Retail-NC-v4 SSc5: Heat island reduction

  • A menu of heat island reduction options

    This credit offers several different compliance paths to choose from, making it a very achievable credit for most projects. It’s common for teams to pursue the reflective materials option for roof and/or hardscapeThe inanimate elements of the building landscaping. It includes pavement, roadways, stonewalls, wood and synthetic decking, concrete paths and sidewalks, and concrete, brick, and tile patios.. Providing parking undercover is another popular option that’s highly achievable for projects that include a parking garage.

    Teams also have the option to retain existing shade trees and plant new trees to shade paved areas onsite. Vegetated roofs contribute to this credit as well.

    What’s New in LEED v4

    • This credit combines the roof and nonroof heat island credits contained in LEED 2009.
    • USGBC now determines credit compliance for nonroof hardscape using SR values instead of SRIA measure of the constructed surface's ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation. It is defined such that a standard black surface (initial solar reflectance 0.05, initial thermal emittance 0.90) has an initial SRI of 0, and a standard white surface (initial solar reflectance 0.80, initial thermal emittance 0.90) has an initial SRI of 100. To calculate the SRI for a given material, obtain its solar reflectance and thermal emittance via the Cool Roof Rating Council Standard (CRRC-1). SRI is calculated according to ASTM E 1980. Calculation of the aged SRI is based on the aged tested values of solar reflectance and thermal emittance. values.
    • High-reflectance and vegetated roof surfaces now have equal weight in performance calculations.
    • USGBC now calculates the shade area from tree canopy after 10 years of landscape installation rather than five years.
    • LEED increased the initial SRI thresholds for roofing material.
    • LEED now factors in the three-year aged SRI values for roofing material for this credit.

    FAQs 

    If the manufacturer cannot provide the SR or SRI values, can standard values be used based on the color of the material?

    Teams must provide manufacturer documentation or independent testing demonstrating SRI value for roofing material and SR value for nonroof material.

    Typical SR values for gray cement concrete, white cement concrete and asphalt concrete can be used for standard nonroof materials per LEED Interpretation #10411.

    Cool Roof Rating Council (CRRC) has a searchable product database.

    If independent testing is required, page 6 of the Cool Roof Rating Council Standard (CRRC-1) (PDF download) outlines the test methodology and number of tests required for different nonroof materials.

    If the top floor of a parking garage includes parking spaces, is it considered a roof or non-roof surface?

    If the top level of your parking structure has parking spaces, it is considered a nonroof surface, and needs to be included in the calculations for Option 1 under “Area of nonroof measures.”

    In LEED v4, are there standard allowed SRI values for things like concrete, as in LEED 2009?

    No. USGBC intentionally did not publish standard SRI values for LEED v4. According to USGBC, they found that the values for LEED 2009 were not appropriate for all materials (they were over-generalized), and they actually changed over the years in a couple instances as technologies improved, so they wound up being outdated. Projects should get information from other sources.

  • SS Credit 5: Heat island reduction

    Intent

    To minimize effects on microclimates and human and wildlife habitats by reducing heat islands.

    Requirements

    Choose one of the following options:

    Option 1. nonroof and roof (2 points except Healthcare, 1 point Healthcare)

    Meet the following criterion:

    Area of Nonroof Measures   Area of High-Reflectance Roof   Area of Vegetated Roof   Total Site Paving Area   Total Roof AreaRoof 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.
    —————— + —————— + —————— +
    0.5   0.75   0.75    



    Alternatively, an SRIA measure of the constructed surface's ability to stay cool in the sun by reflecting solar radiation and emitting thermal radiation. It is defined such that a standard black surface (initial solar reflectance 0.05, initial thermal emittance 0.90) has an initial SRI of 0, and a standard white surface (initial solar reflectance 0.80, initial thermal emittance 0.90) has an initial SRI of 100. To calculate the SRI for a given material, obtain its solar reflectance and thermal emittance via the Cool Roof Rating Council Standard (CRRC-1). SRI is calculated according to ASTM E 1980. Calculation of the aged SRI is based on the aged tested values of solar reflectance and thermal emittance. and SR weighted average approach may be used to calculate compliance.

    Use any combination of the following strategies.

    Nonroof measures

    • Use the existing plant material or install plants that provide shade over paving areas (including playgrounds) on the site within 10 years of planting. Install vegetated planters. Plants must be in place at the time of occupancy permit and cannot include artificial turf.
    • Provide shade with structures covered by energy generation systems, such as solar thermal collectors, photovoltaics, and wind turbines.
    • Provide shade with architectural devices or structures that have a three-year aged solar reflectanceAlso known as albedo: 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 (SR) value of at least 0.28. If three-year aged value information is not available, use materials with an initial SR of at least 0.33 at installation.
    • Provide shade with vegetated structures.
    • Use paving materials with a three-year aged solar reflectance (SR) value of at least 0.28. If three-year aged value information is not available, use materials with an initial SR of at least 0.33 at installation.
    • Use an open-grid pavement system Pavements that consist of loose substrates supported by a grid of a more structurally sound grid or webbing. Pervious concrete and porous asphalt are not considered open grid as they are considered bounded materials. Unbounded, loose substrates do not transfer and store heat like bound and compacted materials do.(at least 50% unbound).

    High-reflectance roof

    Use roofing materials that have an SRI equal to or greater than the values in Table 1. Meet the three-year aged SRI value. If three-year aged value information is not available, use materials that meet the initial SRI value.

    Table 1. Minimum solar reflectance index value, by roof slope

      Slope Initial SRI OR 3-year aged SRI
    Low-sloped roof ≤ 2:12 82   64
    Steep-sloped roof > 2:12 39   32



    Vegetated roof

    Install a vegetated roof.

    OR

    Option 2. parking under cover (1 point)

    Place a minimum of 75% of parking spaces under cover. Any roof used to shade or cover parking must (1) have a three-year aged SRI of at least 32 (if three-year aged value information is not available, use materials with an initial SRI of at least 39 at installation), (2) be a vegetated roof, or (3) be covered by energy generation systems, such as solar thermal collectors, photovoltaics, and wind turbines.

    SITES-LEED Equivalency

    This LEED credit (or a component of this credit) has been established as equivalent to a SITES v2 credit or component. For more information on using the equivalency as a substitution in your LEED or SITES project, see this article and guidance document.

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Mar 26 2017
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