Heat Island Reduction Credit Changes in LEED v4
Project teams are allowed to register for either LEED v4 or LEED 2009 until June 1, 2015, after which LEED v4 will be the required rating system. USGBC has made some changes to the Heat Island reduction credit requirements for version 4, which are:
- Combined Sustainable Sites credits 7.1: Heat Island Effect — Non-Roof and 7.2: Heat Island Effect – Roof into a single credit SSc5: Heat Island Reduction.
- Increased the SRI requirements for cool roofing materials
- Included 3-year aged SRI/ SR values as an alternative option for product qualification
- Incorporated a weighted average SRI calculation methodology
- Changed the metric by which hardscape paving materials are measured from SRI to Solar Reflectance (SR)
- Increased minimum percent of parking spaces under cover from 50% to 75% to qualify
- 1. U.S. Green Building Council (2009). Heat island effect – roof. Retrieved May 29, 2014, from http://www.usgbc.org/node/1731100?return=/credits/new-construction/v2009
- 2. U.S. Green Building Council (2012, October 4). LEED Reference Guide for Green Building Design and Construction with Global Alternative Compliance Paths. Retrieved June 3, 2014, from http://www.usgbc.org/sites/default/files/LEED%202009%20RG%20BD+CSupplement_GLOBAL_12_2013_Heat_Island_Update.pdf
What SRI values do Building Materials need for LEED?
As shown in Table 1, the minimum SRI for cool roofing has increased in the newer LEED v4. In the earlier LEED 2009 requirements, cool roofing did not consider aged SRI as an option for qualification. Projects seeking LEED v4 have the option of qualifying using either initial SRI or by obtaining the 3-year aged SRI value. Surface Optics does not perform aged SRI testing.
|Table 1. Minimum SRI for Cool Roof Materials in LEED 2009 vs. LEED v4|
|Slope||Initial SRI||3 year aged SRI|
|LEED 2009||Low sloped roof||≤ 2:12||78||—|
|Steep-sloped roof||> 2:12||29||—|
|LEED v4||Low sloped roof||≤ 2:12||82||64|
|Steep-sloped roof||> 2:12||39||32|
The impact of hardscape such as roads, sidewalks, courtyards, and parking lots is an important element in earning the Heat Island reduction credit. Table 2 shows the requirements for hardscape and shade providing architectural devices and structures. In LEED version 4, paving materials require documentation for Solar Reflectance only, not the SRI asked for in LEED 2009.
|Table 2. Minimum Solar Reflectance for Hardscape in LEED 2009 vs. LEED v4|
|LEED 2009||Solar Reflectance Index||29||—|
|LEED v4||Solar Reflectance||0.33||0.28|