Summary and critique of "LEED" 2009 Green Building Design & Construction Reference Guide

Jonathan Ochshorn

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Following is my summary and critique of the Green Building Design & Construction Reference Guide, 2009 Edition. Commentary on the Reference Guide can be found in these red boxes, sometimes within each of the chapter links immediately above, but mostly in my summary and critique of the prior version: Version 2.2 NC.

2. Sustainable Sites (SS)

Overview

Site involves two things: selection and development.

Development issues include landscape, hardscape, and "exterior building issues."

Selection involves: avoiding greenfields, agricultural lands, wetlands, habitats for wildlife, or sites on water bodies. Conversely, the guidelines encourage the restoration of damaged sites or previously developed sites. Also encouraged are plans that integrate a project into an existing community, so that new infrastructure is not needed.

Reducing vehicular emissions is a concern accounted for in the SS credits. The justification includes both pollution reduction as well as storm water issues (less hardscape in the form of roads and roofs).

Less hardscape also helps reduce the heat island effect (which reduces the cooling loads on buildings).

Promote mass transit.

Use plantings that don't require irrigation or chemicals. Plantings help prevent erosion (better water quality, less flooding). Use native or adapted plants. Reduces maintenance costs.

Reduce light pollution.

The "site" is defined by limits of ownership (private property). Where multiple buildings are on a single site (campus plan), the building's "site" is defined (by the project team) for that single building and must be used consistently for all credits.

Overview of credits: 2 prerequisites and 10 credits.

SS Prerequisite 1 Construction activity pollution prevention

Intent: Reduce construction-related pollution related to disruption of soil.

Requirements: Make erosion and sedimentation control plan for the entire construction phase. Conform with EPA 2003 Construction General Permit or local standards (choose more stringent of the two). The 3 issues are: 1) erosion of soil (water or wind); protection of stockpiled topsoil; 2) sedimentation of storm sewers or streams; 3) dust in air. EPA guidelines can be found at: http://cfpub.epa.gov/npdes/stormwater/cgp.cfm

1. Benefits/issues. Preserving topsoil is important, both for the site and for water bodies downstream. The issues dealt with in this prerequisite are mostly mandated by local building codes in any case, and involve small additional expenses.

2. Related credits. Yes.

3. Referenced standards. See above (EPA site)

4. Implementation: place erosion and sedimentation plans into the contract drawings and specifications. Common strategies include temporary or permanent seeding, mulching (these for stabilization of the soil); or "structural controls" such as earth dikes, silt fences, sediment traps, or sediment basins.

5. Timeline and team.

6. Calculations: none

7. Documentation guidance.

8. Examples.

9. Exemplary performance: N/A

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: erosion; eutrophication (increase of chemical nutrients -- nitrogen, phosphorous -- in the ecosystem; can reduce oxygen in bodies of water by stimulating plant growth, algal blooms, or weeds; NPDES (National Pollutant Discharge Elimination System) is the EPA's permit system for regulating point-source water pollutants; sedimentation (adds soil particles to water bodies); stromwater pollution prevention plan; stormwater runoff is water (from rain, etc.) flowing over the surface of the ground across site boundaries.

SS Credit 1 Site selection (1 point)

Intent: Choose appropriate sites and locate buildings to reduce negative impacts.

Requirements: Do not put buildings, roads, hardscape on: prime farmland; undeveloped land in the flood plane (i.e., 5 ft. or lower than the 100-year flood elevation); land used as habitat for threatened or endangered species; land near wetlands (within 100 ft., or as defined by local ordinance); undeveloped land near lakes, seas, rivers, streams, etc. "that could support fish, recreation or industrial use" (within 50 ft., or as defined by local ordinance); parkland (except where a parkland trade is accepted).

[From Version 2.2 critique] This last point is a bit puzzling: LEED advises that buildings should not be sited near water bodies that might be used for industry instead. While this might be sensible from the standpoint of economic growth, it's not clear how it relates to the goal of sustainable development, as the unsustainable industrial use of water bodies is itself a major issue.

