LEED-NC Version 2.1 Reference Guide 79 ID EA SS WE MR EQ In the United States, approximately 340 billion gallons of fresh water are with- drawn per day from rivers, streams and reservoirs to support residential, commer- cial, industrial, agricultural and recre- ational activities. This accounts for about one-fourth of the nation’s total supply of renewable fresh water. Almost 65% of this water is discharged to rivers, streams and other water bodies after use and, in some cases, treatment. Additionally, water is withdrawn from un- derground aquifers. In some parts of the United States, water levels in these aquifers have dropped more than 100 feet since the 1940s. On an annual basis, the water defi- cit in the United States is currently estimated at about 3,700 billion gallons. In other words, Americans extract 3,700 billion gal- lons per year more than they return to the natural water system to recharge aquifers and other water sources. On a positive note, U.S. industries today use 36% less water than they did in 1950 although industrial output has increased significantly. This reduction in water use is largely due to the rigorous water reuse strat- egies in industrial processes. In addition, the Energy Policy Act of 1992 mandated the use of water-conserving plumbing fix- tures to reduce water use in residential, com- mercial and institutional buildings. Overview Using large volumes of water increases maintenance and life-cycle costs for build- ing operations and increases consumer costs for additional municipal supply and treatment facilities. Conversely, facilities that use water efficiently can reduce costs through lower water use fees, lower sew- age volumes to treat energy and chemical use reductions, and lower capacity charges and limits. Many water conservation strategies involve either no additional cost or rapid paybacks. Other water conser- vation strategies such as biological waste- water treatment, rainwater harvesting and graywater plumbing systems often involve more substantial investment. Water efficiency measures in commercial buildings can easily reduce water usage by 30% or more. In a typical 100,000-square- foot office building, low-flow fixtures coupled with sensors and automatic con- trols can save a minimum of 1 million gal- lons of water per year, based on 650 build- ing occupants each using an average of 20 gallons per day. Non-potable water volumes can be used for landscape irrigation, toilet and urinal flushing, custodial purposes and building systems. Utility savings, though dependent on the local water costs, can save thousands of dollars per year, resulting in rapid payback on water conservation infra- structure. Water Efficiency Overview of LEED TM Credits WE Credit 1 Water Efficient Landscaping WE Credit 2 Innovative Wastewater Technologies WE Credit 3 Water Use Reduction There are 5 points available in the Water Efficiency category.
Transcript
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In the United States, approximately 340billion gallons of fresh water are with-drawn per day from rivers, streams andreservoirs to support residential, commer-cial, industrial, agricultural and recre-ational activities. This accounts for aboutone-fourth of the nation’s total supply ofrenewable fresh water. Almost 65% ofthis water is discharged to rivers, streamsand other water bodies after use and, insome cases, treatment.
Additionally, water is withdrawn from un-derground aquifers. In some parts of theUnited States, water levels in these aquifershave dropped more than 100 feet since the1940s. On an annual basis, the water defi-cit in the United States is currently estimatedat about 3,700 billion gallons. In otherwords, Americans extract 3,700 billion gal-lons per year more than they return to thenatural water system to recharge aquifersand other water sources.
On a positive note, U.S. industries todayuse 36% less water than they did in 1950although industrial output has increasedsignificantly. This reduction in water use islargely due to the rigorous water reuse strat-egies in industrial processes. In addition,the Energy Policy Act of 1992 mandatedthe use of water-conserving plumbing fix-tures to reduce water use in residential, com-mercial and institutional buildings.
Overview
Using large volumes of water increasesmaintenance and life-cycle costs for build-ing operations and increases consumercosts for additional municipal supply andtreatment facilities. Conversely, facilitiesthat use water efficiently can reduce coststhrough lower water use fees, lower sew-age volumes to treat energy and chemicaluse reductions, and lower capacity chargesand limits. Many water conservationstrategies involve either no additional costor rapid paybacks. Other water conser-vation strategies such as biological waste-water treatment, rainwater harvesting andgraywater plumbing systems often involvemore substantial investment.
Water efficiency measures in commercialbuildings can easily reduce water usage by30% or more. In a typical 100,000-square-foot office building, low-flow fixturescoupled with sensors and automatic con-trols can save a minimum of 1 million gal-lons of water per year, based on 650 build-ing occupants each using an average of 20gallons per day. Non-potable water volumescan be used for landscape irrigation, toiletand urinal flushing, custodial purposes andbuilding systems. Utility savings, thoughdependent on the local water costs, can savethousands of dollars per year, resulting inrapid payback on water conservation infra-structure.
Water Efficiency
Overview of LEEDTM
Credits
WE Credit 1Water EfficientLandscaping
WE Credit 2Innovative WastewaterTechnologies
WE Credit 3Water Use Reduction
There are 5 pointsavailable in the WaterEfficiency category.
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Overview
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Water Efficient Landscaping50% Reduction
Intent
Limit or eliminate the use of potable water for landscape irrigation.
Requirements
Use high-efficiency irrigation technology OR use captured rain or recycled site waterto reduce potable water consumption for irrigation by 50% over conventional means.
Submittals
❏ Provide the LEED Letter Template, signed by the architect, engineer or respon-sible party, declaring that potable water consumption for site irrigation has beenreduced by 50%. Include a brief narrative of the equipment used and/or the use ofdrought-tolerant or native plants.
Credit 1.1
1 point
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Credit 1.2 Water Efficient LandscapingNo Potable Use or No Irrigation
Intent
Limit or eliminate the use of potable water for landscape irrigation.
Requirements
Use only captured rain or recycled site water to eliminate all potable water use for siteirrigation (except for initial watering to establish plants), OR do not install permanentlandscape irrigation systems.
Submittals
❏ Provide the LEED Letter Template, signed by the responsible architect and/orengineer, declaring that the project site will not use potable water for irrigation.Include a narrative describing the captured rain system, the recycled site watersystem, and their holding capacity. List all the plant species used. Include calcula-tions demonstrating that irrigation requirements can be met from captured rain orrecycled site water.
OR
❏ Provide the LEED Letter Template, signed by the landscape architect or respon-sible party, declaring that the project site does not have a permanent landscapeirrigation system. Include a narrative describing how the landscape design allowsfor this.
Summary of Referenced Standards
There is no standard referenced for this credit.
1 pointin addition to
WE 1.1
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Environmental Issues
Native landscapes that have lower irriga-tion requirements tend to attract nativewildlife, including birds, mammals andinsects, creating a building site that is in-tegrated with the natural surroundings.In addition, native plantings require lessfertilizer and fewer pesticides and, thus,reduce water quality impacts.
Economic Issues
Utility rates for potable water are expectedto escalate in future years as a result ofoverconsumption and finite potable wa-ter resources. Currently, the most effec-tive strategy to avoid escalating water costsis simply to use less potable water.
The cost of irrigation systems can be re-duced or eliminated through thoughtful ir-rigation planning. Although the cost formicro-irrigation systems is generally higherthan for conventional systems due to addi-tional design costs, the payback period canbe rapid due to lower water use and main-tenance requirements. Generally, micro-ir-rigation systems are comprised of fewer
materials, rely on less mechanical compo-nents for operation, and are easy to repairin the event of breakage.
Initial landscaping costs can be reduced ifthe existing plants on the site are retained.These plants are typically well-adapted tothe project site and reduce landscapingmaintenance costs due to minimal water,chemical and energy requirements.Xeriscapes or dry landscapes are another wayto reduce landscaping costs by eliminatingthe need for irrigation.
Community Issues
Water-efficient landscaping helps to con-serve local and regional potable water re-sources. Maintaining natural aquifer con-ditions is important to providing reliablewater sources for future generations.Consideration of water issues duringplanning can encourage developmentwhen resources can support it and pre-vent development if it exceeds the re-source capacity.
