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Pro and cons of 1-part vs. 2-part foams

Geoff_Frood | Posted in Energy Efficiency and Durability on

I’m in the middle of a new construction and have been using both 2 part foams and 1 part foams to seal around openings. Is there any advantage of one over the other? The only difference I can see is that the two part cures very quickly, sometimes too quickly, but the mix goes out of wack at in the last 15% of the tanks. Is there a substantial difference?

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  1. GBA Editor
    Martin Holladay | | #1

    One-component foams are "moisture-cured" (they pull moisture from the air to cure chemically -- in very dry weather, this can be a problem). For more information on one-component spray foams, see Justin Fink’s Canned Spray Foam Tip.

    Two-component foams cure chemically regardless of the moisture content of the air.

    Your experience -- that "the mix [of two-component spray foam kits] goes out of whack in the last 15% of the tanks" -- is not typical. Make sure that your tanks are kept warm -- cold temperatures interfere with application and curing -- or consider buying another brand of two-component foam.

  2. charlie_sullivan | | #2

    Two more differences:
    1) Two part uses HFC blowing agents with extremely high global warming potential, whereas one part foam uses hydrocarbons (e.g., pentane) which have less than 1% the global warming potential in comparison.
    2) When two part foam goes out of whack, most likely because of temperature problems, there can be lingering odors.

    For those two reasons, I don't see a role for two part foam in green building. The only caveats I would add is to make sure there is moisture available for the one part to cure as per the tip Martin linked, and to limit the application to reasonably small volumes, because the blowing agent is flammable. If you tried to fill a wall cavity with one part, you might end up with enough flammable blowing agent in the room that a spark could result in an explosion.

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