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It's Top Ten season. That means sustainable design metrics have
been tracked and submitted en masse for this year's green projects.
For a closer look at one metric, EPA's energy performance rating is
the key connector for commercial projects' energy use and
greenhouse gas emissions. Portfolio Manager is the tool of
choice for operating projects, and also serves as the LEED-EB
energy metric. It allows users to track multiple energy and water
meters for a facility. Monthly utility data is benchmarked against
past performance and compared with weather-normalized information
from around the country.
 This latter
feature is unique in giving designers and owners a relative sense
of how well their building is operating. The concept is fairly
simple, but quite powerful in the analysis. The US Department of
Energy (DOE) conducts a survey every four years called Commercial Buildings Energy Consumption Survey
(CBECS). This data set represents over 5,000 buildings with a
wide range of functions, locations, sizes, ages, operating
schedules, etc.--a statistically significant sample of the US
building stock. In reviewing this data, the US Environmental
Protection Agency (EPA) established key energy drivers which are
represented by the inputs in Portfolio Manager and customized for
each space type. This analysis yields a 1-100 rating system that
assigns a percentile to a project's energy performance, as compared
with CBECS data. Thus, a building that achieves a rating of 85 is
among the top 15 percent of similar facilities' performance. This
rating is calculated from source energy, which accounts for
transmission and distribution losses of a building's fuel mix.
Buildings that exceed a rating of 75, over 12 consecutive months,
are eligible to earn the ENERGY STAR label.
The space types that can receive an EPA rating in Portfolio Manager
are:
• Bank/Financial Institutions
• Courthouses
• Hospitals (acute care and children¡¦s)
• Hotels and Motels
• K-12 Schools
• Medical Offices
• Offices
• Residence Halls/Dormitories
• Retail Stores
• Supermarkets
• Warehouses (refrigerated and non-refrigerated)
• Wastewater Treatment Plants
Portfolio Manager users can share building data with other users,
one at a time, and the ENERGY STAR website showcases labeled buildings and publishes
aggregate annual savings. In 2007, EPA reported 1,400 buildings
that earned the ENERGY STAR label, up 25 percent from 2006.
Jared Silliker is an associate at The Cadmus Group, an
environmental consulting firm, and a sustainable business MBA
candidate at the Bainbridge Graduate Institute in Seattle. He works
with the architecture community to encourage high performance
building designs through rigorous energy metrics, and writes
for Inhabitat.com, a sustainable
design blog.
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