Design Approach
Strategies
Perform a soil and climate analysis to de-termine which plants will adapt best tothe site’s soil and climate, and specifyplants that are most suitable to site con-ditions. However, do not expect the re-sulting landscapes to require “no mainte-nance,” as nearly all landscapes requiresome routine upkeep. Therefore, com-pile and follow a seasonal maintenanceschedule for optimizing a healthy land-scape. This schedule should address spe-cific times for pruning, watering and pestinspection. In addition, use techniquessuch as integrated pest management,mulching, alternative mowing andcomposting to maintain plant health.These practices conserve water and helpfoster optimal soil conditions. Develop alandscaping water use baseline as de-scribed in the Calculations section.
Credit 1
Synergies
SS Prerequisite 1Erosion & SedimentationControl
SS Credit 1Site Selection
SS Credit 5Reduced SiteDisturbance
SS Credit 6Stormwater Management
SS Credit 7Landscape and ExteriorDesign to ReduceHeat Islands
WE Credit 3Water Use Reduction
EA Prerequisite 1Fundamental BuildingCommissioning
EA Prerequisite 2Minimum EnergyPerformance
EA Credit 1Optimize EnergyPerformance
EA Credit 3AdditionalCommissioning
EA Credit 5Measurement &Verification
EQ Prerequisite 1Minimum IAQPerformance
EQ Credit 7Thermal Comfort
EQ Credit 8Daylight & Views
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Design the site landscape with indigenousplants. Also specify and install a diver-sity of plants that are adapted to site con-ditions (climate, soils and natural wateravailability) and that do not need water-ing from municipal potable water afterestablishment. It is up to the landscapedesigner to provide documentation thatthe species selected will not require per-manent irrigation once established. Thegenerally accepted timeframe for tempo-rary irrigation is one to two years.
Specify and install a roof-water or ground-water collection system. Use metal, clayor concrete-based roofing materials andtake advantage of gravity water flowswhenever possible. Roofs made of asphaltor roofs with lead-containing materialscontaminate collected rainwater and ren-der it undesirable for reuse. The filtra-tion of collected rainwater for irrigationcan be achieved through a combinationof graded screens and paper filters. It isimportant to check local rainfall quantityand quality as collection systems may beinappropriate in areas with very low rain-fall. Also, rainwater that is highly acidicor has high mineral content may damagereuse systems. Conversely, rainwater mayhave a lower mineral content than thelocal water supply and may therefore beadvantageous for use in appliances suchas water heaters and washers.
Check with local health code departmentsfor guidelines regarding the collection ofrainwater, since such collection is not fed-erally regulated. If collected rainwater isto be used for potable or irrigation pur-poses, certain health code departmentsmight require back-flow prevention de-vices to avoid the risk of contaminatingpublic drinking water supplies.
Technologies
High-efficiency irrigation strategies includemicro-irrigation systems, moisture sensors,clock timers and weather database control-lers. These systems are widely available and
significantly more water-efficient than con-ventional irrigation systems.
Graywater systems can be used to recoverwater volumes from building sewage.Graywater consists of wastewater fromlavatories, showers, washing machines andother building activities that do not in-volve human waste or food processing.These graywater volumes can be storedin cisterns on the site and used in the irri-gation system. Also, stormwater volumescan be collected from hardscape surfaceson the site, such as roofing, and used inthe landscape irrigation system.
Synergies and Trade-Offs
Landscape design is highly dependent onthe site location and design. It may beadvantageous to couple the landscapedesign with water reuse strategies. Land-scape plantings may be designed to miti-gate climate conditions and reduce over-all energy consumption. Plants can be anatural aid to passive solar design, serveas windbreaks, and decrease noise. Irri-gation and water reuse schemes will af-fect building energy performance andtypically require commissioning and mea-surement & verification attention. High-efficiency irrigation systems do not workin the same manner as conventional irri-gation systems and it is important to un-derstand system operations. It is oftennecessary to train maintenance staff andto monitor regularly the irrigation systemto ensure that it is working properly. Thereuse of an existing building may dictatewater reuse strategies. Landscape designmay affect ventilation, daylighting andthermal comfort for the building.
Calculations
The following calculation methodologyis used to support the credit submittals aslisted on the first page of this credit. Inorder to quantify water-efficient landscap-ing measures, it is necessary to calculateirrigation volumes for the designed land-
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scape irrigation system for the month ofJuly and compare this with irrigation vol-umes required for a baseline landscapeirrigation system. The resulting watersavings is the difference between the twosystems. The factors that must be calcu-lated to determine irrigation volumes areexplained in detail in the following para-graphs and summarized in Table 1.
The Landscape Coefficient (KL) indi-
cates the volume of water lost via evapo-transpiration and is dependent on thelandscape species, the microclimate andthe planting density. The formula fordetermining the landscape coefficient isgiven in Equation 1.
The Species Factor (ks) accounts for varia-
tion of water needs by different plant spe-cies. The species factor can be divided intothree categories (high, average and low) de-pending on the plant species considered. Todetermine the appropriate category for aplant species, use plant manuals and pro-fessional experience. This factor is some-what subjective but landscape profession-als should have a general idea of the waterneeds of particular plant species. Land-scapes can be maintained in acceptable con-dition at about 50% of the reference evapo-transpiration (ET
0) value and thus, the av-
erage value of ks is 0.5. (Note: If a species
does not require irrigation once it is estab-lished, then the effective k
s = 0 and the re-
sulting KL = 0.)
The Density Factor (kd ) accounts for the
number of plants and the total leaf areaof a landscape. Sparsely planted areas willhave lower evapotranspiration rates thandensely planted areas. An average k
d is
applied to areas where ground shadingfrom trees is in the range of 60-100%.This is also equivalent to shrubs andground cover shading 90-100% of thelandscape area. Low k
d values are found
where ground shading from trees is lessthan 60% or shrub and groundcover isless than 90%. For instance, a 25%ground shading from trees results in a k
d
value of 0.5. In mixed landscape plantingswhere trees cover understory groundcoverand shrubs, evapotranspiration increases.This represents the highest level of land-scape density and the k
d value should be
between 1.0 and 1.3.
The Microclimate Factor (kmc
) accountsfor environmental conditions specific to thelandscape, including temperature, wind andhumidity. For instance, parking lot areasincrease wind and temperature effects onadjacent landscapes. The average k
mc is 1.0
and this refers to conditions where the land-scape evapotranspiration rate is unaffectedby buildings, pavements, reflective surfacesand slopes. Higher k
mc conditions occur
where evaporative potential is increased due
Table 1: Landscape Factors
Vegetation Type
low average high low average high low average high
Trees 0.2 0.5 0.9 0.5 1.0 1.3 0.5 1.0 1.4
Shrubs 0.2 0.5 0.7 0.5 1.0 1.1 0.5 1.0 1.3
Groundcovers 0.2 0.5 0.7 0.5 1.0 1.1 0.5 1.0 1.2
Mixed: trees, shrubs,groundcovers
0.2 0.5 0.9 0.6 1.1 1.3 0.5 1.0 1.4
Turfgrass 0.6 0.7 0.8 0.6 1.0 1.0 0.8 1.0 1.2
MicroclimateFactor (kmc)
SpeciesFactor (ks)
DensityFactor (kd)
Equation 1:
mcdsL kkkK ××=
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Table 2: Irrigation Types
Equation 2:
LL K]in[ET]in[ET ×= 0
Irrigation Type IE
Sprinkler 0.625
Drip 0.90
to landscapes surrounded by heat-absorb-ing and reflective surfaces or are exposed toparticularly windy conditions. Examplesof high k
mc areas include parking lots, west
sides of buildings, west and south sides ofslopes, medians, and areas experiencingwind tunnel effects. Low microclimate ar-eas include shaded areas and areas protectedfrom wind. North sides of buildings, court-yards, areas under wide building overhangs,and north sides of slopes are low microcli-mate areas. Table 1 provides suggested val-ues for k
s, k
mc, and k
d.
