SpecTopics: Heat Island Reduction Credit and LEED® V4/V4.1

It seems there are some misconceptions in the marketplace when it comes to achieving the Heat Island Reduction Credit for LEED® Building Design and Construction (BD+C) V4 and V4.1. To help provide clarity, this SpecTopic is all about white reflective roofing and its role in the Heat Island Reduction Credit.

Let's review the credit. To achieve the credit, there are 2 options. (The italicized text below is reproduced from the LEED V4/4.1 Reference Guide for Building Design and Construction [BD+C]).
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Option 1. Nonroof and Roof (2 points except Healthcare, 1 point Healthcare)
Meet the following criterion:



Nonroof 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. Install vegetated planters. Plants must be in place at the time of occupancy and cannot include artificial turf.
• Provide shade with structures covered by energy generation systems, such as solar thermal collectors, photovoltaics, and wind turbines.
• Provide shade with architectural devices or structures. If the device or structure is a roof, it shall have an aged solar reflectance (SR) value of at least 0.28 as measured in accordance with ANSI/CRRC S100. If the device or structure is not a roof, or if aged solar reflectance information is not available, it shall have at installation an initial SR of at least 0.33 as measured in accordance with ANSI/CRRC S100.
• Provide shade with vegetated structures.
• Use paving materials with an initial solar reflectance (SR) value of at least 0.33.
• Use an open-grid pavement system (at least 50% unbound).

High-Reflectance Roof Measure
Use roofing materials that have an aged SRI equal to or greater than the values in Table 1. If aged SRI is not available, the roofing material shall have an initial SRI equal to or greater than the values in Table 1.

Table 1. Minimum Solar Reflectance Index (SRI) Value, by Roof Slope
Roof Slope Initial SRI Aged SRI
Low-Sloped Roof ≤ 2:12 82 64
Steep-Sloped Roof > 2:12 39 32

Roof area that consists of functional, usable spaces (such as helipads, recreation courts, and similar amenity areas) may meet the requirements of nonroof measures. Applicable roof area excludes roof area covered by mechanical equipment, solar energy panels, skylights, and any other appurtenances.

Vegetated Roof
Install a vegetated roof using native or adapted plant species.

OR

Option 2. Parking Under Cover (1 point)
Place a minimum of 75% of parking spaces under cover. Any roof used to shade or cover parking must (1) have a 3-year aged SRI of at least 32 (if three-year aged value information is not available, use materials with an initial SRI of at least 39 at installation), (2) be a vegetated roof, or (3) be covered by energy generation systems, such as solar thermal collectors, photovoltaics, and wind turbines.

The credit calculations must include all existing and new off-street parking spaces that are leased or owned by the project, including parking that is outside the project boundary but is used by the project. On-street parking in public rights-of-way is excluded from these calculations.
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After reviewing the text above, it is clear that unlike the previous version (LEED 2009), which focused on the roof itself for the Heat Island Credit, the newer version of LEED (V4 and V4.1) is concerned with the entire project site.

The project site includes the building's roof, parking lot, roadways, walkways, and other hardscapes. To achieve the 1 to 2 points for the Heat Island Reduction Credit, a designer or building owner needs to address more than the roof. If the hardscapes are not intended to or able to meet the above requirements, then the roof does not need to meet these requirements either, as the credit will not be achieved by the roofing alone.

Also take notice that roofing and vegetative roofing have been added as an option for covering not just the building, but the parking lot, or shading above walkways. This opens the possibilities for more diverse use of roofing materials extending outside the building footprint.

For more information about Carlisle's roofing membrane selection and Roof Garden vegetative roofing systems, visit the Carlisle SynTec website.

Click here for a brochure with information about all of Carlisle's available systems.

Contact Craig Tyler with questions.