BUILDING ENVELOPE STRATEGIES FOR THE
SUCCESSFUL EXECUTION OF A ZNE PROJECT
by Heather Dorer, Mechanical Design Engineer and Rafi Karim, EIT, LEED AP BD+C
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s new federal and state
legislation develops to push
increased energy efficiency in
buildings, building energy codes are
becoming more ambitious and stringent.
The California Energy Commission has
specified a goal that all new homes will
be zero net energy (ZNE) by 2020, and
commercial buildings will be ZNE by
2030. The Department of Energy defines
a ZNE building as “An energy-efficient
building where, on a source energy basis,
the actual annual delivered energy is less
than or equal to the on-site renewable
exported energy.” This means that
enough energy must be generated onsite
(using renewable sources) to offset 100%
of the energy used by the building during
a 12 month period, including any losses
due to distribution and generation at the
power plant level.
To meet this ambitious ZNE goal,
feasible strategies for minimizing energy
use must be pursued, which requires
a comprehensive building design
approach. While the selection of the
energy-consuming devices falls under
the jurisdiction of the mechanical,
electrical, plumbing, and technology
(MEPT) disciplines, successful execution
of a ZNE building starts at the project’s
inception – when building layout,
massing, and architectural features are
being developed.
The ultimate goal is to reduce the
energy demand from heating, cooling
and lighting loads. The heating load
can be reduced by minimizing the loss
of heat and utilizing solar heat during
the winter. The cooling load can be
reduced by minimizing heat gain from
the ambient air and utilizing the wind
for heat removal during the summer.
The lighting load can be reduced by
using natural light to the greatest extent
possible.
The following items summarize
architectural design features which
impact energy use, as well as strategies
that could be incorporated into the
design at the concept design phase to
aide in the successful execution of a
ZNE building.
Location
For most applications, the general
region is predetermined and therefore
the region isn’t included as part of the
decision making process for achieving
a NZE design. The specific site location,
however, will heavily influence the
design, which is why it is necessary
to perform a thorough site location
analysis1. The purpose of a site location
analysis is threefold—to determine
if a site is suitable for the project, to
identify how to incorporate location
attributes into the building design, and
if applicable, to compare multiple sites
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