What is the correct documentation to verify that the pre-engineered steel building contains recycled content?

Most manufacturers should publish a data sheet that outlines their contribution to LEED credit MR 4.1 and 4.2. This can usually be found on their website. The recycled content will vary by component of the building. Steel structural frames will have one percentage , while secondary structurals ( girts and purlins) will have another and roof and wall panels still another. The aggregate of these will then have to be calculated by the building supplier for a specific project based on the cost of each of these components. These percentages also need to broken down by pre-consumer and post consumer content. Butler Builder all have access to this data through Butler Manufacturing Company. The good news is that there is plenty of recycled content in Butler buildings and this will go a long way toward achieving these credits.