leed ratings

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LEED-NC Version 2.2 Reference Guide

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Alternative TransportationParking Capacity

Credit 4.4

1 Point

IntentReduce pollution and land development impacts from single occupancy vehicle use.

Requirements

OPTION 1 NON-RESIDENTIAL

Size parking capacity to meet, but not exceed, minimum local zoning requirements,AND, provide preferred parking for carpools or vanpools for 5% of the total providedparking spaces.

OR

OPTION 2 NON-RESIDENTIAL

For projects that provide parking for less than 5% of FTE building occupants: Provide preferred parking for carpools or vanpools, marked as such, for 5% of total

provided parking spaces.

OR

OPTION 3 RESIDENTIAL

Size parking capacity to not exceed minimum local zoning requirements, AND,provide infrastructure and support programs to facilitate shared vehicle usage suchas carpool drop-off areas, designated parking for vanpools, or car-share services, rideboards, and shuttle services to mass transit.

OR

OPTION 4 ALL

Provide no new parking.

Preferred parking refers to the parking spots that are closest to the main entrance of theproject (exclusive of spaces designated for handicapped) or parking passes provided at adiscounted price.

Potential Technologies & Strategies

Minimize parking lot/garage size. Consider sharing parking facilities with adjacentbuildings. Consider alternatives that will limit the use of single occupancy vehicles.

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U.S. Green Building Council

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IDEASS WE MR EQ Summary of ReferencedStandard

There is no standard referenced for thiscredit.

Approach andImplementation

The intent of this credit is to limit availabil-ity of parking as a means of encouragingthe use of alternative forms of transporta-tion to and from the site. Select a projectsite that is easily accessible from residentialareas by bicycle or public transportation.Once the site is selected, determine theexpected number of cars likely to drive tothe site and compare this number to local

zoning requirements. If parking demandis expected to be less than that requiredby local codes, consider seeking a variancewith the appropriate authorities to provideless parking. However, any on-site parkingreductions should be carefully balancedwith community needs to avoid needlesslyburdening surrounding neighborhoodswith excessive street parking.

Where possible, develop transportationdemand management strategies in order

to reduce the number of parking spacesrequired to meet the needs of occupants.Transportation demand strategies mayinclude the publishing of an employeeroster with addresses to assist people infinding carpool partners, creating incentiveprograms for carpooling, providing a rideshare board, or setting parking fees at alevel sufficient to encourage carpooling.

Calculations

Option 1Non-Residential

Determine the minimum number ofparking spaces required by local zoning

Credit 4.4

requirements. Total the parking spacesprovided for the project (excluding servicelots) and verify that the project parkingdoes not exceed the minimum required.

Determine the number of spaces 5%

represents (rounding up to the next wholenumber) and designate the appropriatesquare foot area, closest to the building en-trance and excluding handicapped spaces,as reserved carpool/vanpool spaces.

Option 2Non-Residential

For projects that provide parking for lessthan 5% of FTE building occupants:

1. Identify the total number of full-timeand part-time building occupants.

2. Calculate the Full-Time Equivalent(FTE) building occupants based ona standard 8-hour occupancy period.An 8-hour occupant has an FTE valueof 1.0 while a part-time occupant hasa FTE value based on their hours perday divided by 8 (see Equation 1).Note that FTE calculations for theproject must be used consistently forall LEED-NC credits. In buildingswith multiple shifts, use only the high-est volume shift in the FTE calcula-

tion but consider shift overlap whendetermining peak building users.

3. Determine if the total number of pro-vided parking spaces is less than 5% ofFTE occupants.

4. Designate project parking (closest tothe building entrance and excludinghandicapped spaces) equivalent to 5%of the total provided project parkingas reserved carpool/vanpool spaces.

Option 3ResidentialNo calculations are needed for residentialprojects beyond what is needed to complywith local zoning requirements.

FTE Occupants = Occupant Hours

8

Equation 1

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IDEASS WE MR EQOption 4All

No calculations are required for thiscompliance path.

Exemplary Performance

Projects may be awarded one innovationpoint for Exemplary performance in al-ternative transportation, SS Credit 4, byinstituting a comprehensive transporta-tion management plan that demonstratesa quantifiable reduction in personal auto-mobile use through the implementationof multiple alternative options.

Submittal Documentation

This credit is submitted as part of theDesign Submittal.

The following project data and calcula-tion information is required to documentcredit compliance using the v2.2 Submit-tal Templates:

Provide the FTE occupancy for theproject.

Provide the total parking capacity ofthe site.

Confirm the appropriate project com-pliance path.

In addition, please provide the followingproject data and calculation informationbased on the appropriate compliancepath:

Option 1 Non-Residential

Provide the number of parking spacesrequired for the project per local codeor ordinance.

Provide the number of carpool/van-pool spaces that are on-site.

Option 2 Non-Residential

Provide the number of carpool/van-pool spaces that are on-site.

Option 3Residential

Provide a description of the infra-structure/programs that are in placeto support and promote ridesharing.

Option 4 All

There are no additional items requiredfor this compliance path.

AND (For Projects With Special Circum-stancesAny Compliance Path)

Provide an optional narrative to de-scribe any special circumstances ornon-standard compliance paths takenby the project.

Considerations

Environmental Issues

Reducing the use of private automobilessaves energy and avoids environmentalproblems associated with automobile use,such as vehicle emissions that contributeto smog and other air pollutants and theenvironmental impacts associated with oilextraction and petroleum refining. Theenvironmental benefits of carpooling aresignificant. For example, 100 people whocarpooled (2 people per car) 10 miles towork and 10 miles home instead of driv-ing separately would prevent emission of7.7 pounds of hydrocarbons, 55 poundsof carbon monoxide, 3.3 pounds of nitro-gen oxides, 990 pounds of carbon dioxideand 50 gallons of gasoline per day.

