Report
Analyzes Energy Performance of COTE Top Ten Green Projects
Energy Star based comparisons show
good direction toward 2030 Commitment
Summary: The
2009 Summer Research Scholarship, cosponsored by the AIA Committee
on the Environment (COTE) and American Institute of Architecture
Students (AIAS), went to Berkeley MArch candidate and graduate student
instructor Nathan Brown, who focused on calculating the source energy
performance of 28 COTE Top 10 projects and analyzing their performance
against the baseline established by the Energy Star database of buildings
with similar functions and weather conditions.
The intent of COTE advisors in directing this research was to establish
a foundation for post-occupancy documentation of building performance
overall and energy performance in particular for several COTE
Top Ten projects. The final
report is posted on the AIA COTE Web site.
Brown explains in his abstract:
Actual energy-use data were gathered
for 28 projects for all fuel types. These energy use data are then
compared to the energy use of a typical building of a similar type
using Portfolio
Manager, either by calculating an Energy Star
rating or by comparing the energy use to a national average for
a similar building type. The researcher develops a methodology
to study buildings further as cases, including a set of interview
questions to identify important points in the design and delivery
of a building that may affect its actual energy use. From the list
of buildings with Energy Star ratings, three were selected for
the case study phase. The researcher then conducted a series of
phone interviews, revealing crucial aspects of each design process.
Source energy versus site energy
One of the first elements of the study that Brown explains in his
report concerns the 2030 Commitment to reduce carbon emissions
and the foundation of the Energy Star methodology; specifically,
the difference between site energy and source energy. Site energy
use, which can be readily measured through changes in utility bills,
is the energy consumed by a building. Site energy use, however,
does not measure the energy expended to generate electricity and
transmit and distribute it to the building. The key loss in this
equation is in the conversion of the primary energy, such as the
heat from burning fossil fuels, to electricity. As
averaged for all fuel inputs for the U.S. in 2008, 63 percent of
the primary energy is lost during the conversion of heat into electricity—for
instance, the energy lost in turning the steam-powered turbines.
Another 2 percent goes to ancillary operational aspects of the
energy plant. Transmission and distribution of the electricity
accounts for another 3 percent reduction from the primary energy
generated. (For the case of this study, Brown ties carbon emissions
directly to energy consumption and equates the 2030 Commitment
of an immediate reduction of energy consumption by 50 percent to
source energy, not site energy. By extension, he equates the 2030
goal of zero emissions to “net zero source
energy.”)
![](1030p_cotetop10.jpg)
The implications of this a priori energy loss factor are that calculating
net zero source energy is not as straightforward as simply subtracting
energy produced from energy consumed. Rather, one must inflate the
energy purchased from a utility to account for these losses. Electricity
sold to the grid and electricity purchased from the grid are not
equivalent. As Brown notes: "A building may be considered a
net zero source energy building if the renewable energy produced
on site is greater than or equal to the source energy used by the
building."
Taking this point a step further in his conclusions, Brown points
out that further study would need to be done to account for embodied
energy. For instance, the energy used by the manufacture of on-site
renewable energy production, such as photovoltaics, could become
an important factor when comparing the elimination of building systems
with offsetting electricity use with renewables, he says.
Conclusions
The endless accounting complexities aside, Brown does develop six
lessons learned. Taken straight from his report, his conclusion
reads:
Low-energy performance as a design goal
The development of goals and the advocating for goals is a significant
consideration that may, in some cases, trump the effectiveness
of an integrated team. In the case of the International
Fund for Animal Welfare, its above-average energy performance seems to have
been motivated by responsible design principles and LEED™,
with some benefit being generated by the integration of the contractor
in the process of developing mock-ups. It seems that the exceptional
performance of that building is in its preservation and restoration
of wildlife habitat, reflecting the project’s top goals.