1. Benefits/issues. Limits environmental damage by finding sites that are already damaged (or already used for development); preserves habitat.

[From Version 2.2 critique] It is not clear why building in the flood plane, or near a water body, becomes desirable simply because the site has already been inappropriately developed. The same environmental hazards exist, whether such a site has or hasn't been previously developed.

2. Related credits. Yes.

3. Referenced standards. USDA definition of prime agricultural land. [note that such agricultural land is often itself associated with habitat destruction]; FEMA definition of flood elevations; US Fish and Wildlife Service and national Marine Fisheries Service lists of threatened and endangered species; US Code of Federal Regulations definition of wetlands.

4. Implementation. Build in consolidated areas within the larger site; identify and save natural features; design to prevent bird collisions (avoid glazing in some orientations and reflections of vegetation).

5. Timeline and team.

6. Calculations. None

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations. N/A

11. Operations/maintenance.

12. Resources.

13. Definitions: development footprint includes hardscape, roads, buildings; ecosystem; endangered species; previously developed sites (somehow altered by humans).

SS Credit 2 Development density and community connectivity (5 points)

Intent: Prioritize urban development (i.e., anti-sprawl) to protect greenfields and so on.

Requirements: Two options. Either (1) use previously developed site AND locate in community with density of 60,000 sq.ft. per acre (net, also check the project density by itself) -- this is equivalent to a 2-story downtown development; or (2) build on previously developed site within 1/2 mile of residential area (or neighborhood with 10 units/acre net) that is also within 1/2 mile of 10 "basic services" (e.g., bank, church, grocery, day care, cleaners, post office, museum, etc., 1 of which may be in the project itself, and 8 of which must be actually already there) and has some sort of pedestrian link to these services. The 1/2 mile is measured in a straight line from the main building entrance (i.e., draw a circle with 1/2 mile radius and count...).

1. Benefits/issues. Standard critique of sprawl. "...improve productivity of building occupants by reducing the time spent driving and finding parking space." Improve health by walking. Potential problems are lack of open space and daylighting, and various types of pollution.

[From Version 2.2 critique] The LEED commentary suggests that such development improves worker productivity and occupant health: productivity because workers spend less time driving (as if workers somehow automatically live near their places of employment simply because a workplace is located within 1/2 mile of some residential area; and as if workers with shorter commute times spend the "extra" minutes thereby obtained by arriving early at work and donating free labor to their employers); and health because of increased physical activity as people walk the 1/2 mile to the grocery store and carry back bread and pork chops to their homes (as if 1/2 mile walks seriously count as physical activity; and as if this small-town model of local grocery stores and daily walks to shop for fresh vegetables corresponds to actual life as we know it — this is clearly written by people who have never experienced the unrelenting exhaustion brought about by actually working, shopping, preparing meals, and raising families).

LEED introduces the concept of trade-offs here: the idea that there may be negative environmental consequences for following the advice leading to a particular credit. Specifically, the commentary notices that those who build in "dense" urban areas may encounter "limited open space and possible negative IAQ aspects such as contaminated soils, undesirable air quality or limited daylighting applications." But LEED has no mechanism for subtracting points corresponding to these, or other, potentially negative consequences of a particular development. Instead, each "credit" is considered independently, potentially leading to certification of a building that has numerous negative environmental features.

Note that maximizing urban development (high density) is rewarded here, while maximizing open space (low density) is rewarded elsewhere (see Credit 5 in this section). The implicit argument that greenfields, unlike urban areas, should remain as undeveloped as possible only makes "sense" in the context of a planet carved up into parcels of privately owned real estate, each developed according to the calculations of its owner. Such a situation precludes examining the logic of consolidating development, even in greenfields.

