His main point still holds true: XPS and ccSPF with high-GWP blowing agents have a much longer (and often onerous) GHG payback.

The assumptions needed to quantify this go beyond the GWP of the foam to the aspect ratio and orientation of the particular building, the heating and cooling systems, and the occupancy patterns. His point is well understood by the industry: avoid spray foam until the manufacturers improve the GWP of their product.

Now it’s up to the manufacturers to present clear, verifiable information about what types of materials and improved blowing agents they’re using so the building industry can confidently use their products.

First, a dish of calamari has long been one of my favorites and there’s been an approximate 1-in-3 chance the “hogs’ anus” comment is made since that radio program aired. Now, the 1-in-3 is not scientifically verified (this is from memory) but is also from a specific sample of my dining companions (who are probably more likely to listen to This American Life than a random sample of US Residents). So my graph will not necessarily represent total US back-talk and will likely fail a peer review.

I poor digression on this to address your second point: determining some vague ‘payback’ for global warming based upon materials choices. Absolutely Alex Wilson’s graph includes a large set of assumptions. There’s a complimentary chart in the same report which provides the numbers for many of them, from R-per inch to Embodied Energy to the final column which lists GWP per sq.ft.of R. Why I utilize this diagram is to represent the relative impact of ingredients, not to define a specific payback (how can one quantify a payback without including the source of the energy which is being off-set by efficiencies?) Relatively, ccSPF and XPS ingredients have a significantly greater GWP than the competing products. Maybe we should sit down and put together a graph with altered assumptions, but the divergences between the lines will still be large, no?

The word from an insulation colleague is that Honewell’s Solstice blowing agent will be pretty universal for ccSPF by the end of 2017, at least in our region. The XPS manufacturers are slightly cleaning up their act (down to a GWP of ~800) but they still will not follow the lead from European regulations which already have significantly lower numbers.

Maybe you misunderstood what I’m saying. I’m speaking about existing housing stock that has been built over the last 20-25 years and not likely to be torn down any time soon. In the U.S. the walls of these homes are typically stick built with 2×4’s 16″ OC, fiberglass insulation, house wrap may/may not be there and the siding is nailed directly to the sheathing (no rainscreen).

Retrofitting the typical 1990’s tract built house to PH standards isn’t impossible given enough $$. Anything is possible with enough $$, but in the U.S. it seems that exterior rigid foam board offers the current homeowner the best bang for the buck. Especially in mixed-humid climate.

kris, thats so not true! It
kris, thats so not true! It seems (not to be offensive here) an ignorant comment …where is your proof of that? And I suppose I have to come up with a backlash of info for my comment, but all you have to do is study Passive House methods and testing, and that will prove you wrong!

Andrew, everything you’ve
Andrew, everything you’ve said is fine. I have no problem with someone arguing that you shouldn’t use ccSPF or XPS because of the possible use of blowing agents that may be bad for global warming.

What I do have a problem with, though, is Wilson’s attempt to quantify a payback when his calculations were based almost entirely on assumptions. There’s a good reason he didn’t include quantitative uncertainties with his results: They probably would have shown that his results had no scientific significance. Using a different set of assumptions could yield wildly different results.

Nice slide show, Lloyd. I don
Nice slide show, Lloyd. I don’t know what you said with each slide, I didn’t see Wilson’s graph in there anyway, so I’m sure it was fine.

I think you haven’t heard
I think you haven’t heard much because they’ve been slow to switch. It’s not a simple matter of pulling the old blowing agent and using the new one. The new one requires adjustments to the formula. I think you’ll see more companies making the move soon. Lapolla has done so with high-pressure systems already. Fomo has made the change with their low-pressure foam.

Spray foam, like every other
Spray foam, like every other product, has its pros and cons.

That’s an installer issue,
That’s an installer issue, Kris. I’ve seen — and posted — photos of ccSPF pulling away from framing members. Most installations are fine, though.