Once KL is determined, the evapotrans-
piration (ET) rate of the specific landscape(ET
L) can be calculated. K
L is multiplied
by the reference evapotranspiration(ET
0 ) to obtain ET
L as shown in Equa-
tion 2. The evapotranspiration rate isa measurement of the total amount ofwater needed to grow plants and crops.Different plants have different waterneeds, and thus different ET rates. Irri-gation calculations are simplified by us-ing ET
0, which is an average rate for a
known surface, such as grass or alfalfa,used as a reference point and expressed inmillimeters or inches.
The values for ET0 in various regions
throughout the United States can befound in regional agricultural data (seeResources section). The ET
0 for July is
used in the LEED calculation because thisis typically the month with the greatestevapotranspiration effects and, therefore,the greatest irrigation demands.
To calculate irrigation volumes, apply theirrigation efficiency (IE). Table 2 listsirrigation efficiencies for sprinkler anddrip irrigation systems.
The Total Potable Water Applied(TPWA) to a given area (A) is calculatedin Equation 3.
This equation indicates that a smallerlandscape area, a smaller ET
L value, and
a larger IE value result in a lower TPWAvalue. This is sensible because smaller
landscape areas require less water to irri-gate, a smaller ET
L value means less wa-
ter loss due to evapotranspiration, and ahigher IE means that irrigation water isbeing used more efficiently.
To determine the water savings for thedesigned landscaping irrigation system,perform the above calculations for thedesign case as well as a baseline case.
1. Use Table 1 to determine the appro-priate landscape factors for each specificlandscape area in the design case (e.g., k
s,
kmc
, and kd ). Use a spreadsheet to sum-
marize the different landscape areas andthe associated factors.
2. Calculate the landscape coefficient(K
L ) for each landscape area using the ap-
propriate landscape factors and Equation 1.
3. Calculate the specific landscape evapo-transpiration rate (ET
L) of each landscape
area using the corresponding landscapecoefficient (K
L) and the ET
L formula in
Equation 2.
4. Calculate the TPWA to each landscapearea using Equation 3 and the applicablesurface area, specific landscape evapotrans-piration rate and irrigation efficiency data.
Repeat the above steps for the baseline caseusing conventional plant species and plantdensities as determined by the project’s land-scape consultant. Differences between thetwo cases result from plant species choices,plant densities and irrigation system choices.Planting types should approximately cor-respond in both the baseline and designcases (i.e., it is unreasonable to assume that
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Equation 3:
IE
]in[ET]SF[A]gal[TPWA
L×=
the baseline is 100% turfgrass if a projectclearly intends to include trees, shrubs andplanting beds). Do not change the land-scape areas, microclimate factors or refer-ence evapotranspiration rates.
An example of irrigation calculations ispresented below. An office building inAustin, Texas, has a total site area of 6,000square feet. The site consists of three land-scape types: groundcover, mixed vegeta-tion and turf grass. All of the site areasare irrigated with a combination of po-table water and graywater harvested fromthe building. The reference evapotrans-piration rate (ET
0) for Austin in July was
obtained from the local agricultural dataservice and is equal to 8.12.
The high-efficiency landscape irrigationcase utilizes drip irrigation with an effi-ciency of 90% and reuses an estimated9,000 gallons of graywater during themonth of July. Table 3 shows the calcu-
lations to determine potable water use forthe design case.
The baseline case uses the same referenceevapotranspiration rate and total site area.However, the baseline case uses sprinklersfor irrigation (IE = 0.625), does not takeadvantage of graywater harvesting, and usesonly shrubs and turf grass. Calculations todetermine potable water use for the baselinecase are presented in Table 4.
The example illustrates that the designcase has an irrigation water demand of23,474 gallons. Graywater reuse provides4,200 gallons towards the demand, andthis volume is treated as a credit in thewater calculation. Thus, the total potablewater applied to the design case in July is19,274 gallons. The baseline case has anirrigation demand of 62,518 gallons andreuses no graywater. The difference be-tween the two cases results in potablewater savings of 69% for the design case.
It is important to note that the LEEDcalculation provides an indication of thegeneral efficiency gains provided by thegreen design. For more accurate under-
Area KL ETL TPWA
[SF] [gal]
1,200 Low 0.2 Avg 1.0 High 1.3 0.3 2.11 2,815
3,900 Low 0.2 Avg 1.1 High 1.4 0.3 2.50 10,837
900 Avg 0.7 Avg 1.0 High 1.2 0.8 6.82 9,822
Subtotal [gal] 23,474
July Graywater Harvest [gal] (4,200)
Net GPWA [gal] 19,274
Area KL ETL TPWA
[SF] [gal]
1,200 Avg 0.5 Avg 1.0 High 1.3 0.7 5.28 10,134
4,800 Avg 0.7 Avg 1.0 High 1.2 0.8 6.82 52,384
62,518
Drip
Drip
Shrubs
Mixed
Turfgrass
Shrubs
Sprinkler
Sprinkler
SprinklerTurfgrass
IESpecies
FactorDensityFactor
Microclimate Factor
(kmc)
(ks) (kd) (kmc)
Landscape
Type
Landscape
Type
SpeciesFactor
Net GPWA [gal]
Microclimate Factor
(kd)(ks)
DensityFactor
IE
Table 3: Design Case (July)
Table 4: Baseline Case (July)
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standing of water use and efficiency op-portunities, an annual water balance isrequired. For example, graywater volumesmay or may not be consistently availablethroughout the year because these vol-umes are dependent on building occupantactivities. In a typical office building,graywater volumes will change slightlydue to vacation schedules and holidaysbut should be relatively consistent overthe year. In contrast, graywater volumesin a school building will substantially de-crease in summer months as a result ofreduced building occupancy, and, there-fore, graywater volumes may not be avail-able for irrigation. Graywater systemsshould be modeled to predict graywatervolumes generated on a monthly basis aswell as optimal storage capacity of thegraywater system. It is also important toaddress possible treatment processesneeded for reuse and design of a makeupwater system if graywater volume is notsufficient to satisfy reuse demands.
Rain harvest volume depends on theamount of precipitation that the projectsite experiences and the rainwater collec-tion surface’s area and efficiency. SeeEquation 4 and consult a rainwater har-vesting guide for more detailed instruc-tion. Rainfall data is available from thelocal weather service (see the Resourcessection). Within the credit calculations,project teams may either use the collectedrainwater total for July based on histori-cal average precipitation, or use the his-torical data for each month in order tomodel collection and reuse throughoutthe year. The latter method allows theproject team to determine what volumeof water is expected to be in the storagecistern at the beginning of July and addit to the expected rainwater volume col-lected during the month. This approach
also allows the project team to determinethe optimal size of the rainwater cistern.
Resources
Web Sites
American Rainwater Catchment Sys-tems Association
www.arcsa-usa.org
Includes a compilation of publications,such as the Texas Guide to Rainwater Har-vesting.
A Guide to Estimating Irrigation Needsof Landscape Plantings
w w w. o w u e . w a t e r . c a . g o v / d o c s /wucols00.pdf, (916) 653-1097
Provides detailed methodology for calcu-lating irrigation needs for a wide varietyof landscape types. Also includes specificdata for California climates.
A nonprofit organization focused on pro-moting products for the efficient use ofwater for irrigation applications. Thisspecific Web link is for evapotranspira-tion data contacts for each U.S. state.
National Climatic Data Center
www.ncdc .noaa .gov /oa /c l imate /stateclimatologists.html
Useful for researching local climate data,such as rainfall data for rainwater harvest-ing calculations. Includes links to stateclimate offices.
Native Plant Societies
Your state or regional native plant societyis an excellent resource for identifying cli-mate-appropriate vegetation.