Finally, LEED defends urban development by criticizing "sprawl," using two familiar arguments: first, commuters spend more time commuting (in cars), and may require additional cars to support their suburban lifestyles; second, by developing projects in cities, cities are restored and invigorated, which creates "a more stable and interactive community." Unfortunately, this second argument lacks historical perspective. It is precisely the congestion of urban areas that leads to the development of interstate highways and the redefinition of growth centered on the nodes created at the intersections of such highways (see Joel Garreau's 1991 Edge City). The ideal of living 1/2 mile from both one's workplace as well as "basic services" abstracts from the reality of work under capitalism: the city is useful precisely to the extent that physical proximity to a range of services and labor makes sense to a particular business; the attraction of such places to those who need to find work has a well-documented trajectory, but one that is entirely contingent upon the presence of businesses whose decisions to locate in a particular place have to do only with calculations concerning profitability. Whether workers move to follow jobs, or capital moves to reduce its costs, has nothing to do with supporting a "more stable... community." "Community" is a historically-bounded and unintended consequence of urbanization, neither its driving force nor its inevitable result. The suburban Desperate Housewives have as much sense of community as the urban Friends. Of course, both of these examples are fictional, but no more so than the "community" imagined in this LEED credit.

Note that a business may need to locate in an urban area for reasons that have nothing to do with preserving greenfields or fostering "community," and there may be no impact on "community" or on the preservation of greenfields (i.e., the nature of such a business may preclude development outside of urban areas so that greenfields, in any case, were never threatened) as a result of such development, yet the LEED credit is still awarded.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Build in urban areas. To compute density: a) check project density (total building area divided by property or project site area) b) the density radius is 3 times the square root of the project site area (convert acres to square feet by multiplying by 43,560); c) add up building areas and site areas of all properties within the site area defined by the density radius; divide building area by site area to get site density.

5. Timeline and team.

6. Calculations. None

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Yes, if Option 1 is met and either the project itself has twice the density of the area within the density radius, or the average density within a doubled site area is 120,000 sq.ft. per acre.

10. Regional variations. N/A

12. Resources.

13. Definitions: building density = floor area/site area; greenfields are undeveloped sites including agricultural; mixed-use has combinations of residential, commercial or retail; neighborhood = residential area; pedestrian access means you can walk; previously developed sites were altered by humans; property area = all area within property lines; public transportation = bus, rail, etc.; residential area is zoned mainly for housing at 10 units/acre or more (so it excludes most suburban development); site area = property area.

SS Credit 3 Brownfield redevelopment (1 point)

Intent: Fix and develop environmentally damaged sites.

Requirements: Two options. Either (1) site is contaminated (per ASTM E1903-97 Phase II Environmental Site Assessment or local cleanup program) or (2) site is designated as brownfield by a governmental agency.

1. Benefits/issues. Makes the site better, plus takes pressure off undeveloped sites (greenfields). Lots of governmental intervention (incentives, reduced liability) available.

[From Version 2.2 critique] State intervention to protect profitability is mentioned here: The LEED commentary references CERCLA (the 1980 Comprehensive Environmental Response, Compensation, and Liability Act, a.k.a. the "Superfund") which funds governmental intervention to remediate contaminated sites; the use of "incentives" at all levels of government is also mentioned as a way of encouraging "brownfield redevelopment by enacting laws that reduce the liability of developers who choose to remediate contaminated sites." From this, it is clear that sustainable development often does not make economic sense to businesses without state intervention (where such intervention takes the form of subsidies or is directly legislated as a specific requirement).

2. Related credits. Yes.

3. Referenced standards. EPA brownfields definition; ASTM E152705 Phase I Site Assessment (no actual samples or analysis); ASTM E1903-97 Phase II Environmental Site Assessment (actually analyses soil, groundwater, materials, often after a Phase I assessment points to potential issues).

