Page 98 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED Sustainable Sites 79

2.7 SS Credit Subcategory 7: Heat Island Effect

SS Credit 7.1: Heat Island Effect—Non-Roof
The urban heat island effect is a phenomenon where daily temperatures are higher in
urban areas than in the surrounding suburban and rural areas. It is thought to be caused
by many factors some of which are an increase in paved and roofed surfaces that collect
warmth from solar radiation, a decrease in foliage which can keep temperatures cooler by
evapotranspiration, and an increased energy use in buildings that also warms the ambient
air. This effect has many negative impacts including poorer air quality, an increase in
energy demand for cooling, an increase in water demand, a reduction in building material
durability, and an increase in human health concerns. Therefore, measures and construction
practices which reduce the urban heat island effect are encouraged.

USGBC Rating System
SSc7.1 is worth one point in LEED 2009 and was worth one point in LEED 2.2. LEED-
NC 2.2 lists the Intent, Requirements, and Potential Technologies and Strategies for this
credit as follows, with modifications as noted for LEED 2009:

Intent
Reduce heat islands (thermal gradient differences between developed and undeveloped
areas) to minimize impact on microclimate and human and wildlife habitat.
Requirements
OPTION 1
Provide any combination of the following strategies for 50% of the site hardscape (including
roads, sidewalks, courtyards and parking lots):
Shade (within 5 years of occupancy for trees, or per LEED 2009 by solar panels, or by
architectural shading features with a solar reflectance index [SRI] of at least 29)
Paving materials with a Solar Reflectance Index (SRI) of at least 29
Open grid pavement system (at least 50% pervious)
OR
OPTION 2
Place a minimum of 50% of parking spaces under cover (defined as underground, under
deck, under roof, or under a building). Any roof used to shade or cover parking must have
an SRI of at least 29, or per LEED 2009 be a green roof or covered by solar panels. LEED 2009
further clarifies that there is no SRI requirement for parking which is underground, under
a deck, or under a building.
Potential Technologies and Strategies
Shade constructed surfaces on the site with landscape features and utilize high-reflectance
materials for hardscape. Consider replacing constructed surfaces (i.e., roofs, roads,
sidewalks, etc.) with vegetated surfaces such as vegetated roofs and open grid paving or
specify high-albedo materials to reduce the heat absorption.

Calculations and Considerations

Option 1 Option 1 provides for reduced heat impacts from at least 50 percent of the site
non-roof hardscape. This includes all parking areas (spaces, aisles, and other paved