Equation 4:
Rainwater Volume [gal] = collection area [SF] x collection efficiency [%] x average rainfall [in] x 0.6233 gal/in
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Texas Evapotranspiration Web Site
texaset.tamu.edu/index.php
An evapotranspiration data Web site forthe State of Texas with a discussion ofevapotranspiration and sprinkler efficien-cies.
U.S. Department of the Interior – Bu-reau of Reclamation
www.usbr.gov/main/water
The Bureau’s Agrimet Data System pro-vides evapotranspiration rates for severalregions in the U.S.
WaterWiser: The Water EfficiencyClearinghouse
www.waterwiser.org, (800) 926-7337
A Web clearinghouse with articles, refer-ence materials and papers on all forms ofwater efficiency.
A Web site that has general descriptionsand strategies for water efficiency in gar-dens and landscapes.
Print Media
ASCE Manuals and Reports on Engi-neering Practice No. 70, “Evapotrans-piration and Irrigation Water Require-ments,” ASCE, 1990.
Estimating Water Requirements ofLandscape Plantings, University of Cali-fornia Cooperative Extension, Division ofAgriculture and Natural Resources, Leaf-let 21493.
Landscape Irrigation: Design and Man-agement, by Stephen W. Smith, JohnWiley and Sons, 1996.
Turf Irrigation Manual, Fifth Edition,by Richard B. Choate, Telsco Industries,1994.
Definitions
Blackwater is wastewater from toilets andkitchen sinks that contains organic ma-terials.
Drip Irrigation is a high-efficiency irriga-tion method in which water drips to thesoil from perforated tubes or emitters.
Evapotranspiration is the loss of waterby evaporation from the soil and transpi-ration from plants.
Graywater is wastewater from lavatories,showers, bathtubs, washing machines andsinks that are not used for disposal of haz-ardous or toxic ingredients or wastes fromfood preparation.
Potable Water is water that is suitable fordrinking and is supplied from wells ormunicipal water systems.
Xeriscape or “dry landscape” designsadopt water conservation as the primaryobjective. Xeriscape landscapes are basedon sound horticultural practices and in-corporate native plant species that areadapted to local climate conditions.
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Case Study
Monsanto Company Life Sciences IncubatorSt Louis, Missouri
The Monsanto Company Life Sciences Incubator building is aLEED Version 1.0 Silver Pilot Project that houses research facili-ties committed to finding solutions to growing global needs forfood and health. The building design was inspired by a circularstone Shaker barn in New England and includes two above-groundcisterns to harvest rainwater volumes from the roof for landscapeirrigation. Rainwater is collected via a passive gravity-fed collec-tion system and up to 12,000 gallons of water can be stored inthe cisterns. This water is then applied manually to the land-scape as needed, saving an estimated 28,000 gallons of potablewater annually.
OwnerMonsanto Company
Courtesy of Monsanto Company
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Credit 2Innovative Wastewater Technologies
Intent
Reduce generation of wastewater and potable water demand, while increasing the localaquifer recharge.
Requirements
Reduce the use of municipally provided potable water for building sewage conveyanceby a minimum of 50%, OR treat 100% of wastewater on site to tertiary standards.
Submittals
❏ Provide the LEED Letter Template, signed by the architect, MEP engineer orresponsible party, declaring that water for building sewage conveyance will be re-duced by at least 50%. Include the spreadsheet calculation and a narrative demon-strating the measures used to reduce wastewater by at least 50% from baselineconditions.
OR
❏ Provide the LEED Letter Template, signed by the civil engineer or responsibleparty, declaring that 100% of wastewater will be treated to tertiary standards onsite. Include a narrative describing the on-site wastewater treatment system.
Summary of Referenced Standard
There is no standard referenced for this credit.
1 point
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Once wastewater has been conveyed totreatment facilities, extensive treatment isrequired to remove contaminants beforedischarging to a receiving water body. Amore efficient method for handling waste-water is to treat it on-site. On-site waste-water strategies reduce regional wastewa-ter infrastructure costs as well as provideautonomy from the public treatmentworks. A variety of on-site wastewatertreatment options are available includingconventional biological treatment facili-ties similar to regional treatment plantsand “living machine” systems that mimicnatural processes to treat wastewater.
Environmental Issues
On-site wastewater treatment systemstransform perceived “wastes” into re-sources that can be used on the buildingsite. These resources include treated wa-ter volumes for potable and non-potableuse, as well as nutrients that can be ap-plied to the site to improve soil condi-tions. Reducing wastewater treatment atthe local wastewater treatment worksminimizes public infrastructure, energyuse and chemical use. In rural areas, on-site wastewater treatment systems avoidaquifer contamination problems prevalentin current septic system technology.
Economic Issues
Commercial and industrial facilities thatgenerate large amounts of wastewater canrealize considerable savings by recyclinggraywater. For example, carwashes andtruck maintenance facilities generate largevolumes of graywater that can be effectivelytreated and reused. Often, a separate tank,filter and special emitters are necessary fora graywater irrigation system. The dualplumbing lines installed during initial con-struction will approximately double the costof plumbing. However, water storage is thehighest cost in any rainwater collection sys-tem, much greater than costs for the catch-ment area, water conveyance, filtration anddistribution components. Storage tanks andcisterns in a variety of sizes and materialsare regionally available. In some systems,there are additional energy costs requiredfor operation.
Water recovery systems are most cost-effec-tive in areas where there is no municipalwater supply, where the developed wells areunreliable, or if well water requires treat-ment. Collecting and using rainwater orother site water volumes reduces site runoffand the need for runoff devices. It alsominimizes the need for utility-providedwater, thus reducing some initial and oper-ating costs. In some areas with a decentral-ized population, collection of rainwater of-fers a low-cost alternative to a central pipedwater supply.
Wastewater treatment systems and waterrecovery systems involve an initial capitalinvestment in addition to the mainte-nance requirements over the building’slifetime. These costs must balance withthe anticipated savings in water and sewerbills. This savings can minimize theamount of potable water that a munici-pality must provide, thereby leading tomore stable water rates.
A constructed wetland for wastewatertreatment can add value to a developmentas a site enhancement. Wetlands are ben-eficial because they provide flood protec-
Credit 2
Synergies
SS Credit 1Site Selection
SS Credit 5Reduced SiteDisturbance
SS Credit 6StormwaterManagement
WE Credit 3Water Use Reduction
EA Prerequisite 1Fundamental BuildingSystems Commissioning
EA Prerequisite 2Minimum EnergyPerformance
EA Credit 1Optimize EnergyPerformance
EA Credit 3AdditionalCommissioning
EA Credit 5Measurement &Verification
MR Credit 1Building Reuse
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tion and stabilize soils on site. Currently,packaged biological wastewater systemshave an initial high cost relative to theoverall building cost due to the noveltyof the technology.
Community Benefits
By reducing potable water use, the localaquifer is conserved as a water resourcefor future generations. In areas whereaquifers cannot meet the needs of thepopulation economically, rainwater andother recovered water is the least expen-sive alternative source of water. Reserv-ing potable water only for specific appli-cations benefits the entire communitythrough lower utility rates and taxes.
Design Approach
Strategies
Develop a wastewater inventory and de-termine areas where graywater can be usedfor functions that are conventionallyserved by potable water. These functionsmight include sinks, showers, toilets,landscape irrigation, industrial applica-tions and custodial applications. Alsoestimate the demand for these applica-tions and the availability of graywater gen-erated on the site. Finally, determine theamount of wastewater that will requiretreatment and select the most suitabletreatment strategy.
Potable water is used for many functionsthat do not require high-quality water.Graywater systems reuse the wastewaterfrom sinks, showers and other sources forthe flushing of toilets, landscape irriga-tion, and other functions that do not re-quire potable water. Roof-water orgroundwater collection systems harvestwater that otherwise would be absorbedinto the ground or released to local waterbodies. If it is likely that a graywater sys-tem will be used in the future, install dualplumbing lines during the initial con-struction to avoid the substantial costs anddifficulty in adding them later.