4. Implementation. Numerous techniques are available for water and soil treatment.

5. Timeline and team.

6. Calculations. None

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: brownfield is property whose "use may be complicated by presence... of hazardous substance..."; CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act) or Superfund, 1980 act to clean up sites with hazardous wastes; in situ remediation = cleaning methods on the site itself that minimize site disturbance; RCRA (resource conservation and recovery act), 1976, gives EPA power to control hazardous wastes (and some other wastes as well); remediation = fixing (cleaning up); site assessment = site evaluation of possible contamination.

SS Credit 4.1 Alternative transportation -- public transportation access (6 points)

Intent: Discourage use of cars (both from standpoint of pollution and sprawl).

Requirements: Two options. Either (1) have building entrance within 1/2 mile walk of commuter-type rail system; or (2) have building entrance within 1/4 mile walk of 2 bus lines.

1. Benefits/issues. Conventional critique of sprawl.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Find an appropriate site.

5. Timeline and team.

6. Calculations. Measure walking distances (e.g., < href="http://www.gmap-pedometer.com">http://www.gmap-pedometer.com)

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Two options. Either (1) 1 point max. for the entire Credit 4 suite for creating a "transportation management plan" to reduce car use; or (2) find a site within 1/2 mile of 2 commuter-type rail lines or within 1/4 mile of 4 bus lines, AND demonstrate that frequency of service is at least 200 transit rides a day (total).

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: attendance boundary is a school-related term; campus or private bus is not a public service; mass transit = bus, train; pubic transportation = open to public and providing more or less regular and continual service; walking distance is measured along walkable path.

SS Credit 4.2 Alternative transportation -- bicycle storage and changing rooms (1 point)

Intent: Discourage use of cars (both from standpoint of pollution and sprawl).

Requirements: Depends on project occupancy. For commercial/institutional projects: provide bike racks/storage for 5% of peak building users within 200 yards of entrance, along with shower/changing facilities for 0.5% FTE building occupants also within 200 yards (or, of course, within building itself). For residential projects: covered bike storage facilities for 15% occupants.

1. Benefits/issues. Reduces pollution, energy use, need for infrastructure. Health benefits.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation.

5. Timeline and team.

6. Calculations. As described above, but assume 2 residents per 1-BR unit; 3 per 2-BR unit, and so on. FTE of 1.0 is based on a single 8-hr occupant.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. 1 point max. for the entire Credit 4 suite for creating a "transportation management plan" to reduce car use.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: bicycle rack (anything that holds a bike in storage); FTE (full-time equivalent) is a 40-hour/week person; secure bicycle storage can be inside or outside; transient users do not use facilty regularly, e.g., customers in a retail store.

SS Credit 4.3 Alternative transportation -- low-emitting and fuel-efficient vehicles (3 points)

Intent: Discourage use of cars (both from standpoint of pollution and sprawl).

Requirements: 4 options. Either (1) provide so-called preferred parking (close to entrance or subsidized with 20% discount) for 5% spaces for low-emitting fuel-efficient cars [LEFE cars include ZEV (zero emissions), or have green score of 40 on American Council for an Energy Efficient Economy rating guide]; or (2) provide alternative-fuel stations for 3% spaces; or (3) provide LEFE cars and preferred parking for 3% FTE occupants; or (4) create LEFE vehicle-share plan (1 LEFE car per 3% FTE occupants; but since 1 car supports 8 FTE occupants, need only 1 car per 3/8% FTE occupants = 1 car per 267 FTE occupants).

1. Benefits/issues. Reduces pollution, energy use.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation.

5. Timeline and team.

6. Calculations. As described above.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. 1 point max. for the entire Credit 4 suite for creating a "transportation management plan" to reduce car use.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: alternative-fuel vehicles = cars using electricity, hydrogen, propane, compressed or liquid natural gas, methanol and ethanol, but also (in LEED) hybrids; fuel-efficient vehicles score 40 (see above); FTE as defined elsewhere; greenhouse gases =CO2, methane, CFCs; hybrid vehicles; low-emitting vehicles are classed as ZEVs; preferred parking.

