Code requirement for an ignition barrier may be satisfied by 1.5" of mineral fiber, 3/8" drywall or 1/4" wood structural panels; other ignition barriers, including spray or roll-on fire barriers, may be accepted.

See link below for picture matching your situation. Your SPF installer should have mentioned this requirement.

Here is a link that might be useful: Decoding Thermal and Ignition Barrier Requirements

Ignition and thermal barriers are different, but related concepts. Having one doesn't preclude the necessity of having the other.

Wow, that was FAST, Worthy! From the date on the powerpoint booklet, I guess this is timely. The drawings at the back of the booklet are very helpful (our situation is a vented attic). When I've had a chance to discuss with builder and inspector, I may be back on-forum.

Thanks so much for your help!

Hi mjlb,
We'd like to understand more about your attic insulation and the gypsum board suggestion. You are welcome to contact our Building Science team to discuss your unique situation and get to a solution, please call us on 1-800-758-7325 (tollfree). Look forward to hearing from you!

additional info.

http://sprayfoam.com/newsarchives/archivedetails.cfm?id=512

open or closed cell? you are aware that to achieve
R-38 will take several inches of foam?
open cell is about R-4 per inch closed cell about R-7.
code doesn't accept q or k values invented by foam
companies.

best of luck.

Thank you all! It never ceases to amaze me the info available on-line.

Geez - a forum devoted to thermal barrier and ignition barrier for sprayfoam - who'd a thunk-it?

I passed the icynene 800 tel number on to the builder, since he is more conversant with the details of this project.