Pilot-Credits PC31: Heat Island Reduction

  • Heat island reduction measures combined in a single credit

    Note: This pilot credit was closed for new registrations as of March 1, 2012.

    Heat island effects in cities can increase summertime temperatures by 10 degrees or more, significantly increasing the cooling loads. LEED for Homes has always awarded credit for heat island reduction for both the roof and hardscapes. This is the first time that these two heat reduction measures (both under roof and hardscapes) are combined into a single credit.

    Additional Questions

    • What measures were installed to meet the requirements of the credit?
    • Do you feel that the thresholds are appropriate? If not, should they be lower or higher?

    Credit Submittals

    General

    1. Register for Pilot Credit(s) here.
    2. Register a username at LEEDuser.com, and participate in online forum
    3. Submit feedback survey; supply PDF of your survey/confirmation of completion with credit documentation

    Credit Specific

    Supporting Verification made available by the Project Team:

    • Provide calculation showing  that at least 50% of  hardscapes are either shaded or light colored/reflective
  • USGBC

    Excerpted from LEED 2009 for New Construction and Major Renovations

    Pilot Credit 31: Heat Island Reduction

    Intent

    To reduce heat islands such that impacts on microclimates, human and wildlife habitats are minimized.

    Requirements

    HOMES, MID-RISE


    Ensure that at least 50% of hardscapes (e.g., sidewalks, patios,
    driveways, parking lots and roofs) on the project site meet one of the
    following requirements:


    OPTION 1: Shading


    Locate trees or other plantings to provide shading of hardscapes. Shading should be cal-culated for noon on June 21, when the sun is directly overhead, based on five years’ growth.

    OR


    OPTION 2: Reflective Materials


    Install light-colored, high-albedoAlso known as solar reflectance: 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. materials or vegetation for hardscapes. Acceptable strategies include the following:

    • white concrete;
    • reflective roofing;
    • ENERGY STAR qualified roof products used in appropriately sloped application;
    • open pavers (counting only the vegetation, not the pavers), or an engineered grass paver; and
    • any material with a solar reflectance indexA 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. (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.) meeting the following criteria in Table 1.

    Table 1.

    Reflective materials having a lower SRI value than those listed above may be used if the weighted SRI average meets the following criteria:

Organizations

LEED Pilot Credit Library

The homepage for the LEED Pilot Credit Library. The LEED Pilot Credit Library is intended to facilitate the introduction of new prerequisites and credits to LEED. This process will allow USGBC to test and refine credits through LEED 2009 project evaluations before they are sent through the balloting process for introduction into LEED.

Articles

Foundations of LEED

Background for the LEED Pilot Credit Library is provided in this foundational document.

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Feb 26 2017
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