Page 178 - The Green Building Bottom Line The Real Cost of Sustainable Building

LEARNING FROM A LEED PILOT PROJECT 157

The green roof area added an additional $80,000—about $9 additional per square
foot—to the cost of the Shops 600 roof. Using the thicker roof membrane (60 mil
rather than 45) cost 30 cents more per square foot ($2,700).
A solar panel on the roof provides tenants with hot water that is stored for use in an
insulated tank on the ground floor. An auxiliary heating unit ensures a steady temper-
ature, so the water is consistently hot, even on cloudy days. Although this system cost
us $8,000 to get operational, we calculate our net additional expense was about $3,000,
since we didn’t have to buy an individual water heater for each store’s bathroom (one
per store, for a total of six) and have them installed. It just didn’t make sense, from an
environmental standpoint, to use electricity to heat water for hand washing (the only
thing a retail store uses hot water for), even though the costs of heating the water
would be borne by the tenants, not us, as part of their electric bills. Because of the cen-
tral solar hot water system, water in the building is not individually metered.
The bright white parking lot also helps to mitigate the heat island effect by reflect-
ing rather than absorbing sunlight. It’s made of concrete with a high fly ash content.
Fly ash is a residue generated in coal combustion. In the past, fly ash was released into
the atmosphere from the smokestacks of coal-burning power plants, but new pollution
control equipment has made it possible to capture the fly ash from the chimneys before
it gets into the air. It is stored on-site at power plants. Naturally white, fly ash can be
added to supplement portland cement in concrete production. While not exactly a
green product (since it does, of course, come from coal), fly ash that wasn’t captured
would be a particulate pollutant, and using it in concrete provides a market for an
industrial by-product. We were able to obtain high fly ash concrete from a local con-
tractor. It costs about the same as regular concrete.
An infiltration ditch that skirts the parking lot allows stormwater runoff from the
parking lot to percolate through vegetated runoff ditches called “bioswales,” which are
depressions around the perimeter of the pavement with plants and rocks that act as
dams, capturing and filtering the water naturally, purifying it in the process, and even-
tually returning it to the water table. The garden roof, the infiltration ditch, and a strip
of porous paving behind the building allow 100 percent of the stormwater from the
site to infiltrate and re-charge the water table.
The building’s green roof, tight envelope, solar hot water heating, and high-effi-
ciency HVAC units reduce tenants’ electricity consumption by over 25 percent when
compared to a conventional building, and the building’s core energy use operates on
100 percent green power.

The Green Consequences of Green

Retail Development

One of the still-persistent mythologies of green development is that it costs a great
deal more to do a project to LEED standards as compared to conventional construc-
tion criteria. This was true for early LEED projects. Today, however, we can deliver a