Add "skylights" to the list of things deducted from the roof area so that the sentence reads, "Determine the area of the roof covered by mechanical equipment, solar energy panels, skylights, and other appurtenances, and deduct these areas from the total roof surface area."
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Credit language
© Copyright U.S. Green Building Council, Inc. All rights reserved.
Intent
To reduce heat islands1 to minimize impacts on microclimates and human and wildlife habitats.
Requirements
Option 1
Use roofing materials with a solar reflectance index (SRI)2 equal to or greater than the values in the table below for a minimum of 75% of the roof surface. Roofing materials having a lower SIR value than those listed below ay be used if the weighted rooftop SRI average meets the following:|
Area Roof Meeting Minimum SRI ———————————————— Total Roof Area |
x |
SRI of Installed Roof —————————— Required SRI |
≥ |
75% |
OR
Option 2
Install and maintain a vegetated roof that covers at least 50% of the roof area.OR
Option 3
Install high-albedo and vegetated roof surfaces that, in combination, meet the following criteria:|
Area Roof Meeting Minimum SRI ———————————————— 0.75 |
+ |
Area of Vegetated Roof —————————— 0.5 |
≥ |
Total Roof Area |
|
Roof Type |
Slope |
|
|
Low-sloped roof |
≤ 2:12 |
78 |
|
Steep-sloped roof |
> 2:12 |
29 |
1 Heat islands are defined as thermal gradient differences between developed and underdeveloped areas.
2 The solar reflectance index (SRI) is a measure of the constructed surface's ability to reflect solar heat, as shown by a small temperature rise. It is defined so that a standardblack surface (reflectance 0.05, emittance 0.90) is 0 and a standard white surface (reflectance 0.80, emittance 0.90) is 100. to calculate the SRI for a given material, obtain the reflectance value and emittance value for the material. SRI is calculated according to ASTM E 1980. Reflectance is measured according to ASTM E 903, ASTM E 1918, or ASTM C 1549. Emittance is measured according to ASTM E408 or ASTM C 1371.
3 For the purposes of this credit, under cover parking is defined as parking underground, under deck, under roof, or under a building.
Credit substitution available
You may use the LEED v4 version of this credit on v2009 projects. For more information check out this article.What does it cost?
Cost estimates for this credit
On each BD+C v4 credit, LEEDuser offers the wisdom of a team of architects, engineers, cost estimators, and LEED experts with hundreds of LEED projects between then. They analyzed the sustainable design strategies associated with each LEED credit, but also to assign actual costs to those strategies.
Our tab contains overall cost guidance, notes on what “soft costs” to expect, and a strategy-by-strategy breakdown of what to consider and what it might cost, in percentage premiums, actual costs, or both.
This information is also available in a full PDF download in The Cost of LEED v4 report.
Learn more about The Cost of LEED v4 »Frequently asked questions
We’re working on an international project and having a hard time finding a coating with a published value for Solar Reflectance Index. If the coating is white, can we assume that it qualifies?The answer to this question is available to LEEDuser premium members. Start a free trial » (If you're already a premium member, log in here.) |
Are solar panels always excluded from the roof area for the purposes of the credit calculations?The answer to this question is available to LEEDuser premium members. Start a free trial » (If you're already a premium member, log in here.) |
Why does the form calculate my high-albedo roof area, as a value greater than 100% of total roof area?The answer to this question is available to LEEDuser premium members. Start a free trial » (If you're already a premium member, log in here.) |
What needs to be included in the roof maintenance program?The answer to this question is available to LEEDuser premium members. Start a free trial » (If you're already a premium member, log in here.) |
Addenda
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Below equation, add the text and equation:Alternatively, the following equation may be used to calculate compliance:(see image)
Campus Applicable
No
Internationally Applicable:
No
10/1/2012 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In the second sentence, delete "Particularly in urban areas"; revise the last clause so that it reads, "Other sources may include vehicle exhaust, air-conditioners, and street equipment. Reduced airflow because of tall buildings and narrow streets exacerbate the effect."
Campus Applicable
No
Internationally Applicable:
No
7/6/2012 – Updated: 2/14/2015
Global ACP
Description of change:
Delete the Note for Projects Outside the U.S.
Campus Applicable
No
Internationally Applicable:
Yes
8/1/2011 – Updated: 2/14/2015
Rating System Correction
Description of change:
Below equation, add the text and equation:Alternatively, the following equation may be used to calculate compliance:(see image)
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Replace the term "photovoltaic panels" with "solar energy panels" and add "other appurtenances" to the list of things deducted from the roof area so that the sentence reads "Projects may earn an Innovation in Operations (IO) credit for exemplary performance by demonstrating that 95% of the project\'s roof area (excluding any mechanical equipment, solar energy panels, skylights, and other appurtenances) consists of a vegetated roof system."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In alphabetical order, add the term, "Roof area is the area of the uppermost surface of the building which covers enclosed Gross Floor Area, as measured when projected onto a flat, horizontal surface (i.e. as seen in Roof Plan view). \'Roofs\', or portions of roofs, covering unenclosed areas (e.g. roofs over porches and open covered parking structures) are not included in the areas used to evaluate compliance with SSc7.2, though they may be applicable to SSc7.1."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Below equation, add the text and equation:Alternatively, a weighted average approach may be used to calculate compliance for multiple materials:(see image)
Campus Applicable
No
Internationally Applicable:
No
10/1/2012 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Replace the definition of "solar reflectance (SR)" with "the fraction of solar energy that is reflected by a surface on a scale of 0 to 1. Black paint has a solar reflectance of 0; white paint (titanium dioxide) has a solar reflectance of 1. The standard technique for its determination uses spectrophotometric measurements, with an integrating sphere to determine the reflectance at each wavelength. The average reflectance is then determined by an averaging process, using a standard solar spectrum, as documented by ASTM Standards E903 and E892."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In alphabetical order, add the term "An appurtenance is any built-in, nonstructural portion of a roof system, such as skylights, ventilators, mechanical equipment, partitions, and solar energy panels."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Rating System Correction
Description of change:
Below equation, add the text and equation:Alternatively, a weighted average approach may be used to calculate compliance for multiple materials:(see image)
Campus Applicable
No
Internationally Applicable:
No
6/19/2008
LEED Interpretation
Inquiry:
Our project uses three different roof systems that contribute to minimizing the heat island effect. Due to the complexity of the roof on this project, calculation of LEED NCv2.2 Credit 7.2 is not entirely clear, as the reference guide offers two formulas for addressing multiple roofing types. Additionally, the building is under an historic preservation easement in the City of Pittsburgh that requires that the pitched roof portion of the building that is visible to the street and passersby be either restored to its original construction, dark slate, or to its most recent construction, asphalt shingles. The first roof system is a vegetative roof that comprises 1,424 sq ft of roof area. The second roof system is a flat roof with a PVC membrane with an SRI of 104 and covers 1,250sqft. The third roof is a steep sloped roof that for the historical reasons above has a faux slate product with an SRI of 8 and covers 1,680sqft. The total roof is 4,354sf, of which 39% is comprised by the historic roof. Due to the number of roofing systems on this project and their differences, no single equation from the LEED NCv2.2 Reference Guide will allow us to appropriately determine the net effect the total roof has on the urban heat island effect. By combining two of the compliance paths already determined by the LEED NCv2.2 reference guide it may be possible to determine one compliance path to cover one project regardless of the complexity of the roof. The reference guide gives four possible compliance paths: Option 1: 75% of the roof surface is required to meet the minimum SRI value for a particular roof type (Area of SRI roof/0.75)>=Total Roof Area Option 2: Vegetative roof is at least 50% of the total roof area (Area of Vegetated Roof/0.5)>= Total Roof Area Option 3: Combine Option 1 and 2 (Area of SRI roof/.75)+(Area of Vegetated Roof/0.5)>=Total Roof Area Option 4: Referenced in the Calculations Section, Weighted averaging to show that the total theoretical roof does comply (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...>=Total Roof Area To show that the proposed roof of this project does comply with the intent of this credit, the two equations needed would be from \'Option 2\' and \'Option 4\'. The precedent for combining these two calculations comes from \'Option 3\'. Our interpretation on combining different compliance paths is that they can be added together as long as the areas in each equation are independent of one another so that any area on the roof cannot be counted more than once. We propose the following equation for a roof consisting of a vegetative roof along with two or more other roofing systems: (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...+(Area of Vegetated Roof/0.5)>=Total Roof Area For this and other projects using multiple roof constructions, does the above calculation meet the intent of the credit, and will this be considered an additional path of compliance? Also, is it possible to exclude historic roofs from SS7.2 calculations?