Parking facilities for automobiles also havenegative impacts on the environment,since asphalt surfaces increase stormwaterrunoff and contribute to urban heat islandeffects. By restricting the size of parking

lots and promoting carpooling, buildingscan reduce these effects while benefitingfrom reduced parking requirements andmore and healthier green space.

Economic Issues

Carpooling reduces the size of the park-ing areas needed to support building oc-

Credit 4.4

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66

IDEASS WE MR EQ cupants, allowing the building to acceptmore occupants without enlarging theparking area. It helps reduce the cost ofland added for parking as well as infra-structure needed to support vehicles. Re-duction in parking areas can decrease the

amount of impervious surfaces on a site.This may result in reduced stormwatercharges, as some local utilities charge forstormwater based on impervious surfacearea. Also, many municipalities and stategovernments offer tax incentives for car-pooling programs, since fewer cars on theroad reduces pollution, traffic congestionand wear and tear to roadways.

Resources

Please see the USGBC website atwww.usgbc.org/resources for more specificresources on materials sources and othertechnical information.

Websites

Advanced Transportation TechnologyInstitute

www.atti-info.org

(423) 622-3884

A nonprofit organization that advancesclean transportation technologies throughresearch, education and technology trans-fer in order to promote a healthy environ-ment and energy independence.

Definitions

ACarpool is an arrangement in whichtwo or more people share a vehicle fortransportation.

Preferred Parkingrefers to the parkingspots that are closest to the main entranceof the project, exclusive of spaces des-ignated for handicapped, or to parkingpasses provided at a discounted price.

Credit 4.4

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Stormwater DesignQuantity Control

Credit 6.1

1 Point

IntentLimit disruption of natural hydrology by reducing impervious cover, increasing on-siteinfiltration, and managing stormwater runoff.

Requirements

OPTION 1 EXISTING IMPERVIOUSNESS IS LESS THAN OR EQUAL TO50%

Implement a stormwater management plan that prevents the post-development peakdischarge rate and quantity from exceeding the pre-development peak discharge rateand quantity for the one- and two-year, 24-hour design storms.

OR

Implement a stormwater management plan that protects receiving stream channels fromexcessive erosion by implementing a stream channel protection strategy and quantitycontrol strategies.

OR

OPTION 2 EXISTING IMPERVIOUSNESS IS GREATER THAN 50%

Implement a stormwater management plan that results in a 25% decrease in the volumeof stormwater runoff from the two-year, 24-hour design storm.


Design the project site to maintain natural stormwater flows by promoting infiltration.

Specify vegetated roofs, pervious paving, and other measures to minimize impervioussurfaces. Reuse stormwater volumes generated for non-potable uses such as landscapeirrigation, toilet and urinal flushing and custodial uses.

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Credit 6.1

Summary of ReferencedStandard



The approach to this credit may varysignificantly depending on the conditionof the project site at the beginning of theproject. If the project is being constructedon a largely undeveloped site, the goal isto preserve stormwater flows and designthe project to respond to the natural soilconditions, habitat, and rainfall charac-teristics. If the project is a redevelopment

of a previously developed site, the goal istypically to improve stormwater manage-ment in a way that restores the naturalfunctions of the site to the maximumextent practicable.

The approach to this credit also varies dra-matically between different regions andclimate zones. The strategies employedin an urban environment where water isdischarged to concrete channels and thenthe ocean are different from the strategies

employed at an inland site that dischargesto a small stream and lake system.

The most effective method to minimizestormwater runoff volume is to reduce theamount of impervious area. By reducingimpervious area, stormwater infrastruc-ture can be minimized or deleted from theproject. Strategies to minimize or mitigateimpervious surfaces may include:

Smaller building footprint

Pervious paving materials

Stormwater harvesting for reuse inirrigation and/or buildings

Green roofs

Bioswales/vegetated filter strips

Retention ponds

Clustering development to reducepaved surfaces (roads, sidewalks, etc.)

Guidelines for Capturing andReusing Stormwater Runoff

Stormwater captured (or harvested) incisterns, rain barrels, or other devices, isa primary source of water in many parts

of the world. Stormwater should not beused for potable needs if there are sourcesavailable that pose less risk to publichealth. However, harvested stormwatermay be used to reduce potable water needsfor uses such as landscape irrigation, firesuppression, toilet and urinal flushing,and custodial uses.

Storage and reuse techniques range fromsmall-scale systems (e.g., rain barrels) tounderground cisterns that may hold largevolumes of water. Whether large or small,

stormwater harvesting system designsshould consider the following:

1. Water need for the intended usehowwill the harvested water be used andwhen will it be needed? For example,if the water is used to irrigate land-scaping for four summer months, theamount of water needed and the howoften the storage unit will refill mustbe considered. Usage requirements andthe expected volume and frequency of

rainfall must be determined.

2. Drawdownstorage system designmust provide for the use or release ofwater between storm events for the de-sign storage volume to be available.

3. Drainage Areathe size and nature(e.g., percent imperviousness) of thearea draining to the storage systemdetermines how much runoff will beavailable for harvesting.

4. Conveyance Systemreused storm-water and graywater systems mustnot be connected to other domesticor commercial potable water systems.Pipes and storage units should beclearly marked (e.g., Caution: Re-claimed Water, Do Not Drink).

5. Pretreatmentscreens or filters maybe used to remove debris and sedi-

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IDEASS WE MR EQment from runoff and to minimizepollutants.

