I've got a project with 40% cement substitution (4 mix designs) with fly ash and I thought I would take the opportunity to calculate the recycled content value of fly ash as a percentage of the SCM's only as I thought it would help our recycled content numbers. I typically calculated it as a percentage of the whole mix design.
Here's the issue - if I want to count the concrete materials as regional (and I do), I have to add back in the value of the non-SCM's - stone, sand, etc.
Is this correct - am I missing something?
This essentially defeats the purpose of isolating the SCM's in the first place. Other concerns about fly ash content aside, the production of cement is responsible for over 12% of the world's carbon emissions. Am I the only one who thinks it is ludicrous to think that 'environmental value' is linked in any way to material cost, percentage weight, or any of the allowable methods to give it LEED material credit?
(yes, we will take an ID point - but the structural engineers who struggled to give me 40% will not be happy when they realized how little it did for our LEED rating)
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Nadav Malin
CEOBuildingGreen, Inc.
LEEDuser Expert
844 thumbs up
January 27, 2014 - 1:59 pm
Hi MIchele,I think what you're describing is right. The way I like to think of it, when you choose to do the SCM calc's separately you're essentially taking one product (concrete) and dividing it into two (SCMs and the rest of the concrete ingredients).So you can get the local materials credit for the aggregates either way, but they'll have a lower $$ value if you've separated the SCMs out.In response to your point about CO2--yes, that's the very reason this special calc method was introduced--to provide a way to get some non-trivial LEED point contribution for cement substitution. Within the context of LEED 2.2/2009, that was the only option. In v4, there is the Whole-building LCA credit, which should address this issue much more directly.
Michele Helou
PrincipalSage Design & Consulting
72 thumbs up
January 28, 2014 - 7:56 am
thanks Nadav - I rechecked my math with each option. Isolating the SCM's does give me $17,200 dollars of recycled content value versus $10,400 using the traditional way by weighted percentage of the whole mix design - (not including the water in the fly ash percentage of the mix). But the total material value of the concrete is $167,000 - so it's really only at 10% for MRc4 - and my goal was 30% - so in a way - the concrete at 40% fly ash is not helping. My thought from this is that each material should be judged on a baseline - not how the math of materials you would have used anyway adds up. I suppose that is what the EPD's will eventually do. With the LCA credit on building envelope in v4 - I think that will be a very involved undertaking for most projects at least at first. But if the studies that are done are published - its true value will be educative.
Susan Walter
HDRLEEDuser Expert
1296 thumbs up
January 28, 2014 - 8:46 am
Have you looked at getting the EP credit for Regional instead of Recycled Content? We do most of our projects with concrete structures and find we easily earn the Regional EP and struggle to get to the 20% threshold for Recycled.
Michele Helou
PrincipalSage Design & Consulting
72 thumbs up
January 28, 2014 - 12:03 pm
thanks but it's a steel structure - this concrete is just the slabs on metal deck. the steel came from US Nucor plants - on this continent - but not within 500 miles.
Keith Lindemulder
Environmental Business Development- LEED AP BD&CNucor Corporation
193 thumbs up
January 28, 2014 - 12:35 pm
Michele, Depending on the project you should have significant value for both MR4 and MR5 with a good mix of steel and concrete. Feel free to send me an email if you'd like me to look over our products. keith.lindemulder@nucor.com(link sends e-mail)
Matthew Martin
Assistant Site SuperintendentQBS, Inc.
3 thumbs up
May 12, 2014 - 4:40 pm
I'm also trying to receive credit for the recycled fly ash in our concrete. I've determined it is 33% and 29% by weight and volume respectively. Am I right in assuming the fly ash is simply 33% of the total cost of the concrete and that I can still use the fly ash cost and the remainder of the concrete cost as regional materials. I wasn't expecting to separate the concrete further into it's sand, aggregate, and water components because those components invariably come from the same location. Is this the right approach?
RETIRED
LEEDuser Expert
623 thumbs up
May 13, 2014 - 8:58 am
Matthew - The short answer to all your questions is no. Fly ash is calculated differently than other materials. Its weight (mass) is only compared to the weight (mass) of the other cementitious materials - not the entire mix. Ideally you need the weight of all components in the mix (or at least the fly ash and cement) to calculate fly ash’s contribution.
Please consider opening this URL to see all the comments for this forum and then search for fly ash to further assist you - http://www.leeduser.com/credit/NC-2009/MRc4?all-comments=true.
This one on Cementitious Materials Calculations from November 2013 should be of assistance but you really need the Reference Guide to be most effective - http://www.leeduser.com/credit/NC-2009/MRc4?all-comments=true#comment-44721.