Page 175 - Green Building Through Integrated Design

LEED RATING SYSTEM AND EVA 151

TABLE 8.3 SUSTAINABLE SITES: CREDIT 7.2 HEAT ISLAND EFFECT, ROOF
LEED CREDIT SOLUTION
NON-LEED #1 LEED COMPLIANT LEED CREDIT SOLUTION
BUILDING ROOF #2 GREEN ROOF
Soft Cost Impacts None None Structural engineering:
additional design
$10,000
Hard Cost Impacts None Cost increase for 1. Additional structural
LEED-compliant steel $20,000
roofing materials 2. Cost increase for green
$100,000 roofing $400,000
3. Less land needed
for stormwater
retention $200,000
Life-Cycle Benefits None Energy cost reduction 1. Energy cost reduction
$20,000/year $20,000/year
2. Maintenance cost
reduction $5000/year

to take the green roof option off the table just yet. A green roof also contributes to
achieving LEED’s credits for open space and habitat preservation, as well as pro-
viding a vital amenity in an urban environment, viewable for passive recreation or
used for active recreation. As an example of passive recreation, the architecture
firm Cook+Fox in New York City created a green roof on the eighth floor of a 100-
year-old building in downtown Manhattan, as part of a LEED for Commercial
Interiors Platinum tenant remodel. The roof is available for passive enjoyment by
all employees and visitors. While it’s not accessible to the occupants, it is visible
through many of the firm’s windows, providing a vital visual amenity in a heavily
congested urban area.

WATER EFFICIENCY: CREDIT 1—WATER-EFFICIENT
LANDSCAPING
Let’s look at a very different example, addressing the concern for reducing potable water
use for landscape irrigation. Two alternatives are to plant only native/drought-tolerant
species or to collect rainwater and use it for irrigation. In the second option, we add
$80,000 to costs for collecting, treating, and distributing collected rainwater and gray-
water to our irrigation system (Table 8.4). For the first option, we also save $15,000 per
year in purchased water costs and $5000 in irrigation system maintenance, with imme-
diate payback. The second option also yields $15,000 per year savings in water pur-
chases. It requires more than 5 years to pay for itself. In the analysis, the use of native
plants provides the economically superior solution and meets our Triple Bottom Line
goals as well (Fig. 8.3).