Figure 1 depicts an example design forrain harvesting reuse. Precipitation vol-umes are captured on the roof and trans-ported to a basement storage tank viagutters and downspouts. The basementstorage tank has an overflow device if thevolume of runoff exceeds capacity andpotable water makeup (***device?) if therunoff volume is less than the minimumvolume required for reuse. The runoffvolumes are then filtered and pumped towater closets and washing machines in thebuilding as needed.
Check with the local health departmentfor regulations governing the use of agraywater system and the permits re-quired. Each state has its own standardsfor graywater irrigation systems. Texasand California, for example, have stan-dards that encourage the use of graywatersystems. Other states have regulationsthat may limit or prohibit graywater use.In many areas, irrigation with graywatermust be subsurface, although some re-gions allow above-ground irrigation.
Consider an on-site wastewater treatmentsystem such as constructed wetlands, amechanical recirculating sand filter, or anaerobic biological treatment reactor.
Technologies
The construction of artificial wetlands forwastewater treatment can be incorporatedon multiple scales to accommodateprojects ranging from individual build-ings to larger developments. As waste-water moves through the wetlands or bod-ies of water, plants and microbes natu-rally remove water contaminants. An-other technology involves creating anaquaculture system, where contaminantsin the wastewater become food for fishand plants.
Remember to check with local healthcode departments regarding current regu-lations governing the use of biologicalwastewater systems. Most require permitsfor these systems. Regularly scheduled
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maintenance on these systems will in-crease their lifetimes and reduce opera-tions problems. An EPA study found thatecological systems are comparable in costto conventional wastewater treatmentonly for volumes of 50,000 gallons perday or less. An aquaculture system is usu-ally a high-cost and high-maintenancesystem, yet it can yield food and fertilizerin return.
Modular wastewater treatment systemscan be purchased to remove wastewatercontaminants including TSS and TP.Some systems imitate natural ecosystemsto treat wastewater volumes biologicallywhile other systems are designed withphysical, chemical and biological tech-nologies similar to publicly owned treat-ment works. Both types of systems pro-
duce effluents that can be used for non-potable applications such as irrigation andtoilet flushing.
Synergies and Trade-Offs
The necessity and availability of waste-water reuse and treatment strategies isheavily influenced by the building loca-tion. In remote locations, it may be cost-effective to use an on-site wastewater treat-ment system.
Conversely, a project located in a densearea with little site area, and with limitedwastewater treatment, graywater orstormwater reuse facilities, may not beable to capture this credit. This credithas close ties to water efficiency effortsbecause a greater amount of potable wa-ter saved often results in less blackwater
Rain Harvest
Scuppers
Rain Leader
Low Flow
Fixutures
Lifting Pump
Storage Tank
Potable Supply
Figure 1: An Illustration of a Rain Harvesting System
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Equation 1:
Equation 3:
Equation 2:
]flushor[minUse
]gal[VolumeWater]flushesors[minDurationUses]gal[
SewageVolume
××=
]gal[SewageFemale
GenerationFemale
Occupants]gal[
SewageMaleGeneration
MaleOccupants
]gal[SewageDaily
Generation×+×=
]days[Workdaysday
galSewageTotalGeneration
]gal[SewageAnnual
Generation×
=
generated. For instance, water efficientwater closet and urinal fixtures not onlyreduce potable water demand but alsoreduce blackwater volumes created. Thus,performance results will often overlapwith those of WE Credit 3.
Energy use may be needed for treatmentplant operation or for reuse strategies.These systems also require commission-ing and measurement & verification at-tention. Reuse of an existing buildingcould hinder adoption of an on-site waste-water treatment facility.
Calculations
The following calculation methodology isused to support the credit submittals listedon the first page of this credit. Wastewatercalculations are based on the annual gen-eration of blackwater volumes from plumb-ing fixtures such as water closets and uri-nals. The calculations compare the designcase with a baseline case. The steps to cal-culate the design case are as follows:
1. Create a spreadsheet listing each typeof blackwater-generating fixture and fre-quency of use data. Frequency-of-use dataincludes the number of female and maledaily uses, and the sewage generated peruse. Using these values, calculate the to-tal sewage generated for each fixture typeand gender (see Equation 1).
2. Sum all of the sewage generation volumesused for each fixture type to obtain male andfemale daily sewage generation volumes.
3. Multiply the male and female sewagegeneration volumes by the number ofmale and female building occupants andsum these volumes to obtain the dailytotal sewage generation volume (seeEquation 2).
4. Multiply the total daily sewage volumeby the number of workdays in a typicalyear to obtain the total annual sewagegeneration volume for the building (seeEquation 3).
5. If rainwater harvest or graywater reusestrategies are employed in the building,subtract these annual volumes from theannual sewage generation volume. The re-sult shows how much potable water isused for sewage conveyance annually.
Repeat the above calculation methodol-ogy for the baseline case. Use EnergyPolicy Act of 1992 fixture flow rates forthe baseline case (see WE Credit 3, Table1). Do not change the number of build-ing occupants, the number of workdays,or the frequency data. Do not includegraywater or rainwater harvest volumes.
Table 1 shows example potable watercalculations for sewage conveyance for atwo-story office building with a capacityof 300 occupants. The calculations arebased on a typical 8-hour workday. It isassumed that building occupants are 50%male and 50% female. Male occupantsare assumed to use water closets once andurinals twice in a typical work day. Fe-
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Table 1: Design Case
Daily
UsesFlowrate Occupants
Sewage Generation
[GPF] [gal]
0 1.1 150 0
3 1.1 150 495
1 0.0 150 0
0 0.0 150 0
2 0.0 150 0
0 0.0 150 0
Total Daily Volume [gal] 495
Annual Work Days 260
Annual Volume [gal] 128,700
Rainwater or Graywater Reuse Volume [gal] (36,000)
TOTAL ANNUAL VOLUME [gal] 92,700
Waterless Urinal (Female)
Fixture Type
Composting Toilet (Male)
Low-Flow Water Closet (Male)
Low-Flow Water Closet (Female)
Composting Toilet (Female)
Waterless Urinal (Male)
male occupants are assumed to use waterclosets three times.
First, the design case is considered to de-termine annual potable water usage forsewage conveyance. The designed build-ing has fixtures that use non-potable wa-ter for sewage conveyance (i.e., rainwa-ter) or no water for sewage conveyance(i.e., waterless urinals and compostingtoilets). Table 1 summarizes the sewagegeneration rates and indicates that 92,700gallons of potable water are used annu-ally for sewage conveyance.
When using graywater and rainwatervolumes, calculations are required todemonstrate that these reuse volumes aresufficient to meet water closet demands.These quantities are then subtractedfrom the gross daily total because theyreduce potable water usage. In the ex-ample, 36,000 gallons of rainwater areharvested and directed to water closetsfor flushing.
Next, the baseline potable water usage forsewage conveyance is developed usingconventional fixtures that comply withthe Energy Policy Act of 1992. Toiletsare 1.6 gallons per flush (GPF) and uri-
nals are 1.0 GPF. All fixtures drain to theexisting municipal sewer system.
Table 2 provides a summary of baselinecalculations. The baseline case estimatesthat 327,600 gallons of potable water peryear for sewage conveyance.
Comparison of the baseline to the de-signed building indicates that a 72% re-duction in potable water volumes used forsewage conveyance is realized (1 – 92,700/327,600). Thus, this strategy earns onepoint for this credit. When developingthe baseline, only the fixtures, sewage gen-eration rates and the water reuse creditare different from the designed building.Usage rates, occupancy and number ofworkdays are identical for the designedcase and the baseline case. See Table 3for sample fixture flow rates.
