Hello,
I have been going round and round to determine an appropriate EPD to use for steel and aluminium claddings and roofing. Typically I use an average for the material (e.g. CLF baselines) * weight of product but I wanted to check how close that is to actual cladding/envelope EPDs, and for Aluminium it is not close at all!

What are other people using for their aluminium and steel roofing/cladding values?

Aluminium
As a ballpark I have used CLF 2023 baseline of 10.76kgCO2e/kg * 4kg/m2 = 43kgCO2e/m2, but EPDs are giving very different numbers.
MCA Industry Avg EPD: 18.3kgCO2e/m2 (4.91kg/m2) - this seems too low to me
Alu Quebec Industry Avg EPD: 83.3kgCO2e/m2 (18.33kg/m2)
Pac-Clad EPD: 3.8kgCO2e/m2 (2.07kg/m2) - this seems too low to me
ColorCote EPD: 33.0kgCO2e/m2
GDA EPD: 26.7kgCO2e/m2 (7.4kg/m2)

Steel
As a ballpark I have used CLF 2023 baseline of 2.32kgCO2e/kg * 5kg/m2 = 11kgCO2e/m2. The EPDs are not too far from this value.
MCA Industry Avg EPD: 15.1kgCO2e/m2 (2.77kg/m2) - I am happy to use this industry average based on other values
MBMA Industry Avg EPD: 13.1kgCO2e/m2 (4.78kg/m2)
ColorCote EPD: 13.9kgCO2e/m2
Pac-Clad EPD: 15.8kgCO2e/m2 (4.67kg/m2)

Thanks for asking this question. We (Colorado Embodied Carbon Collaborative) are trying to set values like you are (although for life cycle stages A-D), and the metal cladding category is difficult to pin down.

I do have some comments for you:

Aluminum

The kg/m2 you are using of 4 is too high. 2 - 2.5 kg/m2 is probably more appropriate. The CLF baseline for aluminum in the cladding & roofing category is 18.6 kgCO2e/m2. The 10.76 kgCO2e/m2 is for aluminum extrusions which have higher A3 emissions.

I also doubt the Pac-Clad value of 3.8. Note the weight of 2.07 kg/m2.

The MCA EPD has the weights of steel and aluminum switched, so the aluminum should be 2.77 kg/m2. The 18.3 kgCO2e/m2 seems about right at the 2.77 kg/m2.

I would use 18 kgCO2e/m2 for A1-A3 and 15 kgCO2e/m2 for full life cycle.

Steel

The CLF 2023 baseline should be 15.3 kgCO2e/m2 from the Cladding & Roofing section.

The MCA weight should be 4.91 kg/m2, although the 15.1 (15.6?) kgCO2e/m2 is correct.

The MBMA EPD from 4/1/2021 shows 12.33 kgCO2e/m2. I think the MBMA numbers are low.

I would use 15.3 kgCO2e/m2 for A1-A3, and 10 kgCO2e/m2 for A-D.

Thanks so much Bob! I’m really pleased CECC is looking into this further. Embarrassingly I hadn’t realised there was a cladding section to the updated CLF baselines. That might have sped this up!

It’s a shame that MCA messed up the weights of steel vs aluminium in their EPD though! I’m sure this this has thrown others like me off. I’ll use the MCA EPD results, which are the basis of the CLF baselines and your recommendations.

I don’t know enough about the aluminium industry in the US but the MCA results (18.3kgCO2e/m2, 2.77kg/m2, 6.60kgCO2e/kg) are lower than industry averages in Canada (83.3kgCO2e/m2, 10.61kg/m2, 7.85kgCO2e/kg) and Europe (40.5kgCO2e/m2, 4.05 kg/m, 10kgCO2e/kg). Not by much if you look at it on a per kg basis though. Clearly the weight of cladding makes a huge difference.