Applicators tell me it doesn't matter. But I prefer to have it sprayed on before the framing so there's no impediments to an even application.

However, the home shouldn't be occupied till all obvious gas fumes have dissipated.

The spray doesn't provide better results than foam board but is faster. However, it's a lot more expensive than if you diy with foamboard or can find capable labour to do it. And there's always the lingering doubt over safety.

Here is a link that might be useful: Spray Foam Insulation: Poisonous Fumes?

This post was edited by worthy on Mon, Jun 10, 13 at 19:10

+1

Consider rigid board. Less off-gassing, cheaper, etc.