When reusing graywater volumes fromthe building, it is necessary to model thesystem on an annual basis to determinegraywater volumes, generated storage ca-pacity of the system and any necessarytreatment processes before reusing thewater volumes. Graywater volumes mayor may not be consistently availablethroughout the year because these vol-
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Table 2: Baseline Case
Table 3: Sample Fixture Types and GPFs
Daily
Uses
Flowrate OccupantsSewage
Generation
[GPF] [gal]
1 1.6 150 240
3 1.6 150 720
2 1.0 150 300
0 1.0 150 0
Total Daily Volume [gal] 1,260
Annual Work Days 260
TOTAL ANNUAL VOLUME [gal] 327,600
Fixture Type
Urinal (Male)
Water Closet (Male)
Water Closet (Female)
Urinal (Female)
Fixture Type [GPF]
Conventional Water Closet 1.6
Low-Flow Water Closet 1.1
Ultra Low-Flow Water Closet 0.8
Composting Toilet 0.0
Conventional Urinal 1.0
Waterless Urinal 0.0
umes are dependent on building occupantactivities. For instance, in a typical officebuilding, graywater volumes will changeslightly due to vacation schedules andholidays but should be relatively consis-tent over the year.
In contrast, graywater volumes in a schoolbuilding will substantially decrease insummer months due to the school calen-dar, and, therefore, graywater volumesmay not be available for irrigation.
If the project uses rainwater volume as asubstitute for potable volumes in waterclosets or urinals, it is necessary to calcu-late water savings over a time period ofone year. Rain harvest volume depends
on the amount of precipitation that theproject site experiences and the rainwatercollection surface’s area and efficiency. SeeEquation 4 and consult a rainwater har-vesting guide for more detailed instruc-tion. Rainfall data is available from thelocal weather service (see the Resourcessection). Rainwater volume depends onvariations in precipitation, and, thus, it isnecessary to model the reuse strategy onan annual basis. A model of rainwatercapture based on daily precipitation andoccupant demand is helpful to determinethe rainwater volumes captured and stor-age tank size. Subtract annual rainwateruse for sewage conveyance in the designcase calculations.
Resources
Web Sites
American Rainwater Catchment Sys-tems Association
www.arcsa-usa.org
Includes a compilation of publications,such as the Texas Guide to Rainwater Har-vesting.
Rainwater Volume [gal] = collection area [SF] x collection efficiency [%] x average rainfall [in] x 0.6233 gal/in
Equation 4:
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How to Conserve Water and Use itWisely
www.epa.gov/OW/you/chap3.html
A U.S. EPA document that provides guid-ance for commercial, industrial and resi-dential water users on saving water andreducing sewage volumes.
National Climatic Data Center
www.ncdc .noaa .gov /oa /c l imate /stateclimatologists.html
Useful for researching local climate data,such as rainfall data for rainwater harvest-ing calculations. Includes links to stateclimate offices.
Print Media
Constructed Wetlands for WastewaterTreatment and Wildlife Habitat: 17Case Studies, EPA 832/B-93-005, 1993.
Mechanical & Electrical Equipment forBuildings, Eighth Edition, by BenjaminStein and John Reynolds, John Wiley andSons, 1992.
Sustainable Building TechnicalManual, Public Technology, Inc., 1996(www.pti.org).
Definitions
Aquatic Systems are ecologically de-signed treatment systems that utilize adiverse community of biological organ-isms (e.g., bacteria, plants and fish) totreat wastewater to advanced levels.
On-Site Wastewater Treatment uses lo-calized treatment systems to transport,store, treat and dispose of wastewater vol-umes generated on the project site.
Potable Water is defined as water thatmeets drinking water quality standardsand is approved for human consumptionby the state or local authorities havingjurisdiction.
Tertiary Treatment is the highest formof wastewater treatment and includes re-moval of organics, solids and nutrients aswell as biological or chemical polishing,generally to effluent limits of 10 mg/LBOD
5 and 10 mg/L TSS.
Also see WE Credit 1 definitions.
Case Study
C.K. Choi Building for the Institute of Asian ResearchVancouver, British Columbia
The C.K. Choi Building for the Institute of Asian Research atthe University of British Columbia is a campus research build-ing. The building incorporates two strategies to reduce wastewa-ter generation. All toilets in the building are composting toiletsthat function without water and transform human wastes intocompost that can be applied to the site landscape. Liquid wastesfrom the composting toilets and other building sources (lavato-ries, kitchen sinks and urinals) are directed through a simulatedwetland system. This system doubles as a landscape feature nextto the building and treats the liquid wastes before application tothe site landscape. These strategies allow for the building to bedisconnected from the existing sanitary sewer infrastructure.
OwnerUniversity of British Columbia
Courtesy of Paladino Consulting LLC
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Credit 3.1Water Use Reduction20% Reduction
Intent
Maximize water efficiency within buildings to reduce the burden on municipal watersupply and wastewater systems.
Requirements
Employ strategies that in aggregate use 20% less water than the water use baselinecalculated for the building (not including irrigation) after meeting the Energy PolicyAct of 1992 fixture performance requirements.
Submittals
❏ Provide the LEED Letter Template, signed by the MEP engineer or responsibleparty, declaring that the project uses 20% less water than the baseline fixture per-formance requirements of the Energy Policy Act of 1992.
❏ Provide the spreadsheet calculation demonstrating that water-consuming fixturesspecified for the stated occupancy and use of the building reduce occupancy-basedpotable water consumption by 20% compared to baseline conditions.
1 point
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Credit 3.2 Water Use Reduction30% Reduction
Intent
Maximize water efficiency within buildings to reduce the burden on municipal watersupply and wastewater systems.
Requirements
Employ strategies that in aggregate use 30% less water than the water use baselinecalculated for the building (not including irrigation) after meeting the Energy PolicyAct of 1992 fixture performance requirements.
Submittals
❏ Provide the LEED Letter Template, signed by the MEP engineer or responsibleparty, declaring that the project uses 30% less water than the baseline fixture per-formance requirements of the Energy Policy Act of 1992.
❏ Provide the spreadsheet calculation demonstrating that water-consuming fixturesspecified for the stated occupancy and use of the building reduce occupancy-basedpotable water consumption by 30% compared to baseline conditions.
Summary of Referenced Standard
The Energy Policy Act (EPAct) of 1992
This Act was promulgated by the U.S. government and addresses energy and wateruse in commercial, institutional and residential facilities. The water usage require-ments of the Energy Policy Act of 1992 are provided in Table 1.
Table 1: EPACT Fixture Ratings
FixtureEnergy Policy Act of 1992
Flow Requirement
Water Closets [GPF] 1.6
Urinals [GPF] 1.0
Showerheads [GPM]* 2.5
Faucets [GPF]* 2.5
Replacement Aerators [GPM]* 2.5
Metering Faucets [gal/CY] 0.25
*At flowing water pressure of 80 pounds per square inch (psi)
1 pointin addition to
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Credit 3Green Building ConcernsThe Energy Policy Act of 1992 establishedwater conservation standards for waterclosets, shower heads, faucets and otheruses to save the United States an estimated6.5 billion gallons of water per day. Toi-let flushing uses the most water in resi-dential and commercial buildings, ac-counting for approximately 4.8 billiongallons per day. Older toilets use 4 to 8gallons of water per flush, while all newtoilets must have a maximum flush vol-ume of 1.6 gallons.
While the EPAct is a good starting point,there are many ways to exceed this stan-dard and achieve even greater water sav-ings. Effective methods to reduce potablewater use include reusing roof runoff vol-umes for non-potable applications, in-stalling sensors and flow restrictors onwater fixtures, and installing dry fixturessuch as composting toilets and waterlessurinals.
Environmental Issues
The reduction of potable water use inbuildings for toilets, shower heads andfaucets reduces the total amount with-drawn from rivers, streams, undergroundaquifers and other water bodies. Anotherbenefit of potable water conservation isreduced energy use and chemical inputsat municipal water treatment works.