In the Terry
Thomas, since the architect was planning on being a
tenant and since a triple net lease was negotiated, there was motivation
for the architect to design a highly efficient building. Thus, when
a contractor was unfamiliar with the construction process for the
sunshades, the persistence of the architect became important: it
took multiple rounds of communication to reach an appropriate price
for the shades. While the contractor was not closely integrated early
on in this aspect of the design process, the persistence of the architect
in achieving a goal proved decisive.
In the IRS Kansas City Service Center, the
performance goals of the project were established very early in the
design process through the negotiation of the lease. Whether these
goals were as aggressive as they could have been seems to be an open
question, but the establishment of specific performance goals that
were tied to the targets of project cost eliminated the need for
value engineering later in the design process as long as the design
met the performance goals.
These projects not only underscore the importance of establishing
goals for performance, they also show a variety of sources of motivation
for energy performance.
Communication through mock-ups
Mock-ups were used in both the IFAW and IRS Kansas City Service Center.
In each of these cases, there was some impact related to energy
performance. At IFAW, electric lighting was reduced when a system
of daylight reflection was verified. In order to reduce solar loads
at IRS, a glazing modification was assembled as a mock-up to test
its assembly and effect on the aesthetics of the design. Lastly,
it seems that a mock-up might have been useful in both the Chartwell
School and the Terry Thomas projects in order to facilitate communication
between the architect and the contractor regarding the design of
critical sustainable features. In Chartwell, a mock-up of the skylights
would likely have resolved the issue of the added “curb” [which
blocked light, negating the value of the light well] before it
was constructed in the building. In the Terry Thomas, a more reasonable
cost for the sunshades would likely have been achieved earlier
had a mockup been done to allow the contractor to gain familiarity
with the design.
Importance of the role of the designer
The Terry Thomas and the IRS Service Center show that the role of
the designer is essential in integrated design. In the Terry Thomas,
while team members were available from the start to provide a variety
of feasible strategies and expert advice and analysis, it was the
role of the designer to weave various interests and strategies
together to form a coherent design proposal. This becomes a strategy
in itself when the sustainable features become inseparable from
the overall architectural proposal from the building; a courtyard
is not likely to be lost in value engineering. In the IRS project,
while a detailed energy model was completed by the contractor and
used to assess and select low-energy strategies, the architect
relied on experience and intuition in incorporating specific strategies
in the final design.
Elimination of systems
There were multiple examples of design teams not simply reducing
the size of systems, but designing to eliminate them altogether.
In the Artists
for Humanity EpiCenter project, in Chartwell School,
and in the Terry Thomas, for instance, air conditioning was eliminated
from the project entirely. A system that doesn’t exist will
use zero operational energy and contains no embodied energy. It
is no surprise then that Chartwell is the highest scoring building
in the study. After a year of typical energy use data, the Terry
Thomas will likely be a top performer as well. The challenge for
design teams then becomes understanding the climate and life of
the building in order to characterize and communicate the effects
of eliminating air conditioning. If the daily and yearly behavior
of the naturally ventilated building can be described, imagined,
and accepted, this will go a long way towards reducing energy use
in future projects.
Commissioning of systems and follow-through of the owner and/or
facilities manager
In the examples where projects were subject to commissioning, it
helped ensure that building systems were working efficiently. On
the other hand, some projects suffered as a result of not having
systems commissioned carefully. Likewise, it is important for the
owner or manager of the building to remain invested in its energy
performance over time. In the example of one house, energy use had
steadily risen as systems were not maintained over time. When the
systems were tuned and adjustments made, the house saw its energy
use cut in half. This point underscores the limitation of actual
energy use in assessing the sustainable qualities of a design, since
the architect has no control over occupant priorities and behavior.
Metering and reporting of data
A study cannot evaluate what was not measured. Several Top Ten projects
were not included in the dataset for this study because there were
no data available. Reasons for this included no meter being installed,
the meter was not maintained, or the owner was not willing to share
data. If it is a future goal for the performance of green buildings
to be studied more extensively, then it should become standard
to monitor energy use in green buildings and for that information
to be readily and publicly available. |