Page 102 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED Sustainable Sites 83

Criteria for Option 1 Option 2
Credit point HS/2 ≤ (S + R + O ) CP ≥ TP/2
mod mod
(At least one-half the hardscape is (At least one-half of the parking
∗
specially adapted to reduce the heat spaces are covered ).
island effect.)
EP point HS = (S + R + O ) CP = TP
mod mod
(All the hardscape is specially adapted (All the parking spaces are
∗
to reduce the heat island effect.) covered ).
∗ If covered with canopies then these must be covered with solar panels or have an SRI of 29 or greater.

TABLE 2.7.2 Summary Criteria Equations for Heat Island Effect: Non-Roof LEED 2009

of Portland cement and fly ash (up to 25 percent). This use of fly ash is promoted as an
environmental benefit as it recycles waste from another process which might otherwise
be landfilled, and it also promotes a reduction in the use of energy and the production
of carbon dioxide from the cement-making process. However, concrete with fly ash is
usually darker than concrete made with only Portland cement. Therefore, it may be
beneficial to use concrete for surface treatments that either have no fly ash or are coated
to lighten the surface color and promote reflectivity, whereas it may be good to use
concrete with fly ash for other site applications to aid in earning other credits.
If there are special circumstances or considerations for this credit, a narrative must
be submitted describing these circumstances.
An EP point may be awarded if it can be demonstrated that either of the options is met
with a 100 percent requirement. For Option 1, this means that all the non-roof hardscape
surfaces have been constructed with high-SRI materials, shaded within 5 years, or open
grid paving systems as previously defined. For Option 2, this means that all on-site parking
spaces are located under cover as required in the credit.
A summary of the equations for credit compliance and awarding of an EP point for
either option is presented in Table 2.7.2.

SS Credit 7.2: Heat Island Effect—Roof

USGBC Rating System
SSc7.2 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 for LEED 2009 as noted:

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
Use roofing materials having a Solar Reflectance Index (SRI) equal to or greater than:
• 78 for low-sloped roofs (slope ≤ 2V:12H)
• 29 for steep-sloped roofs (slope > 2V:12H)