Economic Issues
Reductions in water consumption mini-mize overall building operating costs. Re-ductions can also lead to more stablemunicipal taxes and water rates. By han-dling reduced water volumes, water treat-ment facilities can delay expansion andmaintain stable water prices.
Accelerated installation of high-efficiencyplumbing fixtures, especially 1.6 gallonper flush (GPF) toilets, through incen-tive programs has become a cost-effectiveway for some municipalities to defer, re-
duce or avoid capital costs of needed wa-ter supply and wastewater facilities.
For example, New York City invested$393 million in a 1.6 GPF toilet-rebateprogram that has reduced water demandand wastewater flow by 90.6 million gal-lons per day (MGD), equal to 7% of thecity’s total water consumption. The rebateprogram accomplished a net present valuesavings of $605 million from a 20-yeardeferral of water supply and wastewatertreatment expansion projects. Anothersuccessful water efficiency program wasinstituted in Santa Monica, where thetoilet replacement program achieved per-manent reductions in water usage andwastewater flows of over 1.9 MGD, rep-resenting a 15% reduction in average to-tal water demand and a 20% reductionof average total wastewater flow. The costof the rebate program was $5.4 million.The program will have a net savings of$6 million in the year 2002 due to avoidedcosts of water imports and wastewatertreatment.
Water-conserving fixtures that use lesswater than requirements in the EnergyPolicy Act of 1992 may have higher ini-tial costs. Additionally, there may be alonger lead time for delivery because oftheir limited availability.
The first cost of composting toilets is sig-nificantly higher than conventional wa-ter closets and they may initially requireadditional maintenance attention. Somecomposting toilets also carry an ongoingenergy cost to run fans and other systemequipment. Nonetheless, significant op-erational savings are realized througheliminated potable water use and sewagegeneration.
Community Issues
Water use reductions, in aggregate, allowmunicipalities to reduce or defer the capi-tal investment needed for water supplyand wastewater treatment infrastructure.These strategies protect the natural water
Synergies
SS Credit 1Site Selection
SS Credit 5Reduced SiteDisturbance
SS Credit 6StormwaterManagement
WE Credit 1Water EfficientLandscaping
WE Credit 2Innovative WastewaterTechnologies
EA Prerequisite 1Fundamental BuildingSystems Commissioning
EA Prerequisite 2Minimum EnergyPerformance
EA Credit 1Optimize EnergyPerformance
EA Credit 3AdditionalCommissioning
EA Credit 5Measurement &Verification
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cycle and save water resources for futuregenerations.
Design Approach
Strategies
Develop a water use inventory that in-cludes all water-consuming fixtures,equipment and seasonal conditions ac-cording to the methodology outlined inthe Calculations section. Consider de-veloping the inventory in conjunctionwith WE Credit 2. Use this to identifysignificant potable water demands anddetermine methods to minimize or elimi-nate these demands.
Specify water-conserving plumbing fix-tures that exceed the fixture requirementsstated in the Energy Policy Act of 1992.Consider ultra-high efficiency fixture andcontrol technologies, including toilets,faucets, showers, dishwashers, clotheswashers and cooling towers. A variety oflow-flow plumbing fixtures and appli-ances are currently available in the mar-ketplace and can be installed in the samemanner as conventional fixtures.
Technologies
Water-efficient shower heads are availablethat require less than 2.5 GPM. Bath-room faucets are typically used only forwetting purposes and can be effective withas little as 1.0 GPM. Water-saving faucetaerators can be installed that do notchange the feel of the water flow. Specifyself-closing, slow-closing or electronic sen-sor faucets, particularly in high-use pub-lic areas where it is likely that faucets maybe carelessly left running.
Water closets are a significant user of po-table water. There are a number of toi-lets that use considerably less than 1.6GPF, including pressure-assisted toiletsand dual flush toilets that have an optionof 0.8 GPF or 1.0 GPF. Unfortunately,it is currently difficult to obtain these fix-tures in North America.
Consider dry fixtures such as waterless uri-nals and composting toilets. These tech-nologies use no water volumes to copewith human waste. Waterless urinals useadvanced hydraulic design and a buoy-ant fluid instead of water to maintain sani-tary conditions. Composting toilets mixhuman waste with organic material toproduce a nearly odorless end productthat can be used as a soil amendment.These fixtures have been used successfullybut to a limited extent in commercial set-tings. Composting toilets may not beacceptable by health code departments insome areas, and, thus, it is important tocheck with the local health code depart-ment to uncover regulations governingthe use of both composting toilets andwaterless urinals. Also, if the buildingallows for public access to restroom fa-cilities, it is important to educate usersabout system operation and purpose.Signage in restrooms is a good way toeducate users, and signs should includeinstructions and a brief description of howthe system functions. This is especiallytrue for composting toilets that do notfunction in the same manner as conven-tional water closets.
Consider specifying water-efficient cool-ing towers that use delimiters to reducedrift and evaporation. Couple coolingtowers with water recovery systems tooperate with graywater or stormwatervolumes. However, keep in mind thatdelimiters may require larger fans in thecooling tower system, resulting in in-creased energy use.
Synergies and Trade-Offs
Water use strategies depend on the sitelocation and site design. Project sites withno access to municipal potable water ser-vice typically use groundwater wells tosatisfy potable water demands. Sites withsignificant precipitation volumes maydetermine that reuse of these volumes ismore cost-effective than creatingstormwater treatment facilities. Potable
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water use is significant for irrigation ap-plications and is directly correlated withthe amount of wastewater generated on-site. Strategies and performance resultsmay overlap with those of WE Credit 2.
Some water-saving technologies impactenergy performance and require commis-sioning and measurement & verificationattention. Reuse of existing buildings mayhinder water efficiency measures due tospace constraints or existence of plumb-ing fixtures.
Calculations
The following calculation methodologyis used to support the credit submittalslisted on the first page of this credit. Tocalculate the potable water savings for abuilding, the design case must be com-pared with a baseline case. The steps tocalculate the design case are as follows:
1. Create a spreadsheet listing each wa-ter-using fixture and frequency-of-usedata. Frequency-of-use data includes thenumber of female and male daily uses, theduration of use, and the water volume peruse. There are no set criteria for deter-mining daily use or duration of use. Ap-plicants can estimate both of these itemsbased on the project’s program require-ments. With these values, calculate thetotal potable water used for each fixturetype and gender (see Equation 1).
2. Sum all of the water volumes used foreach fixture type to obtain male and fe-
male total daily potable water use.
3. Multiply male and female potable wa-ter volumes by the number of male andfemale building occupants and sum thesevolumes to obtain the daily total potablewater use volume (see Equation 2).
4. Multiply total daily potable water vol-ume by the number of workdays in a typi-cal year to obtain the total annual potablewater volume use for the building. If rain-water harvest or graywater reuse strate-gies are employed in the building, sub-tract these annual volumes from the totalpotable water use (see Equation 3).
Repeat the above calculation methodol-ogy for the baseline case. Use EPAct fix-ture flow rates for the baseline case. Donot change the number of building occu-pants, the number of workdays or the fre-quency data. Do not include graywateror rainwater harvest volumes. Sampleflush and flow fixture flow rates are pro-vided in Table 2 and Table 3.
An example potable water use calculationis included for a two-story office build-ing with a capacity of 300 persons. Oc-cupant fixtures that use potable water in-clude water closets, urinals, lavatories,kitchen sinks and showers. Calculationsare based on a typical 8-hour workday and260 workdays per year.