SS Credit 4.4 Alternative transportation -- parking capacity (2 points)

Intent: Discourage use of cars (both from standpoint of pollution and sprawl).

Requirements: There are 3 cases (non-residential, residential, and mixed-use), each with 2 or 3 options.

1. Benefits/issues. Reduces pollution, energy use, and (for parking lots specifically), stormwater runoff and heat island effect.

2. Related credits. Yes.

3. Referenced standards. Institute of Transportation Engineers, Parking Generation Study, 2003 (http://www.ite.org)

4. Implementation. Possibly apply for zoning variance if expected parking demand is lower than what zoning mandates; but don't overload neighborhood with the project's overflow parking.

5. Timeline and team.

6. Calculations. As described above.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. 1 point max. for the entire Credit 4 suite for creating a "transportation management plan" to reduce car use.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: carpool is more than 1 person in a car (shared driving); mixed-use is combination of residential and commercial or retail; preferred parking is defined above.

SS Credit 5.1 Site development -- protect or restore habitat (1 point)

Intent: Promote biological diversity on site through restoration of damaged sites or conservation of undamaged natural areas.

Requirements: There are 2 cases (greenfields or previously developed sites)

1. Benefits/issues. Vegetation restoration is good for stormwater management; biodiversity is just good (but the rationale for encouraging biodiversity is not developed here).

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Standard grass lawns (turf) are "monoculture" and do not count here, even if native. For sites with both greenfields and non-greenfields, meet the criteria in both Cases; but try not to develop the greenfield portion.

5. Timeline and team.

6. Calculations. As described above.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Yes, for protecting or restoring the greater of either 75% of the site (excluding footprint of building), or 30% of the whole site with approved vegetation.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: adapted plants (introduced) = introduced, but non-invasive and low maintenance; biodiversity = ecosystem, species, and genetic diversity of life; building footprint = perimeter of building plan; development footprint includes building, hardscape, roads, etc.; greenfields; invasive plants are nonnative and likely to cause harm, threatening biodiversity; local zoning; native (indigenous) plants are noninvasive and have been in the area for a while (since before colonization); open space area is either defined in zoning or, for LEED, equal to property area - development footprint; previously developed sites are previously developed, even if only graded or otherwise altered; LEED project boundary is entire property (for single buildings) or a portion of the site for a particular building (where there are more than 1); retention ponds store runoff to remove pollutants before release of the water, using either gravity or pumps, and being either always or sometimes filled with water.

SS Credit 5.2 Site development -- maximize open space (1 point)

Intent: Promote biological diversity on site through restoration of damaged sites or conservation of undamaged natural areas.

Requirements: There are 3 cases (open space set by zoning; no zoning; and zoning, but no open space requirements) plus some "exceptions" that apply in all cases.

For all cases in urban areas where SS Credit 2 has been earned: both green roofs and pedestrian-themed hardscape can be counted as open space; where hardscape is used, at least 25% of the open space still must be vegetated.

For all cases, wetlands or natural-looking ponds count if the slopes along their boundaries are no steeper than 1:4 and are vegetated.

1. Benefits/issues. Supports wildlife, insects, pollinators; reduces stormwater runoff and heat island effect.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Campus plans can allocate, and count, open space outside the actual project site. Green roof "construction" is discussed. For landscaping to be "bird-safe" put it within 3 ft. of perimeter, or far enough away so that it is not reflected in facade windows. Fritted glass, etc. also works.

5. Timeline and team.

6. Calculations. As described above.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Yes, by doubling required open space, but seems to preclude use of non-site "campus" open space for these extra credits.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: adapted plants; biodiversity; building footprint; development footprint; greenfields; invasive plants; local zoning; native (indigenous) plants; open space area; LEED project boundary.

SS Credit 6.1 Stormwater design -- quantity control (1 point)

Intent: Make the developed site work like the undeveloped site in terms of stormwater/hydrology: reduce or eliminate pollution and contaminants from runoff; increase infiltration of water on site.

