We have a supplier's documentation spreadsheet for structural steel listing each separate material (HSSs, beams, channels) with weight, cost, post and pre-consumer percentages. If we want a single value to place in our master product value spreadsheet for structural steel we have two options:
1) If each line item already has a listed recycled content percentage, those should already have been calculated by weight for that item, and we should average all the structural steel line items by their individual costs, correct? This would be analagous to putting each steel member individually in the master product value spreadsheet.
2) Alternately, the sum of the line items could be averaged by weight, but that's normally done only for assemblies, and would in effect be double-calculating the recycled content by weight which could skew the values slightly.
The confusion arose because our material information sheets ask for the percentage of recycled content within a (single) product by weight. The supplier then calculated the average of the structural steel line items' recycled content by weight, based on the confirmed recycled content (by weight) of each item.
If we had not seen the individual cost column, we would not have noticed or asked the question. I'm sure this frequently happens in the background when we receive only one final figure. Is option 1) above the correct method?
RETIRED
LEEDuser Expert
623 thumbs up
May 3, 2013 - 5:26 pm
Erik - I’m going to respond with a couple of questions back to you. First, why do you want to place a single value in your master product spreadsheet for structural steel? I would think that since you have information delineated by 3 types of products you would just list each one and provide the spreadsheet (or a PDF of it) as supporting documentation to back up your claims.
Is your structural steel something less than 100% steel? As I understand it, weight does not come into play except with assemblies so weight in this case is superfluous if your product is NOT an assembly. Please see MRc4’s Calculations and Calculating Assembly Recycled Content in the LEED Reference Guide for Building Design and Construction for more information.
Erik Heck
Mission Green BuildingsMay 3, 2013 - 6:28 pm
Thanks Michelle - Each type and size of structural member are line items - we have 35 entries for steel and combining them to product one number for structural steel (with the spreadsheet breakdown as backup) made sense.
The steel supplier had already combined them by their weight and varying recycled content percentages (Option 2), but as they are not an assembly, we changed that to a cost-based calculation (Option 1), rather than weight.
The structural steel is 100% steel. The recycled content of each item would have already been calculated by weight to provide their initial percentages (i.e. recycled vs. virgin material).
Averaging all the steel items by weight to produce an overall steel figure (Option 2 and supplier's initial calculation) seems like it would skew the values, as there is not a 1:1 ratio between cost and weight for the different products.
RETIRED
LEEDuser Expert
623 thumbs up
May 6, 2013 - 9:51 am
Thanks for the clarification. I agree that using the weight calculation for a non-assembly product is not the right way to go.
And I now understand why you want to simplify 35 entries - although I still think it might be clearer to group those 35 items into a few categories vs. lumping them all together. However, either way you go, I would strongly suggest that you initially provide backup to GBCI so that you can show your methodology from the beginning.