This is the fourth post in a series on the LEED green building rating system. The first post provided an Introduction to LEED, the second looked at the Sustainable Sites credit category, and the third at the Location and Transportation credits.
Fresh, drinkable water is a precious commodity that is only available in a limited supply. Therefore, prudent use and treatment of waste water are very important as we look to expand our built environment and shrink natural treatment areas. Credits under this category have to do with limiting water use, both inside buildings and outside in landscaping.
Outdoor Water Use Reduction
This is a required measure and must be completed to qualify for LEED certification. Reduce outdoor water use by providing landscaping that requires little or no irrigation. The use of native and drought-resistant plant species is encouraged.
The project must use no irrigation (after a two-year establishment period, where temporary irrigation systems are acceptable) or use 30% less than a baseline model. Plant species and the use of drip irrigation systems and moisture sensors are used as strategies to meet this goal.
This is a required measure. Provide fixtures and fittings that will reduce indoor water use by 20% over a baseline case. Water use for fixtures is determined by tables provided in the Reference Guide. All plumbing fixtures should be WaterSense labeled or similar. Calculations should include appliance and process water use.
Building-Level Water Metering
This is a required measure. Provide a water meter to measure water use on a monthly and annual basis, either automatically or manually, and provide such information to the US Green Building Council for a period of five years after the building is occupied or certified, whichever comes first.
Outdoor Water Use Reduction
This credit is worth 1-2 points. Provide no irrigation system (after a two-year establishment period) for 2 points, or reduce the amount of water needed for irrigation by 50% or more over the baseline calculation. Strategies include plant selection, irrigation delivery system, and alternative water sources.
Indoor Water Use Reduction
This credit is worth 1-6 points. Reduce the amount of water needed for indoor fixtures and fittings, similar to the prerequisite above. For each 5% increase in efficiency, from 25% to 50%, a point is awarded. 1 point for 25% efficiency, 2 for 30%, etc. The use of water saving fixtures, such as dual-flush toilets, low-flow urinals, and sensored faucets, are key to earning these credits.
Cooling Tower Water Use
This credit is worth 1-2 points. This credit has to do with the treatment of the makeup water for cooling towers or condensers. Projects with this equipment must perform a water quality test and determine how many cycles the water can go through before exceeding limits for compounds such as calcium carbonate, silicon dioxide, and total alkalinity as per the Reference Guide. Then, the equipment must be set to not exceed the number of cycles calculated (up to 10), and the project earns 1 point. If the water can go through over 10 cycles or if it achieves the first credit and uses a minimum of 20% of recycled nonpotable water, another point can be earned.
This credit is worth 1 point. Provide water sub-metering for additional systems in addition to the main building meter. At least two of the following systems must be monitored to earn 1 point: irrigation, indoor plumbing fixtures and fittings, domestic hot water, boilers, reclaimed water, and other process water.
Next we will focus on the Energy and Atmosphere credit category.
Source: LEED v4 for Building Design and Construction (updated July 1, 2014)