and/or building configurations which
are being considered. Below is a list of
attributes which must be noted when
performing a site location analysis. The
strategies for optimizing the building
design in accordance with these
attributes will be summarized in later
sections.
• Geography and local climate: The
angle of the sun with reference to the
project site will determine the angle
at which solar panels are mounted
and the angle of the window
shading. The wind patterns will
impact how the building orientation
can be optimized to maximize
exposure to prevailing winds to
utilize cross ventilation. The outdoor
air quality will determine if natural
ventilation is possible and/or if
excessive filtration is necessary. The
presence of excessive local noise will
determine if operable windows can
be used given the potential for the
building occupants to be distracted.
• Meteorology: The annual hourly
heating and cooling temperatures
will determine if natural ventilation
is feasible for a sizeable portion of
the year or if thermal mass will be
a good strategy. The anticipated
precipitation will determine the
feasibility of rainwater harvesting
for irrigation purposes. The
anticipated humidity will determine
if passive cooling will be effective
or if a cooling system which
utilizes condensate recovery can be
implemented.
• Topography: Shading due to nearby
buildings, trees, and hills will impact
the heating, cooling, and lighting
loads.
• Geology: The temperature of
the ground as compared to the
temperature swings of the ambient
air and annual heating and cooling
degree days will determine the
feasibility of ground source heat
pumps.
6
Building Shape
The building shape includes the building
dimensions and configuration, as well
as the orientation of each face with
respect to the surrounding environment,
and should be designed with the site in
mind. If the space will be mechanically
cooled and won’t realize much benefit
from passive ventilation then it is
advantageous to have a compact
building, which will provide less surface
area for heat transfer for a given building
volume2. That being said, minimizing
the roof area will also reduce the amount
of useable area for photovoltaic panels.
If the potential for passive ventilation is
significant, it is advantageous to have
a long and narrow building that is
oriented in the direction of the expected
wind stream3.
Glazing (Glass)
Glass has poor thermal resistance,
meaning that it is easy for heat to pass
through glazed area. Strategic planning
of the glazing layout and glass selection
will permit adequate access to light while
minimizing heat transfer.
• Window-to-Wall Ratio (WWR,
total percentage of wall area that is
glazed): For energy purposes, a lower
WWR is ideal in a cooling climate,
but for daylighting purposes, a
higher WWR is ideal. An optimized
solution can be reached through the
use of shading, quantity of glazing
allocated to each building face, and
daylighting controls. In general, a
WWR of 30-40% is ideal.
• Glazing Configuration (percentage
of wall area that is glazed per face):
An optimized design strategy is to
concentrate the glazing on the south
side of the building with horizontal
shading above the windows.
This is further explained in the
shading section.
• Glazing Performance: The
prescriptive criteria for vertical
fenestration in nonresidential
buildings as defined by Table
140.3-B of Title 24 Section 6 are
summarized in Table 1 below. Glass
with high thermal performance
will have4:
• A low rate of convective heat flow
(U-factor), which is achieved
by having multiple panes and
a cavity filled with gas, which
serves as an insulator. Triple
paned is superior to double
paned, and an argon-filled cavity
is superior to an air-filled cavity.
• A low-emissivity (low-e) coating.
In general, glass that has a low
emissivity will be more reflective
as compared to glass with a
higher emissivity5.
• A low solar heat gain coefficient
(SHGC, which is the fraction
of solar radiation admitted
through a window) on the east,
west and south faces. It should
be noted that a low SHGC
tends to be darker and therefore
comes at the expense of the
visual transmittance, which can
adversely impact the daylighting
and occupant experience in the
space. For aesthetic purposes, a
higher visual transmittance (VT)
is ideal.
Table 1: Prescriptive criteria for vertical
fenestration in nonresidential buildings as
defined by Table 140.3-B.
Parameter
T24 Value
Max U-factor
Max SHGC
0.36
0.25
Max WWR
Min VT
40%
0.42
Shading
Shading complements the glazing layout
to reduce heating and cooling loads. One
strategy is to include horizontal shading
panels on the south face. This reduces
solar cooling load during the summer,
as the sun is higher in the sky and is
therefore blocked by the shading panel1.
The heating load will also be reduced
during the winter, as the sunlight
approaches the building at a lower angle,
thereby allowing the light to penetrate
the building through the windows and be