Great Stuff doesn't look ideal, since it's going to get a lot of sunlight on the outside, and Duct Seal doesn't say anything about whether it actually insulates.
Also, the Duct Seal material safety sheet doesn't really convince me that it's %100 non-toxic to inhale, and I am somewhat sensitive to chemicals. I'd like a really green alternative. Mycelia?
Note–this is a different situation from the question "How should I fill a hole in an exterior wall?" since I have no cables running through the hole and simply want the hole filled and insulated. I live in a cold climate. Thanks much.
Best Answer
you don't say what the material is that has a hole in it. Great Stuff works well usually. Let it dry completely (for like a day or two). Hack saw blade (no saw) cuts off excess flush with surface. May want to push in filler to create a dent to allow for cap/finish agent. Spackle/skim over with your favorite skimming agent (something that matches existing surface). I have used vinyl spackling for smooth stuff and sanded, cementicious products for stucco and rock, I'ved used Bondo, Durham's Rock Hard...etc., etc. Great stuff is your insulator and filler then you just need to skim/cap/finish it then paint it.