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Community and Q&A

HFC versus HOC spray foam

Matt_Salkeld_PEng | Posted in General Questions on

Demilec and other spray foam manufacturers are using HOC a zero GWP blowing agent.

Does anyone know the ecological impact of these newer HOC spray foams? They claim the life cycle embodied carbon emissions are much lower because HFC has a GWP of 1,000.

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  1. Matt_Salkeld_PEng | | #1

    An example here they state a 99.9% reduction in the product's total GWP versus HFC equivalent ,

    It wouldn't seem to capture all the other emissions of a hydrocarbon or even soy based foam, the extraction of fossil fuel and the manufacturing and transport.

  2. Expert Member
    BILL WICHERS | | #2

    I don’t think the switch away from HFCs is for global warming potential (GWP) reasons. I think it is because of the “other” issue with these materials which is the ozone depletion potential (ODP). This concern comes up with refrigerants too, and some of the blowing agents used in the foam insulation materials are also used as refrigerants.

    With refrigerants, there are some tradeoffs between the two, such as R123 being very efficient so it has a lower GWP but higher ODP compared with R410A. There is some argument as to which is the bigger issue (I argue ODP is, in this case, because of the energy consumption being less over the life of a R123 chiller).

    As far as I know, there is no standardized way to compare total embodied carbon between products. I personally don’t like to think in terms of “carbon” with energy savings though because it really isn’t equivalent and varies greatly based on where you live and the generation mix in your region.


  3. MattJF | | #3

    The blowing agent change from HFC to HFO does appear to actually be a 99.9% reduction in global warming potential. They are certainly not accounting for the global warming effects of the polymer component. I have 650lbs of plastic stuck to the underside of my roof deck, which I don't love the idea of (there is another 1800lbs of rockwool stuck under that).

    The prices of HFO products seems to be coming down as they become more common. Particularly when the factoring in the ticker lifts it can be applied in.

  4. Matt_Salkeld_PEng | | #4

    Thanks for your replies that's helpful. We are also suggesting flash and batt approach to get the sealing benefits of one or two inches of spray foam along with a batt product inboard.

    1. Expert Member
      Michael Maines | | #5

      Matthew, the global warming potential of HFO-blown foam is not zero, but between 1 and 5, depending on the product and the testing. While that is obviously much better than the GWP of 1030 that HFC-blown foam represents, both are calculated on a 100-year scale. Climate scientists say we don't have 100 years to make up for the up-front emissions; on a 10- to 20-year scale, HFO-blown looks much worse. Using a flash and batt or flash and fill approach is a good compromise--just make sure the ratio of foam to batt is high enough to prevent moisture accumulation.

      Side note, someone above mentioned the ozone layer--no foam currently has ozone-depleting compounds, so it's a non-issue.

  5. Expert Member
    Dana Dorsett | | #6

    Eyeball the bar graphs showing the relative CO2e between HFC blown and HFO blown closed cell foam here:

    It's not even a reduction by half, at any given R-value.

    Going with water blown half-pound open cell foam (not shown in that graph) would be about a 2/3 reduction (at given R-value, not thickness) It takes 2" of HFO blown close cell foam to match the R-value of 3.5" of half-pound foam, but there is only about 2/9 the polymer content (less than a quarter) in that 3.5" open cell foam as there is in 2" of HFO blown closed cell foam.

    Closed cell is far more vapor retardent than open cell, but unless you absolutely need the lower permeance of closed cell foam, open cell is by far the lower environmental footprint. Whenever it can be designed out (which is pretty much always, in new construction) it's better to just not use closed cell spray foam.

    In many applications 1lb density polyiso performs about as well as closed cell spray polyurethane, using only half the polymer content (a closely related chemistry to polyurethane) , and only low-impact hydrocarbon blowing agents.

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