Ruling:
The CIR is requesting clarification on the appropriate formula to use when calculating SSc7.2 compliance for multiple roof materials in addition to vegetated roof area. The project is also requesting permission to exclude roof areas which are subject to historical preservation requirements from the credit calculations. The project may use the following formula to calculate credit compliance for multiple materials including vegetated roof areas: [(Area of Roof A*(SRI of Roof A/Required SRI)) + (Area of Roof B*(SRI of Roof B/Required SRI)) / 0.75] + [ Area of Vegetated Roof/0.5] >= Total Roof Area Historical Roof Areas may not be excluded from the calculations. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
11/1/2011
LEED Interpretation
Inquiry:
There is a stainless steel tube veil that covers the complete building. The tubes are placed with a 1 mm spacing between each other, and the material interior cannot be seen. Therefore, we would like to conduct a test to verify if the SRI of the tubes will comply with the LEED requirements (equal or greater than 78). Due to the originality of the exterior facade, we would like to know what type of test should be conducted:
Option 1 - Test using a 4mx4m mock up of the roof assembly and test the reflectance per ASTM 1918,
Option 2 - A flat sample test of all the materials installed on the roof
Please advise if there are any other tests that would need to be conducted.
Ruling:
The Referenced LEED Standard of ASTM 1918-97 has been superseded by ASTM 1918-06. For a roof with a veil design, or similar non-homogenous materials, the project should perform a SRI test to ASTM E1175 - 87(2009) Standard Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere. When submitting for LEED Certification, please include a copy of this interpretation and a summary of any testing results that document the SRI rating for the installed veil surface.Projects may wish to test any mock-up to assess credit compliance before testing installed materials, but the testing for certification should be done for the installed roofing assembly. Applicable internationally.
Campus Applicable
No
Internationally Applicable:
Yes
9/5/2008
LEED Interpretation
Inquiry:
In an effort to reduce heat islands, the car park for this hotel project is covered. All of the building car park is at ground level (there is no basement). The car park cover is made up of both the hotel building and a podium area that extends out from the hotel. The roof area includes: Podium Roof: 1. Green roof area - 394m2 2. Hardscaped area - 832m2 (The hardscaped area is in two parts. An area on one side of the building for pedestrian use and an area at the rear of the building which contains a vehicular ramp where cars will drive over the corner of the site) 3. Total podium roof area (1+2) = 1226m2 Building Roof: 4. Total footprint (including stairs & plant) - 1084m2 5. Total footprint (excluding stairs & plant) - 836m2 Can the podium roof (including the green roof) be included in the total roof surface for this project?
Ruling:
The podium deck, which covers on-grade parking, cannot be considered a roof area for the purposes of this credit. CIR Ruling dated 9/24/2001 rules that the top deck of an above-grade parking structure is to be considered non-roof impervious area. If the podium deck covered conditioned space, then the deck could be considered as a roof (for portions not being used for parking). Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/1/2012
LEED Interpretation
Inquiry:
Can helipads and other functional space areas be exempted from SSc7.2 Heat Island Effect- Roof calculations?
Ruling:
Roof area that consists of functional, usable spaces- such as helipads, recreation courts, and areas covered by equipment, solar panels, and appurtenances- can be exempted from the roof calculations for SSc7.2. Projects are not eligible for SSc7.2 if the exempted spaces encompass the entire roof area. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
9/20/2004
LEED Interpretation
Inquiry:
Our building has a flat roof membrane which is specified to comply with all requirements of this Credit. However, as part of our approval process the County also required, purely for aesthetics, a free-standing curved roof canopy which stands over some mechanical equipment but which mainly stands over and actually shades much (~40%) of the actual roof membrane. This curved roof canopy system does not directly connect to the building envelope except at its column bases and has a free flow of air between it and the roof membrane. As such, our question is whether this freestanding curved roof canopy material (which is currently specified as painted metal, but which may also be a membrane material) must be counted in the 75% of available roof area required by this Credit to achieve both Energy Star reflectance criteria (which it actually does) and emissivity (for which it has not been tested using ASTM E408).
Ruling:
The canopy is effectively part of the roofing system as it relates to reflectivity and should be included in calculations for this credit. Please refer to SSc7.2 CIR ruling dated 3/11/2003 for further guidance. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
1/23/2006
LEED Interpretation
Inquiry:
Previous CIRs have allowed the use of a weighted average approach for the reflectance and for the emissivity of a roof material. A baseline reflectance is calculated by applying the minimum reflectance of the roof (0.65) and multiplying it by the percentage of roof it covers (75%). This calculation results in a baseline reflectance of 0.4875. Similarly, baseline emissivity can be calculated as 0.90 x 75% = 0.675. Can this weighted average approach be used for both of these values simultaneously? In other words, if a roof material covers 100% of the roof area, and its reflectance is 0.4875 or greater, and its emissivity is 0.675 or greater, does it meet the credit requirements? Will the weighted average approach also be allowed as it pertains to a roof\'s SRI under v2.2?
Ruling:
Per the CIR Ruling for SSc7.1 dated 12/05/01, you may perform a weighted average calculation for the reflectivity. Alternatively, you may apply the weighted average for emissivity instead of reflectivity, but not both (it would be too lenient compared to the original credit requirements). The weighted average approach can be used for SRI in NC v2.2. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/11/2007
LEED Interpretation
Inquiry:
Our project contains low slope roof, steep slope roof, and vegetative roof conditions. All specified roof products meet requirement for EMITTANCE of .90 or greater based on ASTM E408-71. Project will need to perform a "Weighted Average" to attain required SOLAR REFLECTANCE. Due to steep slope roofs, low slope roofs, and vegetative roofs having different requirements for reflectance I am assuming when considering the weighted average base on "CIR SS7.1 12/5/2001" these three are to be considered separately. We have specified adhered membrane roof (energy smart light grey) (solar reflectance = .49) in both steep slope and low slope conditions, vegetative roof area (low slope), and recycled synthetic shake shingle (steep slope) (solar reflectance = .18). Low Slope Roof Required (6%): (75% x .65) = .4875 Actual Low Slope (adhered membrane) (100%): .49 Steep Slope Roof Required (59%):(75% x .25) = .1875 Actual Steep Slope (Recycled Shake Shingle 75%): .18 Actual Steep Slope (adhered membrane 25%): .49 Actual Average: .75(.18) + .25(.49) = .25 Vegetative Roof (35%) We also need clarification of interpretation of Solar Reflectance Value determined for the specified Recycled Shingle. Specified product is designed to lighten up and grey as part of its natural weathering process. Product pulled off of production line does not meet required values for reflectance. However, ASTM E903 tests performed after just 6 months of weathering indicated an average tested solar reflectance of .18. This value falls with-in the allowed weighted average to attain the point. This product also tested at .15 after three years which also passes Energy Star guidelines with out considering weighted average. We feel that using the 6 month weathered values for solar reflectance should be considered in this case due to the fact that our specified product attains required value after only 1% of its warrentied life (considering it has a 50 year unconditional transferable warranty and a 100 year life expectancy). Please comment as to whether the above assumptions are consistent with your intent for credit SS7.2 Reduce Heat Island (Roof) and will or will not attain credit. Thank you.