6. Pressurizationuses for harvestedrainwater may require pressurization.For example, most irrigation systems

require a water pressure of at least 15psi to function properly. Stored waterhas a pressure of 0.43 psi per foot ofwater elevation, and the water pres-sure at the bottom of a ten-foot vaultwould be 4.3 psi (10 ft. x 0.43 psi).Pressurization (e.g., a pump, pressuretank and filter) costs more and createsa more useable system.

The amount of runoff reduced by astormwater harvesting system may beconsidered equal to its storage volume.

However, volume calculations must alsoconsider how often the system is emptiedand the interval between storm events.

Example:

Rainwater will be harvested from a 10,000sq.ft. roof (100% imperviousness). Thesystem will be designed to capture therunoff from 90% of the average annualrainfall (1 inch of rainfall for humid wa-tersheds). The volume of the proposedstorage system is the amount of runoffcaptured (Vr), which is calculated belowin Equation 1:

Other design considerations tank mustbe emptied before subsequent stormevents. Use a tank that is 10 ft x 10 ft x8 ft deep Total storage volume (V

s) =

800 cu.ft. Using a design storm intervalof three days (72 hours), the drawdown

rate (Qr) is calculated below in Equa-

tion 2:

In this example, the captured rain must bedrained within 3 days or at a minimumrate of 1.4 gpm for the tank to be emptied

for the next storm.Different municipalities, state and lo-cal governments have various designrequirements for capturing and reuse ofstormwater runoff. These requirementsrange from where stormwater may becaptured and used to length of timestormwater can be held in a cistern, tothe type of water treatment required be-fore reuse. Designers should check withthe governing administrative authorityto determine parameters which will af-

fect collection, use, and distribution ofcaptured stormwater.

Calculations

There are two compliance paths for thiscreditone for largely undeveloped sitesand one for largely developed sites.

Option 1Existing ImperviousnessIs Less Than Or Equal To 50%(Largely Undeveloped Sites)

Option 1-a: Discharge Rate andQuantity

Determine the pre-development dischargerate and quantity for the project. Thesevalues are typically calculated by the civilengineer using the surface characteristicsof the site and data on storm event fre-quency, intensity and duration. Calculate

Credit 6.1

Where, Rv

= 0.05 + (0.009) (I) = 0.05 + (0.009) (100) = 0.95R

v= Volumetric Runoff Coefficient

I = Percent Imperviousness

Equation Source: 2000 Maryland Stormwater Design Manual, Vol. I & II (MDE, 2000)

Vr =(P)(R

v)(A)

=(1)(0.95)(10,000 SF)

= 791.67 CF (5,922 gal)12 12

Equation 2

Qr= 800c.f.

259,200 sec= 0.003 cfs or 1.37 gpm

Equation 1

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IDEASS WE MR EQ rate and quantity for the one-year andtwo-year, 24-hour design storms.

Determine the post-development dis-charge rate and quantity for the projectconsistent with the pre-development

calculations. The post-development rateAND quantity must be equal to or lessthan the pre-development values to earnthis credit.

Option 1-b: Stream ChannelProtection

Describe the project site conditions, themeasures taken, and controls imple-mented as part of the project scope thatprevent excessive stream velocities and theassociated erosion. Include in the descrip-

tion numerical values for pre-develop-ment and post-development conditionsto demonstrate that the rate and quantityof stormwater runoff in the post-develop-ment condition are below critical valuesfor the relevant receiving waterways.

Option 2Existing ImperviousnessIs Greater Than 50% (LargelyDeveloped Sites)

Determine the pre-development dischargerate and quantity for the project. Thesevalues are typically calculated by the civilengineer using the surface characteristicsof the site and data on storm event fre-quency, intensity, and duration. Calculaterate and quantity for the one-year andtwo-year, 24-hour design storms.

Determine the post-development dis-charge rate and quantity for the projectconsistent with the pre-developmentcalculations. The post-development rateAND quantity must be at least 25% less

than the pre-development values to earnthis credit.


There is no exemplary performance pointavailable for this credit.



The following project data and calcula-tion information is required to document

credit compliance using the v2.2 Submit-tal Templates:

Option 1

Provide the pre-development site run-off rate (cfs).

Provide the pre-development site run-off quantity (cf).

Provide the post-development siterunoff rate (cfs).

Provide the post-development siterunoff quantity (cf).

OR

Provide a narrative describing the proj-ect site conditions, measures taken,and controls implemented to preventexcessive stream velocities and associ-ated erosion.

Figure 1 (Source Figure 1.4), excerptedfrom the Maryland Stormwater DesignManual, diagrams the potential increases

in critical discharge rate from develop-ment.

Option 2

Provide the pre-development site run-off rate (cfs).

Provide the pre-development site run-off quantity (cf).

Provide the post-development siterunoff rate (cfs).

Provide the post-development site

runoff quantity (cf).

Considerations


The intent of this credit is to limit thedisruption of the natural stormwater flowsthat results from development. Undevel-

Credit 6.1

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oped land has a certain capacity to absorbrainfall in the soils, vegetation and trees.Clearing of vegetation and/or constructionof impervious surfaces (i.e., roads, parkinglots and buildings) reduce the capacity ofthe land to absorb rainfall and increase theamount of stormwater runoff.

As areas are constructed and urban-ized, surface permeability is reduced,resulting in increased stormwater runoffvolumes that are transported via urbaninfrastructure (e.g., gutters, pipes andsewers) to receiving waters. These storm-water volumes contain sediment andother contaminants that have a negativeimpact on water quality, navigation andrecreation. Furthermore, conveyance andtreatment of stormwater volumes requiressignificant municipal infrastructure andmaintenance. Reducing the generation ofstormwater volumes helps maintain the

natural aquifer recharge cycle and assistin restoring depleted stream base flows.In addition, stormwater volumes do nothave to be conveyed to receiving watersby the municipality, and receiving watersare not impacted.

