Rating System

LEED BD+C: New Construction, LEED O+M: Existing Buildings, LEED BD+C: Core and Shell, LEED BD+C: Schools

Rating System Version

v3 - LEED 2009, v3 - LEED 2008, v2 - Schools 2007, v2 - LEED 2.2, v2 - LEED 2.0

Inquiry

Many CIRs address the fact that you can use the weighted average method outlined in the SSc7.1 CIR dated 12/5/2001 for SSc7.2. That CIR outlined a baseline which assumed 30% of the site met the 0.3 reflectance requirement, and 70% did not. However, the NCv2.2 Reference Guide for SSc7.2 outlines a weighted average calculation which differs from the SSc7.1 method in two ways. The first is that the outlined baseline (75% w/ SRI of 78 & 25% w/ SRI of 30) requires that 100% of the roof area is compliant with the SRI requirements. Also, the outlined baseline assumes that 75% of the roof area is low sloped, and 25% is steep sloped. If a project has a low slope for 64% and a steep slope for 36% of the roof area, can we use a baseline weighted average which reflects our ratio of steep to low sloped roof? Also, can we use a baseline weighted average calculation which requires 75% of the roof area to be compliant instead of 100% of the roof area? I\'ve outlined an example below: If 75% of the low sloped roof is compliant, for our project this would mean 48% (64%x0.75) of the total roof area should have an SRI of at least 78. If 75% of the steep sloped roof is compliant, this would mean 27% (36%x0.75) of the total roof area should have an SRI of at least 29. Since 48% + 27% = 75% of the total roof area, this method reflects credit requirements and is consistent with the weighted average methodology outlined in the SSc7.1 CIR. Therefore, the weighted average baseline would be: 27% x 29 + 48% x 78 = 45.27 Can this calculation methodology be used to calculate the baseline for the weighted average option for SSc7.2?