Ruling:
The methodology noted in SSc7.1 CIR Ruling dated 12/5/2001 is appropriate to demonstrate compliance with SSc7.2. The "weighted average" methodology when applied to the roofing materials used on low slope and steep slope conditions can provide teams with an alternative method for achieving this credit. It appears from the values above that this project would meet the credit requirements set forth and referenced in the EPA Energy Star Roofing Guidelines. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/17/2007
LEED Interpretation
Inquiry:
Since SSc7.2 roof area calculations exclude skylights, parapets, equipment, paving, and other rooftop surfaces ineligible for EnergyStar consideration, we question whether the translucent tensile fabric structure covering portions of our Project qualifies as "roof" in SSc7.2 calculations. For our Project, the proposed fabric roof covers unconditioned outdoor space, but the same questions may apply on projects using similar products to enclose conditioned interiors. The manufacturer of the proposed tensile fabric system claims that their membrane meets EnergyStar reflectivity requirements and that they are pursuing California Cool Roof and EnergyStar ratings. On this basis, we included this area in our initial roof area calculations. However, the manufacturer has not submitted conclusive evidence supporting their claim. We received ASTM E408 test reports confirming their product\'s emissivity, but submittals have referenced ASTM E424 reflectivity tests, not the ASTM E903 & C1549 tests cited in EnergyStar\'s Eligibility Criteria. The manufacturer asserts that ASTM E424 test for visible light reflectivity is equivalent to E903. They have only submitted data for new materials, but they have not complied with EnergyStar\'s aged testing requirements. SSc7.2 Credit Requirements specifically refer to EnergyStar Eligibility Criteria and ASTM E903 tests for solar reflectance, noting that visible reflectance is irrelevant to Credit compliance. Past CIRs emphasize the requirement for aged testing and the need for all testing to conform to the specific, cited ASTM methods. However, these tests may be inapplicable to translucent materials, and such materials may not even qualify as "roofs" under EnergyStar Eligibility Criteria. EnergyStar\'s Eligibility Criteria define "roof surface" as, "The uppermost part of the roof system that is in direct contact with solar radiation", yet their list of "Qualifying Products" does not include light-transmitting roof materials such as glass, plastic, fiberglass, or fabric. All roof types defined in the Criteria appear to be opaque membranes, coatings, tiles, and shingles applied directly to structure. Both cited reflectivity tests, ASTM E903 and C1549, apply primarily to opaque membranes, referring to other test methods for translucent materials. [Measurements of reflectivity and emissivity alone may not accurately gauge heat-island effect at clear or translucent materials. Opaque roofs can only reflect solar radiation or convert it to heat. When considering translucent materials, one may need to deduct energy from transmitted light as well.] If the tensile structure counts toward our total Project roof area, but fails to achieve EnergyStar, one of the buildings on our campus will not meet the 75% EnergyStar/high-emissivity requirement. [All other buildings do comply, including the Main Building, whose EnergyStar roof makes up at least 87% of the total Project roof area. However, the Main Building\'s designer can only sign the Letter Template for his own scope. We had hoped that each building could comply independently, allowing each designer to sign SSc7.2 Letter Templates for each respective scope.] If we can exclude the tensile roof from the total Project roof area, all buildings will clearly comply. Can we omit light-transmitting materials, such as those described above, from SSc7.2 roof area calculations as we would skylights? If not, what tests, applicable to light-transmitting materials, will demonstrate EnergyStar equivalence of such materials? Finally, if one of our three Designer\'s scopes cannot demonstrate Credit compliance, can the Project still achieve the Credit based on Letter Templates from the remaining Designers?
Ruling:
While Energy Star defines a roof surface as "the uppermost part of the roof system that is in direct contact with solar radiation," based on the description of the tensile fabric canopy system, it does not appear that the system meets the definition of a roof. The credit\'s testing standards (Energy Star\'s Program for Roof Products) focus on systems and/or products that are considered permanent, primary systems whose sole function is to shelter the elements, e.g. rain, snow, wind, etc. from entering the building. The project team describes their fabric system as covering unconditioned outdoor space, not a building. Thus, it is acting as a shade structure. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/27/2009
LEED Interpretation
Inquiry:
Our project comprises a commercial office tower with an associated podium for carparking. As part of the architectural design, a non-load bearing laminated glass canopy will be constructed from the main office tower and extend over the ground floor public plaza. The canopy will also partly cover the podium. The top deck of the podium will be carparking, and therefore the canopy will in park cover this carparking. Please can you confirm whether this glass canopy should be considered as a \'roof\' under SS-C7.2, and as a glass structure whether it should be exempt from SRI calculations?
Ruling:
Yes, the glass canopy can be excluded from SRI roof requirements under SSc7.2 as it covers an unconditioned outdoor space, not a building. Per NCv2.2 SSc7.1 CIR ruling dated 2/14/2008, the glass canopy can be excluded from SRI requirements under SSc7.1 if parking is placed underground or under deck, so long as the exposed parking area is less than or equal to 50 percent of the total parking surface. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
8/1/2011
LEED Interpretation
Inquiry:
Many of the ASTM Standards we reference have been withdrawn, upgraded, or superseded. Provide guidance on which updated standards should be used.
Ruling:
The withdrawn ASTM Standards listed- ASTM E1980-01 and ASTM E903-96- are still the correct references for SSc1: Site Selection, SSc7.1: Heat Island Effect, Non-Roof, and SSc7.2: Heat Island Effect-Roof. These two standards were not withdrawn for technical reasons, but were withdrawn because they had not been updated within 8 years. Testing can still be performed for these as well as the superseded standards. The updated versions of the superseded standards can be used, but are not required:Old: ASTM E408-71(1996), Current: E408-71(2008)Old: ASTM C1371-04a, Current: C1371-04a(2010)Old: ASTM E1918-97, Current: E1918-06 Old: ASTM C1549-04, Current: 1549-09Note: This Interpretations is also applicable to Sustainable Sites Credit 7.1: Heat Island Effect- Non-Roof and Sustainable Sites Credit 1: Site Selection, see LEED Interpretations dated 8/1/2011 ID number 10092 and 10094 respectively. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/2/2008
LEED Interpretation
Inquiry:
Many CIRs address the fact that you can use the weighted average method outlined in the SSc7.1 CIR dated 12/5/2001 for SSc7.2. That CIR outlined a baseline which assumed 30% of the site met the 0.3 reflectance requirement, and 70% did not. However, the NCv2.2 Reference Guide for SSc7.2 outlines a weighted average calculation which differs from the SSc7.1 method in two ways. The first is that the outlined baseline (75% w/ SRI of 78 & 25% w/ SRI of 30) requires that 100% of the roof area is compliant with the SRI requirements. Also, the outlined baseline assumes that 75% of the roof area is low sloped, and 25% is steep sloped. If a project has a low slope for 64% and a steep slope for 36% of the roof area, can we use a baseline weighted average which reflects our ratio of steep to low sloped roof? Also, can we use a baseline weighted average calculation which requires 75% of the roof area to be compliant instead of 100% of the roof area? I\'ve outlined an example below: If 75% of the low sloped roof is compliant, for our project this would mean 48% (64%x0.75) of the total roof area should have an SRI of at least 78. If 75% of the steep sloped roof is compliant, this would mean 27% (36%x0.75) of the total roof area should have an SRI of at least 29. Since 48% + 27% = 75% of the total roof area, this method reflects credit requirements and is consistent with the weighted average methodology outlined in the SSc7.1 CIR. Therefore, the weighted average baseline would be: 27% x 29 + 48% x 78 = 45.27 Can this calculation methodology be used to calculate the baseline for the weighted average option for SSc7.2?
Ruling:
Can a project use a weighted average calculation to show credit compliance? Yes, projects may use a weighted average calculation to achieve compliance equivalent to the required 75% threshold. As noted in v2.2 SSc7.2 CIR Ruling dated 6/19/2008, if the project applies for this credit under v2.2, the project may use the following formula to calculate credit compliance for multiple materials: [(Area of Roof A*(SRI of Roof A/Required SRI)) + (Area of Roof B*(SRI of Roof B/Required SRI)) / 0.75] + [ Area of Vegetated Roof/0.5] >= Total Roof Area In order for a project registered for v2.1 to apply for this credit using the v2.2 requirements, the project team must submit through LEED Online and follow the process outlined in the Credit Substitution Memo dated 12/19/2006 which can be found on the USGBC\'s website at: www.usgbc.org/ShowFile.aspx?DocumentID=1704 Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/1/2012
LEED Interpretation
Inquiry:
Can sidewalks, roads, and other hardscape areas located above a project building\'s underground parking structure, which are required by the governing municipality to be constructed of non-compliant materials, be excluded from the SSc7.2 and SSc7.1 calculations?
