Discovery Guides Areas


Green Buildings: Conserving the Human Habitat
(Released October 2006)

  by Ethan Goffman  


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Water, Water Everywhere


We humans emerged from the water and are, in fact, two thirds water. No green builder should overlook this substance most basic to ecosystems, human life, and habitat. Less than 3% of the earth's water is freshwater, and this is subjected to increasing pollution; moreover, aquifers and other water sources are dangerously low and being used faster than they can be replenished. How a building uses, conserves, reuses, and expels water goes a long way toward determining its environmental impact. The CSA Discovery Guide Domestic Water Conservation: Greywater, Rainwater and Other Innovations ( explains ways to conserve and reuse this vital resource. According to the U.S. Green Buildings Council, water efficiency "can be achieved through reduced water consumption fixtures, on-site treatment of wastewater and use of rain catchment or graywater for irrigation and for toilets."47

Buildings are part of a larger environment, and runoff from roofs and surfaces greatly impacts the surrounding area, ending up in small tributaries and eventually in larger bodies of water. On the east coast of the United States, for instance, the oft-cited problems with the Chesapeake Bay have their origins in numerous small streams taking in runoff from built areas. As much as possible, buildings should attempt to maintain an area's natural hydration, making exterior surfaces of permeable materials that allow rain to soak into the ground below. Green roofs as well as rain gardens (for instance at the edge of parking lots) prevent excessive and unnatural water flow, while rain barrels may capture water and preserve it for watering vegetation and other uses.

lovely, colorful yard
Xeriscaping can greatly reduce water use

Because grass lawns consume an inordinate amount of water, particularly in hot, dry climates to which they are not native, xeriscaping is an option that allows water conservation. Preserving plants already in the area will minimize the amount of care needed. Local grasses and wildflowers are common choices.

Inside of buildings, beyond basic measures to avoid excessive water use, the reuse of impure water, known as greywater, is another common practice. Of course such water cannot be used for drinking or cleaning, but must be reserved for toilets and gardening.

In 1989, Massachusetts became the first U.S. state to require low-flush toilets, which have since become standard. Pre-1980 models could use as much as 7 gallons per flush; today's low flush toilets use only 1.6 gallons.48 Concerns about a weak flush have since been alleviated; there's now even a dual option with a stronger flush. Home toilets rely on gravity and pressure, while commercial buildings use flushometer toilets that require a big supply pipe. Leaking toilets are a big concern; one such toilet "can waste up to 18,000 gallons of water in a year."49

cutaway diagram of toilet
Anatomy of a low flush toilet

Means of conserving water, then, are numerous and should harmonize with natural processes. The Fayettesville Public Library, "the first building project in Arkansas to be registered with the U.S. Green Building Council," for instance, "introduced waterless urinals, a cistern to capture and reuse rainwater for irrigation, and native and drought tolerant landscaping."50 Such multiple strategies are critical to any well-conceived, integrated green building.

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