Schools 2009 SSc7.2: Heat Island Effect—Roof

Check the comments under LEED NC 2009 SS 7.2 "new equation ...". It will give you the source and link to the calculator.

Thanks Susann, but I still don't seem to be getting something... The link provided in "new equation..." is for Option 3 (https://www.usgbc.org/ShowFile.aspx?DocumentID=9757), which requires the calculation including the roof areas and SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. values (required and actual), divided by .75 plus the green roof area (not included whatsoever in the calculator provided) divided by 0.5; to be greater than or equal to the Total Roof Area. The calculator presents a theoretical SRI value that should be met (As in Option 1 if you play with the equation a bit) and I simply do not see how this is consistent with credit language for Option 3, as suggested by the link provided in "new equation...". The problem seems to be that the calculator shows our project has not met the requirements, but using the "new equation..." shows that we have met the requirement with room to spare. I would be happy to share the spreadsheet I created (based on the Addendum to SSc7.2 Option 3) if anyone is interested, but I am hopeful we can resolve this apparent inconsistency. I also suggest that the calculator be amended to have tabs for calculating Option 1 & 3 to avoid confusion and provide more utility to LEEDuser subscribers...

I can't say much to the though process behind the new addendum. However it's official since August 2011 and you can apply it to your project. So if you meet the requirements for option 3 as describe here http://bit.ly/tA3OoO you should be fine.
As for your spreadsheet. I'm sure Tristan from LEEDUser would be happy to share it with our community. Just contact LEEDUser through the contact form.