Ruling:
Similar to LEED Interpretations #2293 and #3101, sidewalks, roads, and areas that cover un-conditioned spaces (such as parking garages) are considered hardscape or landscape nonroof surfaces. Thus, they should be included in the calculations for SSc7.1 Heat Island Effect- Nonroof. In situations where infrastructure, materials, or surfaces are owned, operated and maintained by the local governing body, project teams may exclude the area of the material from the calculations for SSc7.2 and SSc7.1. This exemption can be applied only if projects do not have any control over the materials used for the surfaces in question. If the materials are owned and operated by the project, but the local jurisdiction specifies that they must meet certain criteria, the materials may not be excluded from the calculations. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
1/29/2009
LEED Interpretation
Inquiry:
The project is a multiple building (campus) submission, it is for 2 1/2 million square feet of office, amenity and associated support functions. The flat roofing type selected by the team for the majority of roof area is a Protected Roof Membrane assembly, which consists of a roofing membrane on the roof slab, covered by rigid insulation, which is then covered by medium weight (17-20 PSF) gravel ballast. The design and construction team was unable to find "white coated gravel" listed in the reference guide for light colored ballast that complies with SRI requirements for the point. The Oak Ridge National Laboratories published a four-year study of ballasted roofing assemblies that indicated that medium weight ballasted roofing systems performed as well or better than white roof systems for reducing the heat of the roofing membrane, and recommended that these systems be considered "cool roof" systems as well. The study also noted that these values were constant over a four year period, while the temperature reduction values for the white membrane roof degraded within the first year to a much lower value. We are aware that the study focused on the thermal performance of the system specifically related to heat transfer through the ballast to the membrane, but since the study showed that approximately the same (or less) heat got to the membrane than on a white (SRI compliant) roof at peak, we conclude that the rest of the heat is being rejected back into the air similar to the performance of the white roof. We spoke to the primary investigator on the study, Andre Desjarlais from ORNL, and he said the following: "What the ballast does is redistribute the temperature profile. Unlike a cool roof that simply reflects the solar load away, ballast stores the load and distributes it differently over the daily cycle." By using ballast, we are meeting the peak temperatures of the credit, although it is likely that we will end up with slightly higher temperatures emitting from the roof later in the day. The design team believes that this system, with its ability to dampen the temperature swings associated with a dark-colored roof, meets the intent of the LEED Credit. Can we consider this roofing system to meet the intent of the SS Credit 7.2 as an alternative method through performance? The study is called "Evaluating the Energy Performance of Ballasted Roof Systems" and was published in April, 2008. It is available at http://www.spri.org under "Technical Reports."
Ruling:
The CIR requests confirmation that a flat roofing type selected for the majority of roof area meets the intent of SS Credit 7.2 as an alternative method through performance. While the attributes of a flat roofing system using medium-weight ballast is shown by the ORNL study to have similar performance results for reducing cooling loads as a white cool roof system, that claim alone does not allow for an alternative compliance path for this credit. The intent of this credit relates to the microclimate of the surrounding area and its impact on local habitat. Cooling load comparisons only address the mechanical efficiency of the interior space of the project building. The ORNL study did not show an SRI of at least 78 for the ballast materials under study, which is required for this credit. Accordingly, this roofing system does not meet the intent of SS c7.2. The benefit of using a medium-weight ballast roof system might more appropriately be found in helping to achieve additional points toward EA Credit 1 - Optimize Energy Performance. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
12/5/2005
LEED Interpretation
Inquiry:
Our residential project is comprised of two multi-story towers that are connected on the ground floor with a single-story atrium that is sandwiched between the two towers. The sum of the two tower roofs equals 17,586 s.f. and makes up 70% of the total roof area. In order to comply with this credit and reduce heat islands, the two tower roofs are specified as a white TPO membrane that meets the emissivity and Energy Star requirements. We could easily achieve the credit requirement of 75% of the roof area by specifying white membrane for 1,254 s.f. of the 7,484 s.f. lower roof. However, in this case, we feel that having a high albedo lower roof would actually conflict with the intent of the credit. 97% of the curtain wall is glass, thus the towers would be subject to heat gain because the solar reflectance would project back up into the buildings. In addition, all of the residential units that face the atrium will have direct views of the roof which would expose the residents to glare. We propose to install a gray TPO membrane on the lower roof. This would not produce glare or contribute to as much heat gain as the white membrane, but still have a higher emissivity level than a standard black membrane. Given the circumstances, would you award us credit if the upper roofs are white and the lower roof is gray?
Ruling:
Per the CIR Ruling for SSc7.1 dated 12/05/01, you may perform a weighted average calculation for the reflectivity. Alternatively, you may apply the weighted average for emissivity instead of reflectivity (but allowing both would be too lenient). For example, the reflectance minimum weighted average can be calculated by applying the minimum reflectance of the roof (.65) and multiplying it by the percentage of roof coverage required (75% min.). This calculation results yields a baseline reflectivity average of 0.4875. For this example, each surface must comply with the emissivity requirement independently. If the average reflectance for your total roof area are above the minimum weighted averages, the overall criteria would be satisfied. NOTE: depending on the building orientation, reflection off the curtain walls could result in significant heat gain to the single story atrium. You might consider integrating a green roof over the single story atrium which would provide a pleasant view for the residents, eliminate the glare issue, and meet the intent of the credit.
Campus Applicable
No
Internationally Applicable:
No
9/24/2001
LEED Interpretation
Inquiry:
The parking for this project is a parking structure adjacent to the office building which is approximately equal in area to the "roof area" of the building. Is the upper deck of the parking structure to be a "roof" and therefore to be included in the total quantity of roof surface for this project? If so, is it necessary that an Energy Star high-reflectance and high emissivity coating be applied to the upper deck of the parking structure?
Ruling:
The upper deck of a parking garage is considered a non-roof impervious surface. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/11/2007
LEED Interpretation
Inquiry:
The project is a 43 acre urban development with 8 primary buildings containing roughly 17,000,000 s.f. of space. The LEED documentation for this project will be submitted concurrently as 8 separate submittals, one for each building; however, certain SS and WE credits will be submitted as campus credits as they pertain to the project at large. We are requesting approval to submit SSc7.2 as a campus credit since the SRI requirements have been calculated, and exceeded on a project-wide level. The weighted average roof calculation method described on page 98 of the LEED v2.2 Reference Guide was used to calculate a total weighted SRI of 84 for the project, which exceeds the theoretical SRI of 66 (75% of roof area = SRI 78 and 25% of roof area = SRI 30). In fact, 82% of the total campus roof area has an SRI that exceeds the theoretical SRI value of 66. The following weighted average calculation approach was used to determine the project-wide weighted SRI for all roofing surfaces: (Area of Roof Surface A / Total Campus Roof Area) * SRI of Roof Surface A) + (Area of Roof Surface B / Total Campus Roof Area) * SRI of Roof Surface B) + (Area of Roof Surface C / Total Campus Roof Area) * SRI of Roof Surface C) = Total project-wide weighted SRI Similar to other campus credits, the heat island effect is of campus-wide concern since the ambient air temperature around and above the development is directly affected by the albedo of selected roofing surfaces. By exceeding the SRI requirements for this credit on a campus-wide level, the heat island effect and associated cooling energy loads have been minimized, therefore promoting a healthier environment for the humans and wildlife that inhabit this development. We request confirmation that the proposed strategy to submit SSc7.2 as a campus credit is acceptable to achieve the intent of this credit.
Ruling:
The applicant is seeking to submit this credit based on a campus-wide aggregate of all the roof surfaces and corresponding SRI values. However, based on the LEED-NC Application Guide for Multiple Buildings & On-Campus Projects (AGMBC), which deals with campus situations like this, this approach is not acceptable for LEED projects to demonstrate individual achievement through weighted averaging of achievement across multiple LEED projects. The AGMBC does allow multiple buildings to submit as a single LEED project, for which the weighted average approach described above would be appropriate.Update April 15, 2011: Please note that all 2009 projects in multiple building situations must follow the 2010 Application Guide for Multiple Buildings and On-Campus Building Projects, located here: https://www.usgbc.org/ShowFile.aspx?DocumentID=7987. 2009 project teams should check this document for up to date guidance on all multiple building issues. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
4/9/2009
LEED Interpretation
Inquiry:
The project is an office building with a sloped standing seam metal roof. The rise is approximately 6\'-4" over 36\'-6" for a slope of 2.08:12. The design team requests verification that any slope exceeding exactly 2:12 is allowed an SRI value of 29 for the roofing material.