The geometry and health of streamsis closely linked to stormwater runoffvelocities and volumes. Increases in the

frequency and magnitude of stormwaterrunoff due to development can causeincreased bankfull events. As a result,the stream bed and banks are exposed tohighly erosive flows more frequently andfor longer periods. The resultant impactsmay include channel-widening or down-cutting or both.

Figures 2 and 3 (Source Figures 1.1and 1.2), excerpted from the MarylandStormwater Design Manual show theimpact of development of stormwaterflows and the increase in the volumetricrunoff coefficient as a function of siteimperviousness.

Economic Issues

If natural drainage systems are designedand implemented at the beginning ofsite planning, they can be integrated eco-nomically into the overall development.

Water detention and retention featuresrequire cost for design, installation andmaintenance. However, these features canalso add significant value as site amenitiesif planned early in the design. Smallerstormwater collection and treatment sys-tems lessen the burden on municipalitiesfor maintenance and repair, resulting in amore affordable and stable tax base.

Credit 6.1

Figure 1: Increased Frequency of Flows Greater than the Critical Discharge Rate in a Stream Channel

after Development

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Synergies and Trade-Offs

Stormwater runoff is affected significantlyby site topography, site design, and espe-cially quantity of impervious surface areato support transportation amenity design.It may be possible to reuse stormwaterfor non-potable water purposes such asflushing urinals and toilets, custodial ap-plications, and building equipment uses.

It is helpful to perform a water balance todetermine the estimated volumes of wateravailable for reuse. Stormwater runoffvolumes can also be reduced by designingthe building with underground parking,a strategy that also reduces heat islandeffects. Pervious paving systems usuallyhave a limit on transportation loads and

may pose problems for wheelchair acces-sibility and stroller mobility. If stormwatervolumes are treated on site, additional sitearea may need to be disturbed to constructtreatment ponds or underground facili-ties. Application of green roofs reducesstormwater volumes that may be intendedfor collection and reuse for non-potableapplications.

Resources

Websites

Please see the USGBC website at www.usgbc.org/resources for more specificresources on materials sources and othertechnical information.

Credit 6.1

Figure 2: Water Balance at a Developed and Undeveloped Site (Source: Schueler, 1987)

Figure 3: Relationship Between Impervious Cover and the Volumetric Runoff Coefficient (Source:

Schueler, 1987)

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81

IDEASS WE MR EQStormwater Best Management PracticeDesign Guide, EPA/600/R-04/121A,September 2004.

www.epa .gov/ORD/NRMRL/pu bs/600r04121/600r04121a.pdf

Maryland Stormwater Design Manualwww.mde.state.md.us/Programs/Wa-terPrograms/SedimentandStormwater/stormwater_design/index.asp

Definitions

Impervious Surfaces promote runoff ofprecipitation volumes instead of infiltra-tion into the subsurface. The impervious-ness or degree of runoff potential can beestimated for different surface materials.

Stormwater Runoff consists of watervolumes that are created during precipi-tation events and flow over surfaces intosewer systems or receiving waters. Allprecipitation waters that leave project siteboundaries on the surface are consideredto be stormwater runoff volumes.

Credit 6.1

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Credit 6.1

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Heat Island EffectNon-Roof

Credit 7.1

1 Point

IntentReduce heat islands (thermal gradient differences between developed and undevelopedareas) to minimize impact on microclimate and human and wildlife habitat.

Requirements

OPTION 1

Provide any combination of the following strategies for 50% of the site hardscape(including roads, sidewalks, courtyards and parking lots):

Shade (within 5 years of occupancy)

Paving materials with a Solar Reflectance Index (SRI)2 of at least 29

Open grid pavement system

OR

OPTION 2

Place a minimum of 50% of parking spaces under cover (defined as underground,under deck, under roof, or under a building). Any roof used to shade or cover parkingmust have an SRI of at least 29.


Shade constructed surfaces on the site with landscape features and utilize high-reflec-tance materials for hardscape. Consider replacing constructed surfaces (i.e., roof, roads,sidewalks, etc.) with vegetated surfaces such as vegetated roofs and open grid paving

or specify high-albedo materials to reduce the heat absorption.

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Credit 7.1

Summary of ReferencedStandard



Limit the amount of impervious hard-scape areas on the site in order to limitheat island effect. For features such asparking lots, roads and walkways, useopen grid pavement systems that are atleast 50% pervious, which remain coolerdue to reduction of impervious surfacearea and increased evaporation from theopen cell vegetation. Use light colored

paving surfaces, and shade paved areaswith landscaping. Utilize a parking deckto reduce parking footprint by 50%.

Darker paving materials, such as asphalt,generally exhibit low reflectance and con-sequently low SRI values. Grey or whiteconcrete has a higher reflectance and ahigher SRI. Concrete made with white ce-ment may cost up to twice as much as thatmade with gray cement. Some blendedcements (e.g., slag cements) are very light

in color and cost the same or slightly lessthan portland-only based gray cement(Source: Albedo: A Measure of Pave-ment Surface Reflectance, R&T Update#3.05, June 2002, American ConcretePavement Association, www.pavement.com/techserv/RT3.05.pdf ). Micro sur-faces and coatings over asphalt pavementcan be used to attain the required SRIvalue for this credit. Coatings and integralcolorants can be used in cementitiouspavers or cast-in-place parking surfacesto improve solar reflectance.

Vegetation can shade buildings and pave-ments from solar radiation and cool theair through evapotranspiration. Provideshade using native or adaptive trees, largeshrubs and non-invasive vines. Trellisesand other exterior structures can supportvegetation to shade parking lots, walk-

ways and plazas. Deciduous trees allowbuildings to benefit from solar heat gainduring the winter months. On-site loca-tions where tree planting is not possible,use architectural shading devices to blockdirect sunlight radiance.

