My insulation theory, take a look.

agesilaus wrote:
You can buy poly foam in a large container, about like a small propane cylinder. And use that to fill your walls ect. It's designed as insulation which this other material doesn't seem to be. Or you can pay a contractor to do it.

Polyurethane is polyurethane, it's the same thing.
The only difference is that it's poured instead of being sprayed, and that's not my opinion, it's a fact.

anyways look at this picture, you can't just put the nozzle in some of the holes or shoot it at the bottom and hope it will fill the void.

I had the upper walls and ceiling done by an insulating company and they didn't want to do the bottom part.