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Comparative Analysis of Net-Zero LEED was initiated by the US Green Building Council
Energy and Net-Zero Carbon (USGBC) which was established in 1993 (Mehta et al.,
2013). LEED was formed in 1998 and has undergone
Although these two concepts drive towards reducing several revisions and additions with the most recent
the harmful effects of increasing energy consumption version being LEED Version 4 (USGBC, 2015). It is the
and carbon emissions from buildings, they may not be most widely used green building assessment system in
used interchangeably as seen from the definitions. Net- the US. It awards certification at different levels with the
zero energy is concerned with the balance of building base level being ‘LEED Certified’ and the highest level
energy use, which may also have an impact on emissions. being ‘LEED Platinum’. While LEED is not as challenging
Net-zero carbon is more concerned with the balance in as LBC and does not provide net-zero certification, it
carbon/CO2 emissions from a building. Net-zero carbon could provide a good starting point for achieving net-zero
can be achieved through some of the net-zero energy energy as a number of verified net-zero energy buildings
strategies. have LEED Gold or Platunum certification (Cortese and
Higgins, 2014).
The following sections demonstrate how net-zero energy
and net-zero carbon buildings are achieved in the US Green Globes is an alternative building assessment
through various building assessment methods and case system to LEED. It is more interactive and flexible
study examples. than LEED (Kibert, 2012). Green Globes is also a more
affordable green building certification. It differs from
Building Assessment LEED in that it awards points for life-cycle assessment
of building assemblies during the design process. It is
Methods in the US increasingly adopted by industry. The rating system range
from one globe to four globes (the highest certification).
Building assessment systems evaluate the performance
of buildings according to some defined metrics.
LEED and Green Globes do not require a building to be
The metrics, which are sometimes broken down
net-zero energy to achieve the highest certification.
into checklists or made more flexible and open to
As such, they are not as challenging as the LBC. While
interpretation, are required to meet established criteria
both recognize reduction in GHG emissions, they do
to attain certification. A ranking is awarded to a building
not specifically require buildings to be net-zero carbon.
according to how well it performs in comparison with
These rating systems are applicable to new construction,
the listed criteria. Some of the tools assess buildings
retrofits, and different facilities including schools,
holistically based on environmental, social and economic
offices, healthcare, and residential. Building assessment
requirements (Kibert, 2012). These building assessment
certifications should focus not only on initial recognition
systems are instrumental in the design and construction
and short term energy savings but on energy efficiency
of high performance buildings (Kibert, 2012).
and high performance throughout the lifecycle of the
building.
A number of assessment systems exist in different
countries. In the US, the main building assessment
systems are Leadership in Energy and Environmental Case Studies
Design (LEED), Green Globes, and Living Building
Challenge (LBC). Of these three, the most rigorous, A few case studies have been selected to demonstrate
stringent and challenging is the Living Building Challenge. how net-zero energy has been achieved in new and
retrofit projects in the US. New buildings provide a good
The LBC provides certification that covers all the petals opportunity to create energy efficient designs, taking
and imperatives that provide guidance for meeting into consideration various pertinent factors, to attain
the petal requirements (Kibert, 2012). The petals are high performance buildings. There are also opportunities
performance categories that are used to assess the to select the most energy efficient technologies in the
building. Seven petals are used which include Place, design phase that could lead to net-zero energy and net-
Water, Energy, Health & Happiness, Materials, Equity and zero carbon for new buildings. Deep retrofits also have
Beauty (LBC, 2015). The LBC allows partial certification the potential to deliver significant energy savings (IPCC,
in some petals. To achieve full certification, the building 2014) and could result in net-zero buildings. The case
is required (amongst other things) to be net-zero energy studies presented are based on published materials on
and net-zero water with tracking of embodied energy, the buildings, and in some cases, unstructured interviews
and material reuse (LBC, 2015). Although demanding, the with energy experts associated with the buildings.
LBC is achievable and pushes the boundaries for higher
performance green buildings. In addition to minimizing
environmental impacts and reducing energy use, the LBC
encourages the creation of an environment and building
that is educative and inspiring to visitors and users of the
buildings. The LBC specifically recognizes and certifies
buildings for net-zero energy achievement.

ZCB Journal 2015 • Volume 4 25