FSC calculations - weight or volume?

Hi Jean - The FSC contribution to the credit is based on cost as the credit requires at least 25% (by cost) of the total value of permanently installed building products. However, I assume you may actually be asking how you might break out the different components (non-wood materials) of an FSC certified product to determine the cost contribution to the credit. For this information, please read the MR Credit Category Overview information on the following link: https://www.usgbc.org/guide/bdc#cc_overview Under the header for “Determining Material Contributions of an Assembly”, you will find that LEED requires you to determine the contribution of the FSC component by looking at weight of the FSC wood as a percentage of the entire product. You will then apply this percentage to the overall product cost to get the cost contribution to the credit. Lastly, FSC Mix Credit and FSC Mix % products are both FSC certified products and can contribute to LEED credits. Wood products that are identified on invoices as FSC Mix Credit are valued at 100 percent of cost. Wood products identified as FSC Mix NN% are valued at the indicated percentage of their cost (e.g. a product identified as FSC Mix 75% is valued at 75 percent of the total cost).