Green Building Rating Systems
Buildings can be awarded as
- Certified (40-49 points),
- Silver (50-59 pts.),
- Gold (60-79 pts.), or
- Platinum (80-100 pts).
There are specific standards tailored to nine categories of structures (also called "occupancies"): Homes, New Construction, Existing Buildings, Commercial Interiors, Core and Shell, Schools, Retail, Healthcare and Neighborhoods (entire developments). Some of the categories have gone through several revisions, while others are still being developed and piloted. Each building project is rated across major criteria, which encompass the construction process, materials and, importantly, the building's ongoing maintenance and operation.
Efficient water use and reuse can earn points under the following LEED criteria:
- Sustainable Sites,
- Water Efficiency
- Innovation and Design Process
In LEED for Homes, for example, in "Sustainable Sites", stormwater retention and green roofs (vegetated roofs) can earn as many as 7 points. In the "Water Efficiency" criteria, rainwater harvesting can be worth 4 points, but only if the storage capacity is enough to capture all water from a 1" rain event falling on 50% of the roofed area. Graywater reuse earns 1 point, but must include a "dosing basin". This means the graywater would have to be pre-treated, which is often quite unnecessary, depending on end use). Using recycled municipal water for irrigation is worth 3 points. High-efficiency irrigation, water-wise landscaping, and high-efficiency indoor fixtures are worth as many as 10 points.
For commercial, retail, institutional, or manufacturing buildings the major criteria remain similar, but the point structures are differ depending on the type of construction and its users. The points available for water conservation and reuse in these other building categories are disappointingly minimal. For example, under LEED New Construction stormwater design earns only one point, and water use efficiency is worth a total of 10 points. As some US states grapple with increasing water supply shortages, LEED will need to place a higher priority on large-scale water conservation.