Alternatively, place parking under cover.This can include using multi-story orsubterranean parking structures, or plac-ing parking under a shade structure.Parking cover must also meet the sameSRI requirements as non-roof impervi-ous surfaces.

Calculations

Option 1

1. Identify all non-roof hardscape sur-faces on the project site and sum thetotal area (T).

2. Identify all of the hardscape surfacesthat have an open grid paving systemthat are at least 50% pervious and sumthe total area (O).

3. Identify all of the hardscape featuresthat have an SRI of at least 29 and sumthe total area (R).

SRI is calculated using the LEEDSubmittal Template by inserting bothemissivity and reflectance values intothe worksheet and pressing Click toCalculate SRI. Emittance is calcu-lated according to ASTM E 408 orASTM C 1371 and Reflectance iscalculated according to ASTM E 903,ASTM E 1918, or ASTM C 1549.Alternatively, Table 1 provides a list ofSRI values for typical paving materials;where these materials are used, the SRI

values from this table may be used inlieu of obtaining specific Emissivityand Reflectance measurements.

4. Identify all of the hardscape featuresthat will be shaded by trees or otherlandscape features. Shade coverageshall be calculated at 10am, noon, and3pm. The arithmetic mean of these

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Credit 7.1

three values will be used as the effec-tive shaded area. Calculate the effectiveshaded area (S).

5. Sum the open space paving, highreflectance paving and shaded areasto get the qualifying area (Q) (See

Equation 1.)(Note that each surface should becounted only once. For example, a 10square foot area that is 55% pervious,has an SRI of 30 and is shaded by atree contributes only 10 square feet tothe total.)

6. The total qualifying area must begreater than or equal to 50% of the totalhardscape area (T), as in Equation 2.

Option 21. Calculate the total number of parking

spaces for the project.

2. Calculate the number of parkingspaces that are under cover (includingunderground, under the building, andunder shade structures. This numbermust equal at least 50% of the totalnumber of parking spaces.


Projects may be awarded an innovationpoint for exemplary performance by

demonstrating that either, 1) a minimumof 100% of non-roof impervious surfaceshave been constructed with high-albedomaterials and/or open grid paving and/orwill be shaded within five years; OR 2)100% of the on-site parking spaces have

been located under cover.


This credit is submitted as part of theConstruction Submittal.


Provide project site drawings, high-lighting the location of specific pavingmaterials, landscape shading, and/orunderground or covered parking.

AND

Option 1

Provide the following data in the submit-tal template:

The measured reflectance and emit-tance of each paving material installedon-site (to calculate the SRIORthe actual SRI for each paving materialinstalled on-siteORthe defaultSRI value for typical materials fromTable 1.

Material Emissivity Reflectance SRI

Typical New Gray Concrete 0.9 0.35 35

Typical Weathered* Gray Concrete 0.9 0.20 19

Typical New White Concrete 0.9 0.7 86

Typical Weathered* White Concrete 0.9 0.4 45

New Asphalt 0.9 .05 0

Weathered Asphalt 0.9 .10 6* Reflectance of surfaces can be maintained with cleaning. Typical pressure washing of cementious materials canrestore reflectance close to original value. Weathered values are based on no cleaning.

Table 1: Solar Reflectance Index (SRI) for Standard Paving Materials

Q = (O + R + S)

Q > T/2

Equation 2

Equation 1

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IDEASS WE MR EQ Total area of site hardscape

Total area of hardscape to be shadedwithin 5 years

Total area of installed SRI complianthardscape materials

Total area of open grid pavement

OR

Option 2

Total number of parking spaces pro-vided on-site

Total number of covered parkingspaces on-site

AND (For Either Compliance Option)

Provide an optional narrative to de-

scribe any special circumstances ornon-standard compliance paths takenby the project.

Considerations


As the built environment grows and re-places natural settings, it also relinquishesassociated ecological services. Vegetationcools the area surrounding it via shade and

evapotranspiration. The use of dark, non-reflective surfaces for parking, roofs, walk-ways and other surfaces contributes toheat island effects created when radiationfrom the sun is absorbed and transferredthrough convection and conduction backto surrounding areas. As a result of heatisland effects, ambient temperatures inurban areas can be artificially elevatedby more than 10F when compared withsurrounding suburban and undevelopedareas. This results in increased cooling

loads in the summer, requiring largerHVAC equipment and electrical de-mand resulting in more greenhouse gasand pollution generation, and increasedenergy consumption for building opera-tions. Heat island effects can be mitigatedthrough the application of shading andthe use of materials that reflect the sunsheat instead of absorbing it.

Heat island effects are detrimental to sitehabitat, wildlife and migration corridors.Plants and animals are sensitive to highertemperatures and may not thrive in areasthat are increasingly hot. Reduction of heatisland effect minimizes disturbance of local

microclimates. This can reduce summercooling loads that in turn reduce energyuse, greenhouse gas and pollution genera-tion, and infrastructure requirements.

Higher reflectance pavements do increaseoverall light levels and may allow thedesigner to use fewer fixtures. Designersshould weigh the benefits of using highlyreflective pavements to reduce heat islandeffect against possible energy savings fromreduced site lighting requirements. Light-

ing evaluations should include the evalu-ation of the inter-reflected component,and reflections off of high reflectancematerials, such as white concrete, whichcan result in glare and cause disabled vi-sion and increased light pollution. Stepsshould be taken to minimize the amountof light that is directed from site lightingfixtures directly down onto reflective pav-ing surfaces.