Ruling:
The project team is requesting clarification as to whether a roof slope that only slightly exceeds 2:12 can meet this credit by having roofing material with a minimum SRI value of 29. As indicated in the credit requirements, if the slope of the roof is greater than 2:12 (even if only slightly), the SRI requirement is 29. Please provide the necessary supporting documentation (plans, calculations, etc.) to support the claim. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
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Intent
To reduce heat islands1 to minimize impacts on microclimates and human and wildlife habitats.
Requirements
Option 1
Use roofing materials with a solar reflectance index (SRI)2 equal to or greater than the values in the table below for a minimum of 75% of the roof surface. Roofing materials having a lower SIR value than those listed below ay be used if the weighted rooftop SRI average meets the following:|
Area Roof Meeting Minimum SRI ———————————————— Total Roof Area |
x |
SRI of Installed Roof —————————— Required SRI |
≥ |
75% |
OR
Option 2
Install and maintain a vegetated roof that covers at least 50% of the roof area.OR
Option 3
Install high-albedo and vegetated roof surfaces that, in combination, meet the following criteria:|
Area Roof Meeting Minimum SRI ———————————————— 0.75 |
+ |
Area of Vegetated Roof —————————— 0.5 |
≥ |
Total Roof Area |
|
Roof Type |
Slope |
|
|
Low-sloped roof |
≤ 2:12 |
78 |
|
Steep-sloped roof |
> 2:12 |
29 |
1 Heat islands are defined as thermal gradient differences between developed and underdeveloped areas.
2 The solar reflectance index (SRI) is a measure of the constructed surface's ability to reflect solar heat, as shown by a small temperature rise. It is defined so that a standardblack surface (reflectance 0.05, emittance 0.90) is 0 and a standard white surface (reflectance 0.80, emittance 0.90) is 100. to calculate the SRI for a given material, obtain the reflectance value and emittance value for the material. SRI is calculated according to ASTM E 1980. Reflectance is measured according to ASTM E 903, ASTM E 1918, or ASTM C 1549. Emittance is measured according to ASTM E408 or ASTM C 1371.
3 For the purposes of this credit, under cover parking is defined as parking underground, under deck, under roof, or under a building.
Credit substitution available
You may use the LEED v4 version of this credit on v2009 projects. For more information check out this article.XX%
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8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Add "skylights" to the list of things deducted from the roof area so that the sentence reads, "Determine the area of the roof covered by mechanical equipment, solar energy panels, skylights, and other appurtenances, and deduct these areas from the total roof surface area."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Below equation, add the text and equation:Alternatively, the following equation may be used to calculate compliance:(see image)
Campus Applicable
No
Internationally Applicable:
No
10/1/2012 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In the second sentence, delete "Particularly in urban areas"; revise the last clause so that it reads, "Other sources may include vehicle exhaust, air-conditioners, and street equipment. Reduced airflow because of tall buildings and narrow streets exacerbate the effect."
Campus Applicable
No
Internationally Applicable:
No
7/6/2012 – Updated: 2/14/2015
Global ACP
Description of change:
Delete the Note for Projects Outside the U.S.
Campus Applicable
No
Internationally Applicable:
Yes
8/1/2011 – Updated: 2/14/2015
Rating System Correction
Description of change:
Below equation, add the text and equation:Alternatively, the following equation may be used to calculate compliance:(see image)
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Replace the term "photovoltaic panels" with "solar energy panels" and add "other appurtenances" to the list of things deducted from the roof area so that the sentence reads "Projects may earn an Innovation in Operations (IO) credit for exemplary performance by demonstrating that 95% of the project\'s roof area (excluding any mechanical equipment, solar energy panels, skylights, and other appurtenances) consists of a vegetated roof system."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In alphabetical order, add the term, "Roof area is the area of the uppermost surface of the building which covers enclosed Gross Floor Area, as measured when projected onto a flat, horizontal surface (i.e. as seen in Roof Plan view). \'Roofs\', or portions of roofs, covering unenclosed areas (e.g. roofs over porches and open covered parking structures) are not included in the areas used to evaluate compliance with SSc7.2, though they may be applicable to SSc7.1."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Below equation, add the text and equation:Alternatively, a weighted average approach may be used to calculate compliance for multiple materials:(see image)
Campus Applicable
No
Internationally Applicable:
No
10/1/2012 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
Replace the definition of "solar reflectance (SR)" with "the fraction of solar energy that is reflected by a surface on a scale of 0 to 1. Black paint has a solar reflectance of 0; white paint (titanium dioxide) has a solar reflectance of 1. The standard technique for its determination uses spectrophotometric measurements, with an integrating sphere to determine the reflectance at each wavelength. The average reflectance is then determined by an averaging process, using a standard solar spectrum, as documented by ASTM Standards E903 and E892."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Reference Guide Correction
Description of change:
In alphabetical order, add the term "An appurtenance is any built-in, nonstructural portion of a roof system, such as skylights, ventilators, mechanical equipment, partitions, and solar energy panels."
Campus Applicable
No
Internationally Applicable:
No
8/1/2011 – Updated: 2/14/2015
Rating System Correction
Description of change:
Below equation, add the text and equation:Alternatively, a weighted average approach may be used to calculate compliance for multiple materials:(see image)
Campus Applicable
No
Internationally Applicable:
No
6/19/2008
LEED Interpretation
Inquiry:
Our project uses three different roof systems that contribute to minimizing the heat island effect. Due to the complexity of the roof on this project, calculation of LEED NCv2.2 Credit 7.2 is not entirely clear, as the reference guide offers two formulas for addressing multiple roofing types. Additionally, the building is under an historic preservation easement in the City of Pittsburgh that requires that the pitched roof portion of the building that is visible to the street and passersby be either restored to its original construction, dark slate, or to its most recent construction, asphalt shingles. The first roof system is a vegetative roof that comprises 1,424 sq ft of roof area. The second roof system is a flat roof with a PVC membrane with an SRI of 104 and covers 1,250sqft. The third roof is a steep sloped roof that for the historical reasons above has a faux slate product with an SRI of 8 and covers 1,680sqft. The total roof is 4,354sf, of which 39% is comprised by the historic roof. Due to the number of roofing systems on this project and their differences, no single equation from the LEED NCv2.2 Reference Guide will allow us to appropriately determine the net effect the total roof has on the urban heat island effect. By combining two of the compliance paths already determined by the LEED NCv2.2 reference guide it may be possible to determine one compliance path to cover one project regardless of the complexity of the roof. The reference guide gives four possible compliance paths: Option 1: 75% of the roof surface is required to meet the minimum SRI value for a particular roof type (Area of SRI roof/0.75)>=Total Roof Area Option 2: Vegetative roof is at least 50% of the total roof area (Area of Vegetated Roof/0.5)>= Total Roof Area Option 3: Combine Option 1 and 2 (Area of SRI roof/.75)+(Area of Vegetated Roof/0.5)>=Total Roof Area Option 4: Referenced in the Calculations Section, Weighted averaging to show that the total theoretical roof does comply (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...>=Total Roof Area To show that the proposed roof of this project does comply with the intent of this credit, the two equations needed would be from \'Option 2\' and \'Option 4\'. The precedent for combining these two calculations comes from \'Option 3\'. Our interpretation on combining different compliance paths is that they can be added together as long as the areas in each equation are independent of one another so that any area on the roof cannot be counted more than once. We propose the following equation for a roof consisting of a vegetative roof along with two or more other roofing systems: (Area of Roof A)*(SRI of Roof A/Required SRI)+(Area of Roof B)*(SRI of Roof B/Required SRI)+...+(Area of Vegetated Roof/0.5)>=Total Roof Area For this and other projects using multiple roof constructions, does the above calculation meet the intent of the credit, and will this be considered an additional path of compliance? Also, is it possible to exclude historic roofs from SS7.2 calculations?
