There are two types of spray foams. Closed-cell and open-cell. Let's talk about the difference between open-cell insulation and closed-cell insulation.
The very first difference between the open cell and closed cell is that open-cell has an R-value of 3.6 per inch whereas, the closed-cell has an R-value of 6 per inch. So that's one of the obvious reasons between one and the other, you will get a higher R-value with the closed-cell than the open cell.
The second difference you will notice is when you touch it or feel it the closed cell insulation is very rigid. It's quite hard and if you try poking through it with your finger it won't be possible. Now if you take the open cell insulator, you'll notice it's quite soft, you can bend it and break it, you can poke through it, etc.
Now let's talk about applications. The open cell insulation is something you'd like in your attic if you're looking for just insulating the attic better. Closed-cell insulation is preferred in places that experience severe weather conditions, for example, a place like Florida that's known for hurricanes. People staying here usually prefer to get their roofs coated with closed-cell insulation as it also kind of super glues the roof together.
But a big difference between one and the other is, the open cell if looked under a microscope would appear to look kind of like a sponge. It's porous so if one were to pour water on the top, it will seep to the bottom in a while but that's not the case with the closed-cell as it will not let water get through it so you could say it's quite water-resistant. And there's also a pricing difference between the two, but then again these are just a few qualities of glass wool roof insulation material.