Requirements: There are 2 cases (where existing imperviousness is either greater, or not greater, than 50%).

1. Benefits/issues. Reduces the pollution associated with stormwater runoff, as well as the sediment caused by erosion and the increased rate of flow associated with hardscape and compacted ground. In some cases, stormwater can be used for nonpotable uses (e.g., flushing toilets). Dense urban projects may have difficulty dealing with this issue.

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Best strategy is to reduce impervious surfaces; other techniques include harvesting stormwater (both irrigation and indoor uses - fire suppression, toilet, urinal flushing), building swales and retention ponds, using green roofs, and clustering development to minimize hardscape infrastructure. Note that for irrigation, pressurization may be needed (15 psi usual; whereas only 0.43 psi is created naturally per foot of elevation, so pumps may be required).

5. Timeline and team.

6. Calculations. For peak runoff loads, use "rational method" or NRCS method; for total runoff quantity, use US Natural Resources Conservation Service (NRCS) method. For harvesting, measure (equation 1) the volume of captured runoff (ft3), Vr = P x Rv x A / 12, where P = average rainfall event (in.), Rv = 0.05 + 0.009I (I being the ratio of impervious to total surface x 100), and A = the area of collection surface (ft2). Then measure (equation 2) the minimum drawdown rate (that is the rate at which the captured water must be released so as to make room for the design storm runoff to be captured), Qr (ft3/sec.) = storage tank capacity (ft3) / rainfall event interval (sec.). In this last equation, the rainfall event interval is the time expected between design storms, for example, 3 days = 259,200 sec. Using this number allows the storage tank to be emptied in 3 days before the next expected storm.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Nothing specific, but 1 credit is possible for performance much better than required.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: aquifer is underground geological formation carrying water; erosion; hydrology is the study of water in the ecosystem; impervious surfaces do not allow water to infiltrate (less than 50% pervious); retention ponds; stormwater runoff.

SS Credit 6.2 Stormwater design -- quality control (1 point)

Intent: Make the developed site work like the undeveloped site in terms of stormwater/hydrology: reduce or eliminate pollution and contaminants from runoff; increase infiltration of water on site.

Requirements: Make a plan to promote infiltration of stormwater on site, while treating at least 90% of annual rainfall using BPMs (best management practices) that remove 80% of annual TSS (total suspended solids) according either to state/local standards or based on accepted infield monitoring. Annual rainfall is at least 40 in./year (humid watersheds), between 20-40 (semiarid watersheds), or less than 20 (arid watersheds), which -- for this credit which requires treatment of 90% -- is equivalent to being able to treat the runoff from 1 in., 0.75 in., or 0.5 in. of rainfall respectively.

1. Benefits/issues. Typical runoff carries sediment and pollutants which have negative environmental impacts, as well as costs for infrastructure (pipes, treatment plants).

2. Related credits. Yes.

3. Referenced standards. N/A

4. Implementation. Nonstructural: make vegetated areas or use pervious pavement; pollutants are often then broken down naturally in the soil. Structural: cisterns, ponds, "manhole treatment devices" can remove pollutants, and may be required on small or urban sites. For such sites with more than 50% impervious surfaces, measures can include fixing storm sewers, or making separate storm and sanitary sewers where they have been combined. But the best strategy is to increase permeable surface areas, including green roofs.

5. Timeline and team.

6. Calculations. Depends.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Nothing specific, but 1 credit is possible for performance much better than required.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions: impervious surfaces; retention ponds; stormwater runoff;; total suspended solids (TSS) are particles of a size that lets them travel with the runoff rather than settling out naturally, and can be removed by filtration.