It is assumed that building occupants are50% male and 50% female. Male occu-pants are assumed to use water closets once
Equation 1:
Equation 3:
Equation 2:
]flushor[minUse
]gal[VolumeWater]flushesors[minDurationUses]gal[
WaterPotableUse
××=
]gal[SewageFemale
GenerationFemale
Occupants]gal[
SewageMaleGeneration
MaleOccupants
]gal[PotableDailyVolumeWater
×+×=
]gal[GraywaterAnnual
HarvestRainwaterorYear
WorkdaysOccupants
day
gal
DayOccupant
UseWater]gal[
PotableTotalUseWater
−××
⋅
=
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Table 4: Design Case
Daily Uses
Flowrate Duration OccupantsWater
Use
[GPF] [flush] [gal]
0 0.8 1 150 0
3 0.8 1 150 360
1 0.0 1 150 0
0 0.0 1 150 0
2 0.0 1 150 0
0 0.0 1 150 0
Daily Uses
Flowrate Duration OccupantsWater
Use
[GPM] [sec] [gal]
3 2.5 12 300 450
1 2.5 12 300 150
0.1 2.5 300 300 375
Total Daily Volume [gal] 1,335
Annual Work Days 260
Annual Volume [gal] 347,100
(36,000)
TOTAL ANNUAL VOLUME [gal] 311,100
Waterless Urinal (Male)
Conventional Lavatory
Ultra Low-Flow Water Closet (Male)
Ultra Low-Flow Water Closet (Female)
Composting Toilet (Male)
Composting Toilet (Female)
Waterless Urinal (Female)
Kitchen Sink
Shower
Flush Fixture
Flow Fixture
Graywater Reuse Volume [gal]
and urinals twice in a typical work day.
Female occupants are assumed to usewater closets three times. All occupantsin this example are assumed to use lava-tories for each restroom use for 15 sec-onds and kitchen sinks once for 15 sec-onds. An estimated 10% of the building
occupants use showering facilities on atypical day.
Water closets use graywater volumes cap-tured from showers, sinks and lavatoriesin the building. Waterless urinals are usedin male restrooms and these fixtures useno water. Showers, lavatories and kitchen
sinks are conventional fixtures and use 2.5GPM. Motion sensors and electroniccontrols are used on lavatories, sinks andwater closets. These devices are estimatedto reduce lavatory and sink use durationby 20% but do not reduce the flow ofwater closets. These fixtures’ durationdata have been correspondingly adjustedfrom 15 seconds to 12 seconds. All ofthe above data is specific to the designcase.
Table 4 provides a summary of the de-sign case. The calculations indicate an-nual potable water use of 311,100 gal-lons.
The baseline case is calculated in the samemanner as the design case except that ALLfixtures are assumed to be standard fix-tures that comply with the Energy PolicyAct of 1992. Also, automatic sensors arenot used on any fixtures and there is nograywater reuse. Usage rates, occupancyand annual workdays are identical for thebaseline and the designed building. Table5 provides a summary of the baseline case.The calculations estimate an annual po-
table water use of 620,100 gallons.
Comparison of the design case to thebaseline case indicates that a potable wa-ter savings of 309,000 gallons is realizedby using low-flow water closets, waterlessurinals, auto controls on lavatories andsinks, and graywater reuse. This equatesto a savings of 50% over the baseline case.
Other building equipment that uses po-table water can also be considered forwater efficiency. For instance, water-effi-cient cooling towers can be specified in-stead of conventional cooling towers. Firesuppression systems and irrigation systemsare not applicable to this credit. Build-ing equipment should be included in thedesign case calculations as well as in thebaseline calculations.
When reusing graywater volumes fromthe building, it is necessary to model thesystem on an annual basis to determinegraywater volumes generated, storage ca-pacity of the system and any necessarytreatment processes before reusing thewater volumes. Graywater volumes may
Table 5: Baseline Case
Daily Uses
Flowrate DurationAuto
ControlsOccupants
Water Use
[GPF] [flush] N/A [gal]
1 1.6 1 150 240
3 1.6 1 150 720
2 1.0 1 150 300
0 1.0 1 150 0
Daily Uses
Flowrate DurationAuto
ControlsOccupants
Water Use
[GPM] [second] N/A [gal]
3 2.5 15 300 563
1 2.5 15 300 188
0.1 2.5 300 300 375
Total Daily Volume [gal] 2,385
Annual Work Days 260
TOTAL ANNUAL VOLUME [gal] 620,100
Shower
Conventional Water Closet (Male)
Conventional Water Closet (Female)
Conventional Urinal (Male)
Conventional Urinal (Female)
Flush Fixture
Flow Fixture
Conventional Lavatory
Kitchen Sink
U.S. Green Building Council
106
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Rainwater Volume [gal] = collection area [SF] x collection efficiency [%] x average rainfall [in] x 0.6233 gal/in
Equation 4:
or may not be consistently availablethroughout the year because these vol-umes are dependent on building occupantactivities.
For instance, in a typical office building,graywater volumes will change slightlydue to vacation schedules and holidaysbut should be relatively consistent overthe year. In contrast, graywater volumesin a school building will substantially de-crease in summer months due to theschool calendar, and, therefore, graywatervolumes may not be available for non-potable applications.
If the project uses rainwater volume fornon-potable uses, it is necessary to calcu-late water savings over a time period ofone year. Rain harvest volume dependson the amount of precipitation that theproject site experiences and the rainwatercollection surface’s area and efficiency. SeeEquation 4 and consult a rainwater har-vesting guide for more detailed instruc-tion. Rainfall data is available from thelocal weather service (see the Resourcessection). Rainwater volume depends onvariations in precipitation, and, thus, it isnecessary to model the reuse strategy onan annual basis. A model of rainwatercapture based on daily or monthly pre-cipitation and occupant demand is help-ful to determine the rainwater volumescaptured and storage tank size. Subtractannual rainwater use as budgeted for flushand flow fixtures in the design case calcu-lations.
Resources
Web Sites
American Rainwater Catchment Sys-tems Association
www.arcsa-usa.org
Includes a compilation of publications,such as the Texas Guide to Rainwater Har-vesting.
An Environmental Building News articleon commercial composting toilets.
National Climatic Data Center
www.ncdc .noaa .gov /oa /c l imate /stateclimatologists.html
Useful for researching local climate data,such as rainfall data for rainwater harvest-ing calculations. Includes links to stateclimate offices.
Terry Love’s Consumer Toilet Reports
www.terrylove.com/crtoilet.htm
This Web site offers a plumber’s perspec-tive on many of the major toilets used incommercial and residential applications.
Water Efficiency Article
home.earthlink.net/~wliebold
An opinion survey addressing variousbrands of water-efficient toilets andshowerheads.
WaterWiser: The Water EfficiencyClearinghouse
www.waterwiser.org, (800) 926-7337
The American Water Works Association’sclearinghouse includes articles, referencematerials and papers on all forms of wa-ter efficiency.
Print Media
Water, Sanitary and Waste Services forBuildings, Fourth Edition, by A. Wiseand J. Swaffield, Longman Scientific &Technical, 1995.
LEED-NC Version 2.1 Reference Guide
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Case Study
King Street CenterSeattle, Washington
The King Street Center is an office building that houses severaldepartments of the King County government. To reduce po-table water use and harvest site resources, the building was de-signed to collect rainwater from 44,000 square feet of roof areaand store it in three 5,400-gallon tanks in the basement. Thewater is pumped from the tanks through a filtration system andinto a graywater piping system that services water closets on eachfloor of the eight-story building. Rainwater provides 1.4 milliongallons of graywater or about two-thirds of the total water closetdemand, the remainder of which is made up by potable watervolumes. As a result, stormwater volumes leaving the site arereduced by about two-thirds.
OwnerKing County
Courtesy of King County
Definitions
A Composting Toilet is a dry plumbingfixture that contains and treats humanwaste via microbiological processes.
Fixture Sensors are applied to lavatories,sinks, water closets and urinals to sensefixture use and automatically turn on andoff.
A Waterless Urinal is a dry plumbing fix-ture that uses advanced hydraulic designand a buoyant fluid instead of water tomaintain sanitary conditions.
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