C4.9: Reduce Urban Heat Island Effects

(4 points)

INTENT

Minimize effects on microclimate and human and wildlife habitat by using vegetation and reflective materials to reduce heat island effects.

REQUIREMENTS*

Use any combination of the following measures to reduce urban heat island effects for site paving and structures (including roads, sidewalks, courtyards, playgrounds, shelters, and parking lots) according to the formula below:

Alternatively, a solar reflectance index (SRI) and solar reflectance (SR) weighted average approach may be used to calculate compliance.

• Non-roof 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. Plants must be in place at the time of certification application.
  • Install vegetated planters. Plants must be in place at time of certification application and cannot contain artificial turf.
  • Provide shade with structures covered by energy generation systems that produce renewable energy such as solar thermal heaters, photovoltaics, and wind turbines.
  • Provide shade with architectural devices or structures that have an SR value at installation of at least 0.33 OR a three-year old SR of at least 0.28, and incorporate into the site maintenance plan (see O+M P8.1: Plan for sustainable site maintenance) activities to ensure these surfaces are cleaned at least every two years to maintain reflectivity.
  • Provide shade with vegetated structures.
  • Use paving materials with an SR of at least 0.33 at installation, OR a three-year aged SR value of at least 0.28, and incorporate into the site maintenance plan (see O+M P8.1: Plan for sustainable site maintenance) activities to ensure these surfaces are cleaned at least every two years to maintain reflectivity.
  • Use an open-grid pavement system (e.g., concrete-grass lattice) that is at least 50 percent unbound.

• High-reflectance roof
  • Use roofing materials that have an SRI equal to or greater than the values in the table below. Meet either the initial SR value, the three-year aged SR value, or both.

• Vegetated Roof
  • Install a vegetated roof.
    

Shade calculations must be based on the arithmetic mean of the percent wall and roof coverage at 10 a.m., noon, and 3 p.m. on the summer solstice.Vegetated RoofInstall a vegetated roof.

RECOMMENDED STRATEGIES

• Select strategies, materials, and landscaping techniques that reduce heat absorption by exterior surfaces.
• Reduce use of constructed impervious surfaces (e.g., roads, sidewalks, parking lots).
• Increase use of vegetated surfaces and planted areas.
• Use shade from appropriate trees, large shrubs, vegetated trellises, walls, or other exterior structures.
• Consider the use of new coatings and integral colorants for asphalt pavement to achieve light-colored surfaces instead of traditional dark surface materials.
• Position photovoltaic cells to shade impervious surfaces.
• Neither permeable concrete nor permeable asphalt meet the definition of open-grid paving system because both are more than 50 percent impervious. However, the SR of permeable concrete may be greater than 0.33.
• Consider placing parking under cover that complies with the above measures.

Consider placing parking under cover that complies with the above measures.

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