Economic Issues

According to the EPA, about $40 billionis spent annually in the United States toair-condition buildingsone-sixth of allelectricity generated in a year. Reductionin heat islands lowers the cost of coolingand HVAC equipment needs. Energy tocool buildings is a substantial cost over abuildings lifetime. Higher initial costs mayresult from installation of additional treesand architectural shading devices. However,these items have an acceptable payback

when integrated into a whole systems ap-proach that maximizes energy savings.

Resources

Please see the USGBC website atwww.usgbc.org/resources for more specificresources on materials sources and othertechnical information.

Credit 7.1

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IDEASS WE MR EQWebsites

Amer i can Concret e PavementAssociation

www.pavement.com

(847) 966-2272

National association representing concretepavement contractors, cement companies,equipment and material manufactur-ers, and suppliers. See the R&T Update#3.05, June 2002, Albedo: A measureof Pavement Surface Reflectance (www.pavement.com/techserv/RT3.05.pdf).

Heat Island Group

Lawrence Berkeley National Laboratory

http://eetd.lbl.gov/HeatIsland/

LBL conducts heat island research tofind, analyze, and implement solutionsto minimizing heat island effect, withcurrent research efforts focusing on thestudy and development of more reflectivesurfaces for roadways and buildings.

Heat Island Effect

U.S. Environmental Protection Agency

www.epa.gov/heatisland

(202) 343-9343

Basic information about heat island effect,its social and environmental costs, andstrategies to minimize its prevalence.

Definitions

Albedo is synonymous with solar reflec-tance (see below).

Emissivity is the ratio of the radiationemitted by a surface to the radiationemitted by a black body at the same

temperature.Heat Island Effects occur when warmertemperatures are experienced in urbanlandscapes compared to adjacent ruralareas as a result of solar energy retentionon constructed surfaces. Principal surfacesthat contribute to the heat island effectinclude streets, sidewalks, parking lotsand buildings.

Infrared Emittance is a parameter be-tween 0 and 1 that indicates the abilityof a material to shed infrared radiation.The wavelength of this radiant energy isroughly 5 to 40 micrometers. Most build-ing materials (including glass) are opaque

in this part of the spectrum, and have anemittance of roughly 0.9. Materials suchas clean, bare metals are the most im-portant exceptions to the 0.9 rule. Thusclean, untarnished galvanized steel haslow emittance, and aluminum roof coat-ings have intermediate emittance levels.

Non-Roof Impervious Surfaces includeall surfaces on the site with a perviousnessof less than 50%, not including the roofof the building. Examples of typically

impervious surfaces include parking lots,roads, sidewalks and plazas.

Open-Grid Pavement is defined forLEED purposes as pavement that is lessthan 50% impervious and contains veg-etation in the open cells.

Perviousness is the percent of the surfacearea of a paving material that is open andallows moisture to pass through the ma-terial and soak into the earth below thepaving system.

Solar Reflectance Index (SRI) is a mea-sure of a materials ability to reject solarheat, as shown by a small temperaturerise. It is defined so that a standard black(reflectance 0.05, emittance 0.90) is 0and a standard white (reflectance 0.80,emittance 0.90) is 100. For example, astandard black surface has a temperaturerise of 90F (50 C) in full sun, and a stan-dard white surface has a temperature riseof 14.6F (8.1C). Once the maximum

temperature rise of a given material hasbeen computed, the SRI can be computedby interpolating between the values forwhite and black.

Materials with the highest SRI values arethe coolest choices for paving. Due tothe way SRI is defined, particularly hotmaterials can even take slightly negative

Credit 7.1

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IDEASS WE MR EQ values, and particularly cool materials caneven exceed 100. (Lawrence Berkeley Na-tional Laboratory Cool Roofing MaterialsDatabase)

Underground Parkingis a tuck-under

or stacked parking structure that reducesthe exposed parking surface area.

Credit 7.1

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Heat Island EffectRoof

Credit 7.2

1 Point

IntentReduce heat islands (thermal gradient differences between developed and undevelopedareas) to minimize impact on microclimate and human and wildlife habitat.

Requirements

OPTION 1

Use roofingmaterials having a Solar Reflectance Index (SRI)3 equal to or greater thanthe values in the table below for a minimum of 75% of the roof surface.

OR

OPTION 2

Install a vegetated roof for at least 50% of the roof area.OR

OPTION 3

Install high albedo and vegetated roof surfaces that, in combination, meet the follow-ing criteria:

(Area of SRI Roof / 0.75) + (Area of Vegetated Roof / 0.5) >= Total Roof Area

Potential Technologies & StrategiesConsider installing high-albedo and vegetated roofs to reduce heat absorption. SRI iscalculated according to ASTM E 1980. Reflectance is measured according to ASTME 903, ASTM E 1918, or ASTM C 1549. Emittance is measured according to ASTME 408 or ASTM C 1371. Default values will be available in the LEED-NC v2.2 Ref-erence Guide. Product information is available from the Cool Roof Rating Councilwebsite, atwww.coolroofs.org.

Roof Type Slope SRI

Low-Sloped Roof 2:12 78

Steep-Sloped Roof 2:12 29

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IDEASS WE MR EQ Summary of ReferencedStandards

ASTM Standard E1980-01StandardPractice for Calculating Solar Reflec-tance Index of Horizontal and Low-

Sloped Opaque Surfaces.This standard describes how surface re-flectivity and emissivity are combined tocalculate a Solar Reflectance Index (SRI)for a roofing material or other surface.The standard also describes a laboratoryand field testing protocol that can be usedto determine SRI.

ASTM E408-71(1996)e1StandardTest Methods for Total Normal Emit-tance of Surfaces Using Inspection-

Meter Techniqueswww.astm.org

(610) 832-9585

This standard describes how to measuretotal normal emittance of surfaces usinga portable inspection-meter instrument.The test methods are intended for largesurfaces where non-destructive testingis required. See the standard for testingsteps and a discussion of thermal emit-tance theory.

