The Energy Vanguard investigates an attic insulation job in Charleston, SC. #TheBadNews: it is a very 'lumpy' installation.
Using a copper wire (coat hanger, stripped Romex, etc.) Dr. Bailes illustrates how to check the quality of a spray foam job. multiple pokes reveal a one-inch thickness in one spot and a two-inch thickness right next to it.
Even the thicker of those spot-checks is only about R-13 or R-14— "not anywhere near the R-20, 21, or 22, which is what it should be in a vaulted ceiling" says Bailes.
Further, inspection shows some plywood wood roof deck visible, and a lump of nine-inch thick foam. These lumps do not average out into a good job, they add up to a bad one.
The Takeaway: Make sure to specify to your installer how thick you want the foam, and then check it for uniformity.