It’s expensive and takes some practice but it’s probably the best insulation there is

Keep the tanks above 90 degrees if you can when your spaying. Wrapped in an electric blanket is very common. Below that, you will lose product. Most of my contractors keep the tanks around 100-110 degrees. I know personally its easy to only have 70-80% of the product spray out of cold tanks

Exactly right.

There is a temp gauge on the side of the Froth pack 200 that shows internal temp of product. They recommend not applying with product under 75 and higher is better. I used a heating pad in Canada to bring tanks up above 75, not much above but I was under the gun so I sprayed it.

Have all you electric done first and plumbing too. A friend has that service and it cost him $500 to clean his machine. That is why he laughed.......jk

Pink Panther to the rescue! Going with 2 layers of 1 1/2", which will be R15. Two sheets and 2 cans of Great Stuff about $80 total.

Dry fitting in progress. Am using a hot wire foam cutter to make the channel cuts around that metal brace.

If it were me, I would leave the 1/2" air gap between the two 1 1/2" layers.

Had already thought about that......thinking a bit of dead air between the panels wouldn't hurt. For some reason, seems the gap is more like 1/4" than the 1/2" math says ought to be there. Leaving just enough gap between foam board edges, studs, sill and plate to fit the Great Stuff tube into to get it all the way to the back.

Not sure if where you are at and the climate you’re in. But if you leave an air gap, make sure you air seal all the edges completely so air doesn’t exchange. Foam density varies a little, but R value at about 6 per inch. Having only R9 can allow condensation when it hits the dew point. That’s the huge advantage to the spray foam. Air doesn’t infiltrate through the foam. So even if it hits dew point internal in the foam, no moisture can accumulate.