Ruling:
The CIR is requesting clarification on the appropriate formula to use when calculating SSc7.2 compliance for multiple roof materials in addition to vegetated roof area. The project is also requesting permission to exclude roof areas which are subject to historical preservation requirements from the credit calculations. The project may use the following formula to calculate credit compliance for multiple materials including vegetated roof areas: [(Area of Roof A*(SRI of Roof A/Required SRI)) + (Area of Roof B*(SRI of Roof B/Required SRI)) / 0.75] + [ Area of Vegetated Roof/0.5] >= Total Roof Area Historical Roof Areas may not be excluded from the calculations. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
11/1/2011
LEED Interpretation
Inquiry:
There is a stainless steel tube veil that covers the complete building. The tubes are placed with a 1 mm spacing between each other, and the material interior cannot be seen. Therefore, we would like to conduct a test to verify if the SRI of the tubes will comply with the LEED requirements (equal or greater than 78). Due to the originality of the exterior facade, we would like to know what type of test should be conducted:
Option 1 - Test using a 4mx4m mock up of the roof assembly and test the reflectance per ASTM 1918,
Option 2 - A flat sample test of all the materials installed on the roof
Please advise if there are any other tests that would need to be conducted.
Ruling:
The Referenced LEED Standard of ASTM 1918-97 has been superseded by ASTM 1918-06. For a roof with a veil design, or similar non-homogenous materials, the project should perform a SRI test to ASTM E1175 - 87(2009) Standard Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere. When submitting for LEED Certification, please include a copy of this interpretation and a summary of any testing results that document the SRI rating for the installed veil surface.Projects may wish to test any mock-up to assess credit compliance before testing installed materials, but the testing for certification should be done for the installed roofing assembly. Applicable internationally.
Campus Applicable
No
Internationally Applicable:
Yes
9/5/2008
LEED Interpretation
Inquiry:
In an effort to reduce heat islands, the car park for this hotel project is covered. All of the building car park is at ground level (there is no basement). The car park cover is made up of both the hotel building and a podium area that extends out from the hotel. The roof area includes: Podium Roof: 1. Green roof area - 394m2 2. Hardscaped area - 832m2 (The hardscaped area is in two parts. An area on one side of the building for pedestrian use and an area at the rear of the building which contains a vehicular ramp where cars will drive over the corner of the site) 3. Total podium roof area (1+2) = 1226m2 Building Roof: 4. Total footprint (including stairs & plant) - 1084m2 5. Total footprint (excluding stairs & plant) - 836m2 Can the podium roof (including the green roof) be included in the total roof surface for this project?
Ruling:
The podium deck, which covers on-grade parking, cannot be considered a roof area for the purposes of this credit. CIR Ruling dated 9/24/2001 rules that the top deck of an above-grade parking structure is to be considered non-roof impervious area. If the podium deck covered conditioned space, then the deck could be considered as a roof (for portions not being used for parking). Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/1/2012
LEED Interpretation
Inquiry:
Can helipads and other functional space areas be exempted from SSc7.2 Heat Island Effect- Roof calculations?
Ruling:
Roof area that consists of functional, usable spaces- such as helipads, recreation courts, and areas covered by equipment, solar panels, and appurtenances- can be exempted from the roof calculations for SSc7.2. Projects are not eligible for SSc7.2 if the exempted spaces encompass the entire roof area. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
9/20/2004
LEED Interpretation
Inquiry:
Our building has a flat roof membrane which is specified to comply with all requirements of this Credit. However, as part of our approval process the County also required, purely for aesthetics, a free-standing curved roof canopy which stands over some mechanical equipment but which mainly stands over and actually shades much (~40%) of the actual roof membrane. This curved roof canopy system does not directly connect to the building envelope except at its column bases and has a free flow of air between it and the roof membrane. As such, our question is whether this freestanding curved roof canopy material (which is currently specified as painted metal, but which may also be a membrane material) must be counted in the 75% of available roof area required by this Credit to achieve both Energy Star reflectance criteria (which it actually does) and emissivity (for which it has not been tested using ASTM E408).
Ruling:
The canopy is effectively part of the roofing system as it relates to reflectivity and should be included in calculations for this credit. Please refer to SSc7.2 CIR ruling dated 3/11/2003 for further guidance. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
1/23/2006
LEED Interpretation
Inquiry:
Previous CIRs have allowed the use of a weighted average approach for the reflectance and for the emissivity of a roof material. A baseline reflectance is calculated by applying the minimum reflectance of the roof (0.65) and multiplying it by the percentage of roof it covers (75%). This calculation results in a baseline reflectance of 0.4875. Similarly, baseline emissivity can be calculated as 0.90 x 75% = 0.675. Can this weighted average approach be used for both of these values simultaneously? In other words, if a roof material covers 100% of the roof area, and its reflectance is 0.4875 or greater, and its emissivity is 0.675 or greater, does it meet the credit requirements? Will the weighted average approach also be allowed as it pertains to a roof\'s SRI under v2.2?
Ruling:
Per the CIR Ruling for SSc7.1 dated 12/05/01, you may perform a weighted average calculation for the reflectivity. Alternatively, you may apply the weighted average for emissivity instead of reflectivity, but not both (it would be too lenient compared to the original credit requirements). The weighted average approach can be used for SRI in NC v2.2. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/11/2007
LEED Interpretation
Inquiry:
Our project contains low slope roof, steep slope roof, and vegetative roof conditions. All specified roof products meet requirement for EMITTANCE of .90 or greater based on ASTM E408-71. Project will need to perform a "Weighted Average" to attain required SOLAR REFLECTANCE. Due to steep slope roofs, low slope roofs, and vegetative roofs having different requirements for reflectance I am assuming when considering the weighted average base on "CIR SS7.1 12/5/2001" these three are to be considered separately. We have specified adhered membrane roof (energy smart light grey) (solar reflectance = .49) in both steep slope and low slope conditions, vegetative roof area (low slope), and recycled synthetic shake shingle (steep slope) (solar reflectance = .18). Low Slope Roof Required (6%): (75% x .65) = .4875 Actual Low Slope (adhered membrane) (100%): .49 Steep Slope Roof Required (59%):(75% x .25) = .1875 Actual Steep Slope (Recycled Shake Shingle 75%): .18 Actual Steep Slope (adhered membrane 25%): .49 Actual Average: .75(.18) + .25(.49) = .25 Vegetative Roof (35%) We also need clarification of interpretation of Solar Reflectance Value determined for the specified Recycled Shingle. Specified product is designed to lighten up and grey as part of its natural weathering process. Product pulled off of production line does not meet required values for reflectance. However, ASTM E903 tests performed after just 6 months of weathering indicated an average tested solar reflectance of .18. This value falls with-in the allowed weighted average to attain the point. This product also tested at .15 after three years which also passes Energy Star guidelines with out considering weighted average. We feel that using the 6 month weathered values for solar reflectance should be considered in this case due to the fact that our specified product attains required value after only 1% of its warrentied life (considering it has a 50 year unconditional transferable warranty and a 100 year life expectancy). Please comment as to whether the above assumptions are consistent with your intent for credit SS7.2 Reduce Heat Island (Roof) and will or will not attain credit. Thank you.
