Page 101 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

82 Cha pte r T w o

concrete and weathered asphalt pavements, and weathered and new concrete
pavement surfaces, respectively.
• Open grid pavement systems. Variable O is defined as the area of the hardscape
which is covered in open grid pavement systems which are at least 50 percent
pervious with vegetation in the open cells.

The three pathways for reducing the heat island effect by keeping at least 50 percent
of the non-roof hardscape as shaded, high SRI, or open grid cannot be superimposed on
one another. In other words, an area that is both shaded and high SRI cannot be counted
twice. There is some discretion with the shading value as it is an arithmetic mean of
various areas determined by the angle of the sun, and if there is any question as to whether
the appropriate areas are used, then these should be well documented. The easiest way to
perform the calculations is to give modified definitions for R and O such that
R R is the sum of the areas with high SRI excluding those areas that are shaded.
mod mod
O O is the sum of the areas with open grid pavement systems that are not
mod mod
shaded or do not have high SRI values.
By using these definitions, compliance with Option 1 can be determined if the following
inequality is true:

HS/2 ≤ (S + R + O ) (2.7.1)
mod mod

Option 2 The calculations for Option 2 are simpler. First determine the total number of
parking spaces (TP) for the project and then count the number of these total spaces that
are under cover (CP) for which the top roofing material above them has an SRI of at least
29 or is covered by solar panels or vegetation if under shading devices. Under cover
includes underground, under the building, under a deck, and under shade structures
such as canopies. If more than one-half of the parking spaces are under cover as so
defined, then the credit is met. Note that this option only refers to the parking spaces
themselves and does not mention anything about the parking aisles or other paved areas
associated with these spaces. The equation for compliance with Option 2 is

CP ≥ TP/2 (2.7.2)

Special Circumstances and Exemplary Performance
Submittals for both options should include the calculations for each option. In addition,
for Option 1, the submittals should include site drawings showing all the non-roof
hardscape areas with their heat island–related characteristics (shading, SRI, or open grid)
and areas noted. The surface SRIs given may either be the actual for each paving material
or as provided for similar mixes and ages on other projects. For Option 2, the submittals
should include plans with the number of total parking spaces and parking spaces under
cover with the appropriate roofed SRI or solar panel if under canopies. Option 2 is a great
example of how design team members need to work together to obtain the LEED credits.
The parking layout may sometimes be determined by others than the architectural roofing
designer. Only together will this option be met.
Concrete is a common material used for many surface treatments and other
structural components of the built facilities. Many concretes are made with a combination