SS Credit 7.1 Heat island effect -- nonroof (1 point)

Intent: reduce heat islands

Requirements: 2 options. Either (1) shade 50% of hardscape with trees, solar panels, or other devices that reflect heat (SRI = solar reflectance Index of 29 min.), use hardscape materials with SRI >= 29 for 50% of hardscape; or use an open-grid pavement system that is at least 50% pervious; or (2) cover 50% of parking with solar panels, green roof, or materials with SRI >= 29. Solar panels, if used, must "offset some nonrenewable resource use."

1. Benefits/issues. There are two issues: elevated temperatures have a negative impact on indigenous ecosystems; also generally require higher energy use for cooling loads.

2. Related credits. Yes.

3. Referenced standards. Numerous ASTM standards for measuring how surfaces absorb heat, including ASTM E408-71(1996)e1, Standard Test Methods for Total Normal Emittance of Surfaces using inspection-Meter Techniques.

4. Implementation. Various material SRI values given in Table 1, including gray concrete (35), white concrete (86), and old gray concrete (19). Asphalt has an SRI of 0 (9 if weathered). Avoid glare issues. plantings must be adequate within 5 years. Consider bird collisions when placing vegetated shading near glazing.

5. Timeline and team.

6. Calculations. Area shaded is the average of 10am, 12 noon, and 3pm on summer solstice. SRI values can be taken from Table 1, or computed using emissivity and solar reflectance according to ASTM standards. If a surface is covered or shaded in more than one way, it still only counts once.

For option 2 [from Implementation]: "no SRI requirement for parking that is underground, under a deck, or under a building as long as any exposed parking surface area is 50% or less of the total parking surface area." This seems to be in contradiction to the requirement that 50% of parking be covered with materials having SRI >= 29 (or the other shading options).

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Yes, by going to 100% for either option 1 or 2.

10. Regional variations: note that this seems valid only in climate zones 1, 2, and 3 (per ASHRAE 90.1-2007).

11. Operations/maintenance.

12. Resources.

13. Definitions: emissivity is radiation emitted by a surface / radiation emitted by black body at same temperature; greenhouse gases; hardscape = stone, concrete, brick paths, roads, patios, etc.; heat island effect; impervious surfaces; infrared (or thermal) emittance is about 0.9 for most building materials (on a scale of 0 to 1 where 1 is total emittance of heat) -- shiny metals, though, have low emittance; open-grid pavement has vegetation within the impervious grid and is less than 50% impervious; perviousness allows water to infiltrate into the ground; solar reflectance (albedo) measures reflectance of visible, infrared, and ultraviolet on a scale of 0 (black) to 1 (white paint); SRI (solar reflectance index) measures the material's "ability to reject solar heat) on a scale of 0 (standard black) to 100 (standard white). Actually, it's possible for a material to be less than 0 or more than 100; undercover parking is under something like a roof, deck, or ground and any hardscape cover is shaded (or has an SRI >= 29?).

SS Credit 7.2 Heat island effect -- roof (1 point)

Intent: reduce heat islands

Requirements: 3 options. Either (1) use roofing with SRI = 78 for low-sloped roofs and SRI = 29 for steep-sloped roofs (> 2:12) over 75% of the total roof surface (or less than 75% if actual/required SRI compensates); or (2) make a green roof for 50% of the roof area; or (3) use some combination of options 1 and 2 such that 1-1/3 times the SRI-compliant area plus 2 times the green roof area equals or exceeds the total roof area. See calculations for details.

1. Benefits/issues. There are two issues: elevated temperatures have a negative impact on indigenous ecosystems; also generally require higher energy use for cooling loads. Plus, green roofs provide habitat for birds, bugs, etc.

2. Related credits. Yes.

3. Referenced standards. Numerous ASTM standards for measuring how surfaces absorb heat, including ASTM E408-71(1996)e1, Standard Test Methods for Total Normal Emittance of Surfaces using inspection-Meter Techniques.