Ruling:
The methodology noted in SSc7.1 CIR Ruling dated 12/5/2001 is appropriate to demonstrate compliance with SSc7.2. The "weighted average" methodology when applied to the roofing materials used on low slope and steep slope conditions can provide teams with an alternative method for achieving this credit. It appears from the values above that this project would meet the credit requirements set forth and referenced in the EPA Energy Star Roofing Guidelines. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/17/2007
LEED Interpretation
Inquiry:
Since SSc7.2 roof area calculations exclude skylights, parapets, equipment, paving, and other rooftop surfaces ineligible for EnergyStar consideration, we question whether the translucent tensile fabric structure covering portions of our Project qualifies as "roof" in SSc7.2 calculations. For our Project, the proposed fabric roof covers unconditioned outdoor space, but the same questions may apply on projects using similar products to enclose conditioned interiors. The manufacturer of the proposed tensile fabric system claims that their membrane meets EnergyStar reflectivity requirements and that they are pursuing California Cool Roof and EnergyStar ratings. On this basis, we included this area in our initial roof area calculations. However, the manufacturer has not submitted conclusive evidence supporting their claim. We received ASTM E408 test reports confirming their product\'s emissivity, but submittals have referenced ASTM E424 reflectivity tests, not the ASTM E903 & C1549 tests cited in EnergyStar\'s Eligibility Criteria. The manufacturer asserts that ASTM E424 test for visible light reflectivity is equivalent to E903. They have only submitted data for new materials, but they have not complied with EnergyStar\'s aged testing requirements. SSc7.2 Credit Requirements specifically refer to EnergyStar Eligibility Criteria and ASTM E903 tests for solar reflectance, noting that visible reflectance is irrelevant to Credit compliance. Past CIRs emphasize the requirement for aged testing and the need for all testing to conform to the specific, cited ASTM methods. However, these tests may be inapplicable to translucent materials, and such materials may not even qualify as "roofs" under EnergyStar Eligibility Criteria. EnergyStar\'s Eligibility Criteria define "roof surface" as, "The uppermost part of the roof system that is in direct contact with solar radiation", yet their list of "Qualifying Products" does not include light-transmitting roof materials such as glass, plastic, fiberglass, or fabric. All roof types defined in the Criteria appear to be opaque membranes, coatings, tiles, and shingles applied directly to structure. Both cited reflectivity tests, ASTM E903 and C1549, apply primarily to opaque membranes, referring to other test methods for translucent materials. [Measurements of reflectivity and emissivity alone may not accurately gauge heat-island effect at clear or translucent materials. Opaque roofs can only reflect solar radiation or convert it to heat. When considering translucent materials, one may need to deduct energy from transmitted light as well.] If the tensile structure counts toward our total Project roof area, but fails to achieve EnergyStar, one of the buildings on our campus will not meet the 75% EnergyStar/high-emissivity requirement. [All other buildings do comply, including the Main Building, whose EnergyStar roof makes up at least 87% of the total Project roof area. However, the Main Building\'s designer can only sign the Letter Template for his own scope. We had hoped that each building could comply independently, allowing each designer to sign SSc7.2 Letter Templates for each respective scope.] If we can exclude the tensile roof from the total Project roof area, all buildings will clearly comply. Can we omit light-transmitting materials, such as those described above, from SSc7.2 roof area calculations as we would skylights? If not, what tests, applicable to light-transmitting materials, will demonstrate EnergyStar equivalence of such materials? Finally, if one of our three Designer\'s scopes cannot demonstrate Credit compliance, can the Project still achieve the Credit based on Letter Templates from the remaining Designers?
Ruling:
While Energy Star defines a roof surface as "the uppermost part of the roof system that is in direct contact with solar radiation," based on the description of the tensile fabric canopy system, it does not appear that the system meets the definition of a roof. The credit\'s testing standards (Energy Star\'s Program for Roof Products) focus on systems and/or products that are considered permanent, primary systems whose sole function is to shelter the elements, e.g. rain, snow, wind, etc. from entering the building. The project team describes their fabric system as covering unconditioned outdoor space, not a building. Thus, it is acting as a shade structure. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/27/2009
LEED Interpretation
Inquiry:
Our project comprises a commercial office tower with an associated podium for carparking. As part of the architectural design, a non-load bearing laminated glass canopy will be constructed from the main office tower and extend over the ground floor public plaza. The canopy will also partly cover the podium. The top deck of the podium will be carparking, and therefore the canopy will in park cover this carparking. Please can you confirm whether this glass canopy should be considered as a \'roof\' under SS-C7.2, and as a glass structure whether it should be exempt from SRI calculations?
Ruling:
Yes, the glass canopy can be excluded from SRI roof requirements under SSc7.2 as it covers an unconditioned outdoor space, not a building. Per NCv2.2 SSc7.1 CIR ruling dated 2/14/2008, the glass canopy can be excluded from SRI requirements under SSc7.1 if parking is placed underground or under deck, so long as the exposed parking area is less than or equal to 50 percent of the total parking surface. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
8/1/2011
LEED Interpretation
Inquiry:
Many of the ASTM Standards we reference have been withdrawn, upgraded, or superseded. Provide guidance on which updated standards should be used.
Ruling:
The withdrawn ASTM Standards listed- ASTM E1980-01 and ASTM E903-96- are still the correct references for SSc1: Site Selection, SSc7.1: Heat Island Effect, Non-Roof, and SSc7.2: Heat Island Effect-Roof. These two standards were not withdrawn for technical reasons, but were withdrawn because they had not been updated within 8 years. Testing can still be performed for these as well as the superseded standards. The updated versions of the superseded standards can be used, but are not required:Old: ASTM E408-71(1996), Current: E408-71(2008)Old: ASTM C1371-04a, Current: C1371-04a(2010)Old: ASTM E1918-97, Current: E1918-06 Old: ASTM C1549-04, Current: 1549-09Note: This Interpretations is also applicable to Sustainable Sites Credit 7.1: Heat Island Effect- Non-Roof and Sustainable Sites Credit 1: Site Selection, see LEED Interpretations dated 8/1/2011 ID number 10092 and 10094 respectively. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/2/2008
LEED Interpretation
Inquiry:
Many CIRs address the fact that you can use the weighted average method outlined in the SSc7.1 CIR dated 12/5/2001 for SSc7.2. That CIR outlined a baseline which assumed 30% of the site met the 0.3 reflectance requirement, and 70% did not. However, the NCv2.2 Reference Guide for SSc7.2 outlines a weighted average calculation which differs from the SSc7.1 method in two ways. The first is that the outlined baseline (75% w/ SRI of 78 & 25% w/ SRI of 30) requires that 100% of the roof area is compliant with the SRI requirements. Also, the outlined baseline assumes that 75% of the roof area is low sloped, and 25% is steep sloped. If a project has a low slope for 64% and a steep slope for 36% of the roof area, can we use a baseline weighted average which reflects our ratio of steep to low sloped roof? Also, can we use a baseline weighted average calculation which requires 75% of the roof area to be compliant instead of 100% of the roof area? I\'ve outlined an example below: If 75% of the low sloped roof is compliant, for our project this would mean 48% (64%x0.75) of the total roof area should have an SRI of at least 78. If 75% of the steep sloped roof is compliant, this would mean 27% (36%x0.75) of the total roof area should have an SRI of at least 29. Since 48% + 27% = 75% of the total roof area, this method reflects credit requirements and is consistent with the weighted average methodology outlined in the SSc7.1 CIR. Therefore, the weighted average baseline would be: 27% x 29 + 48% x 78 = 45.27 Can this calculation methodology be used to calculate the baseline for the weighted average option for SSc7.2?
Ruling:
Can a project use a weighted average calculation to show credit compliance? Yes, projects may use a weighted average calculation to achieve compliance equivalent to the required 75% threshold. As noted in v2.2 SSc7.2 CIR Ruling dated 6/19/2008, if the project applies for this credit under v2.2, the project may use the following formula to calculate credit compliance for multiple materials: [(Area of Roof A*(SRI of Roof A/Required SRI)) + (Area of Roof B*(SRI of Roof B/Required SRI)) / 0.75] + [ Area of Vegetated Roof/0.5] >= Total Roof Area In order for a project registered for v2.1 to apply for this credit using the v2.2 requirements, the project team must submit through LEED Online and follow the process outlined in the Credit Substitution Memo dated 12/19/2006 which can be found on the USGBC\'s website at: www.usgbc.org/ShowFile.aspx?DocumentID=1704 Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
10/1/2012
LEED Interpretation
Inquiry:
Can sidewalks, roads, and other hardscape areas located above a project building\'s underground parking structure, which are required by the governing municipality to be constructed of non-compliant materials, be excluded from the SSc7.2 and SSc7.1 calculations?
