Sometimes the guidelines we set and attempt to live by simply cannot be followed every single time, and although we may strive for 100%, we may need to be content with somewhere in the mid-to-high realistic range.
I’m talking about best practices, of course, not federal/state/municipal laws, nor ethics, nor values.
I think the biggest disconnect that exists is simply the lack of education, even within the construction industry itself, about the vast differences among products.
My personal standard has always been to avoid closed-cell spray foam with traditional blowing agents in favor of HFO blowing agents. Not a problem here; this is something that’s planned in advance with the spray foam people.
The second part of my personal standard has been to avoid sheet XPS products for the same reason.
(As a reminder, both of the products I avoid have a GWP that is in excess of 1,000 times that of an equivalent weight of carbon dioxide.)
But I recently needed high-compressive strength foam for forming and insulating three column footings and I didn’t have time to wait several weeks for the high-compressive strength EPS product (favorable GWP of around 10 or less) nor did I need or want to purchase an entire pallet of it – I needed 2 sheets, 4×8 feet in size.
Q: Why didn’t you simply use wood to form the column footings (referring to picture)?
A: Our old enemy, thermal bridging (read more here). You may be inclined to say that there’s not much heat loss to Mother Earth as she typically stays at a constant 50-55 degrees F.
But that’s erroneous thinking – because the heat loss isn’t solely related to the temperature gradient, it also is related to the surface area in question. And Mother Earth immediately below grade (at least in climate zone 6 where this project is located) isn’t likely to be as high as 50 degrees F.
We needed to insulate and form for the column footings, preferably with one product.
Q: Why couldn’t you simply wait for the framing crew?
A: Because they want to get in, do their work, and get out. They don’t have time to wait for concrete to cure and reach appropriate compressive strength to support a load when they’re on the jobsite.
Lo and behold, Home Depot had high compressive strength XPS available on the shelf.
I bought 2 sheets.
I used 90% of the 2 sheets.
It doesn’t matter how much I used; the GWP is determined by production of the materials. In essence, I committed them to use.
According to heat-sheet.com (see references below), using XPS instead of EPS high density foam in a 1,600 square foot slab will cost an equivalent of 52,000 pounds of carbon dioxide emissions.
Wow. That’s significant.
For my transgression, 64 square feet translates into 2,080 pounds of carbon dioxide emission compared to a more favorable product.
According to usda.gov, a mature tree will absorb approximately 48 pounds of carbon dioxide from the atmosphere and release oxygen.
Therefore, if I’m looking for a break-even point between “equivalent carbon emissions” and “carbon sequestration,” and I consider a 10 year period (a tree will have a life cycle longer than 10 years but you can’t plant a mature tree), 2,080/48/10 = 4.33 trees I will have to plant to become “carbon neutral” when normalized for carbon dioxide.
This is for having been responsible for the emission of HFC blowing agents within our atmosphere (but it’s easier to speak the carbon dioxide language when you want to quantify and make comparisons).
Hey, not bad. But I also removed 2 trees that were in my way on the job, so now I need to plant 6.33 trees.
OK. Duly noted. (Landscaping comes later).
Q: What about all the other types of insulation you plan to use on this build?
A: Great question. I’ve planned in advance for all the other areas where insulation is needed. Polyisocyanurate (low GWP), mineral wool (low GWP), dense packed cellulose (this has a negative GWP as it’s recycled material), and HFO-blown closed-cell spray foam (minimal GWP).
I shouldn’t get caught in a do-or-die situation again!
You may be inclined to disagree with the concept of global warming, but I think we all will agree that climate change and climate absurdities are becoming more prevalent and commonplace.
And the more responsibly we can build, the more carbon sequestration we will have “in the bank,” so to speak.
On a related note, good news! Dupont is going to make lower-GWP XPS sheet foam.
In a self-published article, it claims “DuPont Encourages and Demonstrates Transparency Throughout Rollout of Low-GWP Insulation Materials in North America.”
The problem is, Dupont never acknowledges what the actual GWP is for the new product.
On another webpage, they talk about how they’re going to reduce emissions by 75% by 2030.
The problem is, they don’t tell you from what to what…75% reduction of a massively horrendous number is still potentially a massively horrendous number.
I’m not picking on Dupont. Good for them for working to lower the GWP. I wonder if Owens-Corning, the maker of the board insulation that I purchased, is working on the same thing.
I am picking on the vagueness with which information is presented, as if you (the reader) and I (the author/developer and green building stalwart) aren’t capable of our own analysis and require that data be spoon-fed to us by the very entity who profits from the promulgation of this data.
Side note: there is apparently a website on which I can register and then view the product performance attributes. It was giving me trouble registering, then when I tried again, it told me the email address already existed. Sigh.
I was able to access the product technical specifications, but there was only mention of R-value (gimme a break, everyone already knows the R-value of XPS foam is 5 per inch) and nothing about GWP.
But Dupont is in Midland, Michigan, 20 miles west of me. Close enough to harass them until I get the data I want.
Oh, well. No need to let my blood pressure get too high. I’ve got 6.33 trees to select and place. And I’m still recovering from mixing 23, 80 pound bags of concrete by hand.
Until next time,
Dr. Lee Newton
How A Doctor Learned To Develop Real Estate