For the Materials Credits: (4, 5, 6 and 7), the percentage calculation is based on material costs only (see exclusions). Our project is a publicly bid government project for which only lump sum bid information is available. The general contractor has significant historical data calculating the materials only cost of a project at 60% of the total construction cost. Would it be acceptable to use this formula to prepare our calculations for these credits?
The material credits listed require material cost information for each individual material category (i.e. steel, gwb, millwork, carpet, etc) in order to calculate adjusted values for LEED credits. You will not be able to effectively address these credit requirements if your cost information does not break down costs by material. The value you suggest for total material cost percentage is acceptable if you provide some documentation from the contractor that you are using an estimate in lieu of actual material costs. However, an assumption of 60% might be high, making material percentage credits more difficult to achieve. Version 2.1 of LEED includes some new language about this calculation that may be useful to your project. The new Version 2.1 language suggests a material cost percentage that is lower than you propose. This information should be available shortly on the USGBC website, and could be used by your project once it is published there. Applicable Internationally.