Ruling:
Similar to LEED Interpretations #2293 and #3101, sidewalks, roads, and areas that cover un-conditioned spaces (such as parking garages) are considered hardscape or landscape nonroof surfaces. Thus, they should be included in the calculations for SSc7.1 Heat Island Effect- Nonroof. In situations where infrastructure, materials, or surfaces are owned, operated and maintained by the local governing body, project teams may exclude the area of the material from the calculations for SSc7.2 and SSc7.1. This exemption can be applied only if projects do not have any control over the materials used for the surfaces in question. If the materials are owned and operated by the project, but the local jurisdiction specifies that they must meet certain criteria, the materials may not be excluded from the calculations. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
1/29/2009
LEED Interpretation
Inquiry:
The project is a multiple building (campus) submission, it is for 2 1/2 million square feet of office, amenity and associated support functions. The flat roofing type selected by the team for the majority of roof area is a Protected Roof Membrane assembly, which consists of a roofing membrane on the roof slab, covered by rigid insulation, which is then covered by medium weight (17-20 PSF) gravel ballast. The design and construction team was unable to find "white coated gravel" listed in the reference guide for light colored ballast that complies with SRI requirements for the point. The Oak Ridge National Laboratories published a four-year study of ballasted roofing assemblies that indicated that medium weight ballasted roofing systems performed as well or better than white roof systems for reducing the heat of the roofing membrane, and recommended that these systems be considered "cool roof" systems as well. The study also noted that these values were constant over a four year period, while the temperature reduction values for the white membrane roof degraded within the first year to a much lower value. We are aware that the study focused on the thermal performance of the system specifically related to heat transfer through the ballast to the membrane, but since the study showed that approximately the same (or less) heat got to the membrane than on a white (SRI compliant) roof at peak, we conclude that the rest of the heat is being rejected back into the air similar to the performance of the white roof. We spoke to the primary investigator on the study, Andre Desjarlais from ORNL, and he said the following: "What the ballast does is redistribute the temperature profile. Unlike a cool roof that simply reflects the solar load away, ballast stores the load and distributes it differently over the daily cycle." By using ballast, we are meeting the peak temperatures of the credit, although it is likely that we will end up with slightly higher temperatures emitting from the roof later in the day. The design team believes that this system, with its ability to dampen the temperature swings associated with a dark-colored roof, meets the intent of the LEED Credit. Can we consider this roofing system to meet the intent of the SS Credit 7.2 as an alternative method through performance? The study is called "Evaluating the Energy Performance of Ballasted Roof Systems" and was published in April, 2008. It is available at http://www.spri.org under "Technical Reports."
Ruling:
The CIR requests confirmation that a flat roofing type selected for the majority of roof area meets the intent of SS Credit 7.2 as an alternative method through performance. While the attributes of a flat roofing system using medium-weight ballast is shown by the ORNL study to have similar performance results for reducing cooling loads as a white cool roof system, that claim alone does not allow for an alternative compliance path for this credit. The intent of this credit relates to the microclimate of the surrounding area and its impact on local habitat. Cooling load comparisons only address the mechanical efficiency of the interior space of the project building. The ORNL study did not show an SRI of at least 78 for the ballast materials under study, which is required for this credit. Accordingly, this roofing system does not meet the intent of SS c7.2. The benefit of using a medium-weight ballast roof system might more appropriately be found in helping to achieve additional points toward EA Credit 1 - Optimize Energy Performance. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
12/5/2005
LEED Interpretation
Inquiry:
Our residential project is comprised of two multi-story towers that are connected on the ground floor with a single-story atrium that is sandwiched between the two towers. The sum of the two tower roofs equals 17,586 s.f. and makes up 70% of the total roof area. In order to comply with this credit and reduce heat islands, the two tower roofs are specified as a white TPO membrane that meets the emissivity and Energy Star requirements. We could easily achieve the credit requirement of 75% of the roof area by specifying white membrane for 1,254 s.f. of the 7,484 s.f. lower roof. However, in this case, we feel that having a high albedo lower roof would actually conflict with the intent of the credit. 97% of the curtain wall is glass, thus the towers would be subject to heat gain because the solar reflectance would project back up into the buildings. In addition, all of the residential units that face the atrium will have direct views of the roof which would expose the residents to glare. We propose to install a gray TPO membrane on the lower roof. This would not produce glare or contribute to as much heat gain as the white membrane, but still have a higher emissivity level than a standard black membrane. Given the circumstances, would you award us credit if the upper roofs are white and the lower roof is gray?
Ruling:
Per the CIR Ruling for SSc7.1 dated 12/05/01, you may perform a weighted average calculation for the reflectivity. Alternatively, you may apply the weighted average for emissivity instead of reflectivity (but allowing both would be too lenient). For example, the reflectance minimum weighted average can be calculated by applying the minimum reflectance of the roof (.65) and multiplying it by the percentage of roof coverage required (75% min.). This calculation results yields a baseline reflectivity average of 0.4875. For this example, each surface must comply with the emissivity requirement independently. If the average reflectance for your total roof area are above the minimum weighted averages, the overall criteria would be satisfied. NOTE: depending on the building orientation, reflection off the curtain walls could result in significant heat gain to the single story atrium. You might consider integrating a green roof over the single story atrium which would provide a pleasant view for the residents, eliminate the glare issue, and meet the intent of the credit.
Campus Applicable
No
Internationally Applicable:
No
9/24/2001
LEED Interpretation
Inquiry:
The parking for this project is a parking structure adjacent to the office building which is approximately equal in area to the "roof area" of the building. Is the upper deck of the parking structure to be a "roof" and therefore to be included in the total quantity of roof surface for this project? If so, is it necessary that an Energy Star high-reflectance and high emissivity coating be applied to the upper deck of the parking structure?
Ruling:
The upper deck of a parking garage is considered a non-roof impervious surface. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
7/11/2007
LEED Interpretation
Inquiry:
The project is a 43 acre urban development with 8 primary buildings containing roughly 17,000,000 s.f. of space. The LEED documentation for this project will be submitted concurrently as 8 separate submittals, one for each building; however, certain SS and WE credits will be submitted as campus credits as they pertain to the project at large. We are requesting approval to submit SSc7.2 as a campus credit since the SRI requirements have been calculated, and exceeded on a project-wide level. The weighted average roof calculation method described on page 98 of the LEED v2.2 Reference Guide was used to calculate a total weighted SRI of 84 for the project, which exceeds the theoretical SRI of 66 (75% of roof area = SRI 78 and 25% of roof area = SRI 30). In fact, 82% of the total campus roof area has an SRI that exceeds the theoretical SRI value of 66. The following weighted average calculation approach was used to determine the project-wide weighted SRI for all roofing surfaces: (Area of Roof Surface A / Total Campus Roof Area) * SRI of Roof Surface A) + (Area of Roof Surface B / Total Campus Roof Area) * SRI of Roof Surface B) + (Area of Roof Surface C / Total Campus Roof Area) * SRI of Roof Surface C) = Total project-wide weighted SRI Similar to other campus credits, the heat island effect is of campus-wide concern since the ambient air temperature around and above the development is directly affected by the albedo of selected roofing surfaces. By exceeding the SRI requirements for this credit on a campus-wide level, the heat island effect and associated cooling energy loads have been minimized, therefore promoting a healthier environment for the humans and wildlife that inhabit this development. We request confirmation that the proposed strategy to submit SSc7.2 as a campus credit is acceptable to achieve the intent of this credit.
Ruling:
The applicant is seeking to submit this credit based on a campus-wide aggregate of all the roof surfaces and corresponding SRI values. However, based on the LEED-NC Application Guide for Multiple Buildings & On-Campus Projects (AGMBC), which deals with campus situations like this, this approach is not acceptable for LEED projects to demonstrate individual achievement through weighted averaging of achievement across multiple LEED projects. The AGMBC does allow multiple buildings to submit as a single LEED project, for which the weighted average approach described above would be appropriate.Update April 15, 2011: Please note that all 2009 projects in multiple building situations must follow the 2010 Application Guide for Multiple Buildings and On-Campus Building Projects, located here: https://www.usgbc.org/ShowFile.aspx?DocumentID=7987. 2009 project teams should check this document for up to date guidance on all multiple building issues. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
4/9/2009
LEED Interpretation
Inquiry:
The project is an office building with a sloped standing seam metal roof. The rise is approximately 6\'-4" over 36\'-6" for a slope of 2.08:12. The design team requests verification that any slope exceeding exactly 2:12 is allowed an SRI value of 29 for the roofing material.
Ruling:
The project team is requesting clarification as to whether a roof slope that only slightly exceeds 2:12 can meet this credit by having roofing material with a minimum SRI value of 29. As indicated in the credit requirements, if the slope of the roof is greater than 2:12 (even if only slightly), the SRI requirement is 29. Please provide the necessary supporting documentation (plans, calculations, etc.) to support the claim. Applicable Internationally.
Campus Applicable
No
Internationally Applicable:
Yes
LEEDuser expert
Ashwini Arun
WSP
Senior Sustainability Manager