ASTM E903-96Standard Test Meth-od for Solar Absorptance, Reflectance,and Transmittance of Materials UsingIntegrating Spheres

www.astm.org

(610) 832-9585

Referenced in the ENERGY STARroofing standard, this test method usesspectrophotometers and need only be ap-plied for initial reflectance measurement.

Methods of computing solar-weightedproperties from the measured spectralvalues are specified. This test methodis applicable to materials having bothspecular and diffuse optical properties.Except for transmitting sheet materialsthat are inhomogeneous, patterned, orcorrugated, this test method is preferred

over Test Method E1084. The ENERGYSTAR roofing standard also allows theuse of reflectometers to measure solarreflectance of roofing materials. See theroofing standard for more details.

ASTM E1 918 -9 7Sta ndard TestMethod for Measuring Solar Reflec-tance of Horizontal And Low-SlopedSurfaces in the Field

www.astm.org

(610) 832-9585

This test method covers the measurementsof solar reflectance of various horizontaland low-sloped surfaces and materials inthe field, using a pyranometer. The testmethod is intended for use when the sun

angle to the normal from a surface is lessthan 45 degrees.

ASTM C1 37 1-04 Standard TestMethod for Determination of Emit-tance of Materials Near Room Temper-ature Using Portable Emissometers

www.astm.org

(610) 832-9585

This test method covers a technique fordetermination of the emittance of typi-

cal materials using a portable differentialthermopile emissometer. The purpose ofthe test method is to provide a compara-tive means of quantifying the emittanceof opaque, highly thermally conductivematerials near room temperature as aparameter in evaluating temperatures,heat flow, and derived thermal resistancesof materials.

ASTM C1 54 9-04 Standard TestMethod for Determination of SolarReflectance Near Ambient TemperatureUsing a Portable Solar Reflectometer

www.astm.org

(610) 832-9585

This test method covers a technique fordetermining the solar reflectance of flatopaque materials in a laboratory or in thefield using a commercial portable solar

Credit 7.2

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IDEASS WE MR EQreflectometer. The purpose of the testmethod is to provide solar reflectancedata required to evaluate temperatureand heat flows across surfaces exposed tosolar radiation.


To maximize energy savings and minimizeheat island effects, materials must exhibita high reflectivity and a high emissivityover the life of the product. Since mul-tiple testing methods are available formeasuring emissivity and reflectance,check manufacturer literature carefullyto ensure use of appropriate data. For

example, some manufacturers measurevisible reflectance, which differs from thesolar reflectance measurement referencedin this credit. Visible reflectance correlatesto solar reflectance but the two quantitiesare not equal because solar gain covers awider range of wavelengths than visiblelight. A material that exhibits a high vis-ible reflectance usually has a lower solarreflectance. Typically, white roof productsexhibit higher performance characteristicsthan non-white products. Performance

varies by roofing materials as well as brand.Check with roofing manufacturers and theLawrence Berkeley National LaboratorysCool Roofing Materials Database (http://eetd.lbl.gov/CoolRoofs) for specific infor-mation. Table 1 provides example SRI

values for typical roof surfaces.

Green roofs are vegetated surfaces thatreduce heat island effect by replacing heat-absorbing surfaces with plants, shrubsand small trees that cool the air throughevapotranspiration (or evaporation ofwater from leaves). Green roofs provideinsulating benefits, aesthetic appeal, andlower maintenance than standard roofs.Some green roofs require plant mainte-nance and are considered active gardens,

while other gardens have grasses andplants that require no maintenance orwatering. All types of green roofs requiresemiannual inspection but have longerlifetimes than conventional roofs.

Calculations

1. Calculate the total roof surface areaof the project. Deduct areas withequipment, solar energy panels, andappurtenances.

Credit 7.2

Example SRI Values for Solar Infrared Temperature SolarGeneric Roofing Materials Reflectance Emittance Rise Reflectance

Index (SRI)

Gray EPDM 0.23 0.87 68F 21

Gray Asphalt Shingle 0.22 0.91 67F 22

Unpainted Cement Tile 0.25 0.9 65F 25

White Granular Surface Bitumen 0.26 0.92 63F 28

Red Clay Tile 0.33 0.9 58F 36

Light Gravel on Built-Up Roof 0.34 0.9 57F 37

Aluminum 0.61 0.25 48F 56

White-Coated Gravel on Built-Up Roof 0.65 0.9 28F 79

White Coating on Metal Roof 0.67 0.85 28F 82

White EPDM 0.69 0.87 25F 84

White Cement Tile 0.73 0.9 21F 90

White Coating - 1 Coat, 8 mils 0.8 0.91 14F 100

PVC White 0.83 0.92 11F 104

White Coating - 2 Coats, 20 mils 0.85 0.91 9F 107

Source: LBNL Cool Roofing Materials Database. These values are for reference only and are notfor use as substitutes for actual manufacturer data.

Table 1: Solar Reflectance Index (SRI) for Typical Roofing Materials

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IDEASS WE MR EQ 2. Determine the roof surface area thatmeets the applicable SRI criteria and/or the area that is covered by greenroof.

3. Determine whether the areas of cool

roof and green roof meet the creditrequirement, usingEquation 1.

Note: a weighted average calculationmay be performed for buildings withmultiple roof surfaces to demonstratethat the total roof area has an averageSRI equal to or greater than a theoreti-cal roof with 75% at an SRI of 78 and25% at an SRI of 30.


This credit may be eligible for exemplaryperformance under the Innovation &Design section if 100% of the projectsroof area (excluding mechanical equip-ment, photovoltaic panels, and skylights)is comprised of a green roof system.