4. Implementation. Various roofing material SRI values are given in Table 1, including gray EPDM (21), gray asphalt shingles (22), and white PVC (104). Green (vegetated) roofs typically consist of a number of layers including (from top down) the vegetation itself in a "growing medium" such as soil; filter fabric to keep the soil particles from clogging the drainage/water storage layer immediately below; insulation; root barrier to protect the roof (waterproof) membrane from damage; and finally some sort of roof substrate (deck, slab). Watch out for bird collisions. use native/adapted plants. If irrigation is required, try to use harvested water. Area-weighted SRIs can be used to accommodate low-reflectance pavers within green roofs (see definitions).

5. Timeline and team.

6. Calculations. In computing roof area, do not count areas with mechanical equipment, or solar panels. The basic criterion covering all 3 options can be re-written as follows:

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Yes, by having 100% green roof area (not counting mech./solar panel areas).

10. Regional variations: note that this seems valid only in climate zones 1, 2, and 3 (per ASHRAE 90.1-2007).

11. Operations/maintenance.

12. Resources.

13. Definitions: area-weighted SRI (e.g., to accommodate pavers within green roofs) shows SRI equivalent to a hypothetical roof with SRI of 78 (over 3/4 of the area) and SRI of 30 (over the remaining area); emissivity; greenhouse gases; hardscape; infrared emittance; albedo; SRI.

SS Credit 8 Light pollution reduction (1 point)

Intent: reduce light trespass, sky-glow, glare, and impact on nocturnal ecosystems.

Requirements: satisfy one of the 2 options for interior lighting AND the requirement for exterior lighting.

1. Benefits/issues. Yes, safety is important (exterior lighting at night), but it is possible to minimize the negative impacts through careful design.

[From Version 2.2 critique] The recommendations for low-reflectance surfaces (to minimize light pollution) contradict the recommendations in Credit 7 (Heat Island Effect) for high-reflectance surfaces. There is no attempt at resolution.

2. Related credits. Yes.

3. Referenced standards. ANSI/ASHRAE/IESNA Standard 90.1-2007 (include errata, not addenda) where ANSI = American National Standards Institute; ASHRAE = American Society of Heating, Refrigerating, and Air-Conditioning Engineers; and IESNA = the Illuminating Engineering Society of North America. This is the general standard for energy-efficient building design (non-lowrise-residential), and contains sections relevant to other LEED credits elsewhere; the relevant section here is Section 9 of the Standard (Lighting) and, in particular, only the requirements for exterior lighting apply to this LEED credit. Lighting power densities for building exteriors from the Standard are reproduced as Table 3 (changed to Table 1 in addenda online). For example, building facades are limited to 0.2W/ft2 per wall or surface, or 5.0W/linear foot; whereas drive-through windows are limited to 400W per drive-through (fast-food). These are "non-tradable," whereas others (e.g., walkways) have requirements that can be "traded" so that overall totals are met.

4. Implementation. Interior lighting: (1) timers that turn off lights after business hours do not apply to buildings with 24-hour operation; such facilities must use the second option 2. Exterior power density: so-called curfew timers are fine (shutting off exterior lighting at a pre-determined time), but lights must still meet standards in their "pre-curfew" mode. In general, two lower-level luminaires are better than a single high-powered luminaire.

5. Timeline and team.

6. Calculations. None for interior lighting. For exterior lighting, follow the Standard. Note that the measure of wattage is the input, rather than the lamp, watts (i.e., including power lost in the ballasts, etc.).

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A.

10. Regional variations. N/A.

11. Operations/maintenance.

12. Resources.

13. Definitions: curfew hour = 10:00 pm unless there are local restrictions; footcandle (fc) measures the amount of light on a surface and equals the light on 1 ft2 from 1 candela source 1 ft. away, or 1 lumen per ft2; full-cutoff luminaire has 0 candela intensity above 90 degrees, and candela/1000 lamp lumens is no greater than 100 (i.e., 10% fo the lamp lumens) at 80 degrees; horizontal footcandle; light pollution; light trespass; safety and comfort light levels; sky glow; vertical footcandles.

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