7.2%-7.4%]
occur during transmission. Hence, to reach a zero definition for
primary energy use, the amount of electricity exported must be substantially
higher than the amount of energy brought in.
Net zero energy emissions - also known as a zero
carbon building or zero emissions building. Carbon emissions generated
from on-site or off-site fossil fuel use are balanced by the amount
of on-site renewable energy production.
Off-the-grid - an autonomousself-sufficient Zero
Energy Building that is not connected to any off-site energy supply.
This requires both renewable energy generation and energy storage
Balancing energy conservation and point-of-use renewable energy
generation [solar energy, wind energy, etc.] is hotly debated. The
aim of most zero energy designers is to design a building that:
- Uses zero energy
- Produces zero emissions
- Minimises all energy use
- Minimises damge to the environment
The debate is around which element is more important than the others.
Regardless of individual opinion, more important is the understanding
that a zero energy building does not result from a single product
or technology, but rather a group of closely-integrated technologies.
Thus design must be approached from a whole-house energy-consumption
perspective. Each component must work efficiently and cost-effectively
with all other parts, to achieve maximum energy savings, as well
as the living needs of the occupants.
Annual net energy bills, and contribution to pollution are only
partial measures of zero energy building success. Wider acceptance
of zero energy building technology will likely require more government
incentives or building code regulations, as well as development
of recognised standards.
The World Business Council for Sustainable Development has launched
a major initiative to support the development of ZEB.
Zero Energy Building versus Green Building
The goals of ZEB and Green Building are both congruent and disparate.
ZEB design criteria involve major reduction, and eventual elimination
of, energy bills and greenhouse gas emissions.
Green building aims to reduce the impact of new buildings on the
environment, while improving environmental sustainability. Green
architecture, sustainable design, and natural building all embrace
similar goals and solution concepts.
Detailed knowledge of zero energy design is less common than Green
Building, with many design and building certification programs deficient
in coverage in these areas. In addition, computer models used to
evaluate Green Building design do not include the thermal science
and architectural design patterns necessary to evaluate passive
solar building design or zero energy design.
Once constructed, most ZEBs are very “green,” but very
few Green Buildings are off-the-grid, or use zero energy. Governments
are slowly developing minimum performance standards that recognize
the availability of zero-energy technologies for high-performance
Back to Top
Sustainable Homes Index | Defining
Sustainability | Energy Efficient Homes
Energy Buildings | Sustainable Home
Design | Energy Efficient Appliances
| Heating | Active
Solar | Passive Solar | Solar
Water Heating | Geothermal
| Lighting | Water
Management | Updates