Provide copies of the projects roofdrawings to highlight the location ofspecific roof materials and/or greenroof systems.

AND

Option 1

Total area of installed SRI compliantroofing materials

Provide a listing of installed roofingmaterials and their SRI values

OR

Option 2

Total area of installed green roofsystems

OR

Option 3

Total area of installed green roof sys-tems

Total area of installed SRI compliantroofing materials

Provide a listing of installed roofingmaterials and their SRI values

AND

Provide an optional narrative to de-scribe any special circumstances or

non-standard compliance paths takenby the project.

Considerations


The heat island effect raises the localizedtemperature, impacting local microcli-mate. Plants and animals that are sensi-tive to large fluctuations in daytime andnighttime temperatures may not thrivein areas affected by heat islands. Heatislands also exacerbate air pollution fortwo reasons. First, smog is produced fasterat higher temperatures. Secondly, risingtemperatures lead to increased coolingrequirements, requiring energy and caus-ing associated emissions.

Garden roofs reduce stormwater vol-umes that may be collected and used fornonpotable purposes. Stormwater runoffvolumes from garden roofs depend onthe local climate, depth of soil, plant

types, and other variables. However, allgarden roofs decrease runoff volumessubstantially.

Credit 7.2

(Area of SRI Roof / 0.75) + (Area of vegetated roof / 0.5) >= Total Roof Area

Equation 1

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Credit 7.2

Economic Issues

Green roofs or roofs with high Solar Re-flectance Indexes reduce costs associatedwith cooling and HVAC equipment.Green roofs typically require an additional

up-front investment, while cool roofsmay or may not cost more than otherroofs. However, any up-front investmentis likely to result in energy cost savingsthroughout the lifecycle of the project. Inaddition, an increasing number of locali-ties are beginning to require the use ofcool roofs on new building projects.

Buildings in very cold climates may notexperience year-round energy benefitsfrom reflective roofing due to high emit-tance and low absorption, which may

increase heating costs. However, increasingthe reflectance of a roof reduces annualcooling energy use in almost all climates.

Resources

Websites

Cool Roof Rating Council

www.coolroofs.org

A nonprofit organization dedicated to

implementing and communicating fair,accurate, and credible radiative energyperformance rating systems for roof sur-faces, supporting research into energy-related radiative properties of roofingsurfaces, including durability of thoseproperties, and providing education andobjective support to parties interested inunderstanding and comparing variousroofing options.

EPA ENERGY STAR Roofing

Productswww.energystar.gov/index.cfm?c=roof_prods.pr_roof_products

This site provides solar reflectance levelsrequired to meet ENERGY STAR label-ing requirements.

Extensive Green Roofs

www.greenroofs.php

This Whole Building Design Guidearticle by Charlie Miller, PE details thefeatures and benefits of constructinggreen roofs.

Greenroofs.com

www.greenroofs.comThe green roof industry resource portaloffers basic information, product andservice directory, and research links.

Lawrence Berkeley National Labora-tory Heat Island GroupCool Roofs

h t tp : / / e e td . l b l . gov /Hea t I s l a n d/CoolRoofs/

This site offers a wealth of informationabout cool roof research and technology,

including links to the Cool Roofing Ma-terials Database.

Penn State Center for Green RoofResearch

http://hortweb.cas.psu.edu/research/greenroofcenter/

The Center has the mission of demon-strating and promoting green roof re-search, education and technology transferin the Northeastern United States.

Definitions

Albedo is synonymous with solar reflec-tance (see below).

Heat Island Effects occur when warmertemperatures are experienced in urbanlandscapes compared to adjacent ruralareas as a result of solar energy retentionon constructed surfaces. Principal surfacesthat contribute to the heat island effectinclude streets, sidewalks, parking lots

and buildings.Infrared or Thermal Emittance is aparameter between 0 and 1 (or 0% and100%) that indicates the ability of a mate-rial to shed infrared radiation (heat). Thewavelength range for this radiant energy isroughly 3 to 40 micrometers. Most build-ing materials (including glass) are opaquein this part of the spectrum, and have an

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IDEASS WE MR EQ emittance of roughly 0.9.Materials such asclean, bare metals are the most importantexceptions to the 0.9 rule. Thus clean,untarnished galvanized steel has low emit-tance, and aluminum roof coatings haveintermediate emittance levels.

Solar Reflectance (albedo) is the ratioof the reflected solar energy to the in-coming solar energy over wavelengths ofapproximately 0.3 to 2.5 micrometers.A reflectance of 100% means that all ofthe energy striking a reflecting surface isreflected back into the atmosphere andnone of the energy is absorbed by the sur-face. The best standard technique for itsdetermination uses spectro-photometricmeasurements with an integrating sphere

to determine the reflectance at each dif-ferent wavelength. An averaging processusing a standard solar spectrum thendetermines the average reflectance (seeASTM Standard E903).

Solar Reflectance Index (SRI) is a mea-sure of a materials ability to reject solarheat, as shown by a small temperaturerise. It is defined so that a standard black(reflectance 0.05, emittance 0.90) is 0and a standard white (reflectance 0.80,

emittance 0.90) is 100. For example, astandard black surface has a temperaturerise of 90F (50C) in full sun, and a stan-dard white surface has a temperature riseof 14.6F (8.1C). Once the maximumtemperature rise of a given material hasbeen computed, the SRI can be computedby interpolating between the values forwhite and black.

Materials with the highest SRI values arethe coolest choices for roofing. Due tothe way SRI is defined, particularly hotmaterials can even take slightly negativevalues, and particularly cool materials caneven exceed 100. (Lawrence Berkeley Na-tional Laboratory Cool Roofing MaterialsDatabase)

Credit 7.2

leed ratings

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