I guess that would be one way to go but what about acoustic tiles? I think they're insulating as well, or you could run insulation between the trusses and then add acoustic tiles.

Ok, skip the acoustic tile idea! But honestly, I don't think spray foam insulation will work either. Hopefully someone here will have a great idea for you.

What kind of paint? You wouldn't happen to have a picture of how it looks, would you?

Not sure what kind of paint. The last place we noticed spray foam painted at restaurant ceiling (black) was at Pawleys Raw Bar in Pawleys Island, SC tel: 843-979-2722

I wonder if something like this could work for you. You could just layer sheets of insulation between the beams, then put this on top: http://www.armstrong.com/residential-ceilings/products/ceilings/cover-popcorn-ceiling/_/N-1z141rfZ1z141r9?cid=social_Facebook_FixUgly_ThisOldHouse

Thanks, I wasn't aware of these products.

Just curious - what did you decide?

Exposed spray foam is not allowed by code - it burns and/or produces nasty black smoke when exposed to fire. Foam has to be covered by an approved "thermal barrier", usually gypsum board, but wood has been used. Latex paint is not a thermal barrier.

you can use a special fire resistant paint, it's what the restaurants and bars use