Insulating the hull questions.

[ebb]

Kurt, we have talked about your pink foam idea befor, so excuse me please if I repeat stuff. Pink and blue foams are relatively stiff sheet POLYSTYRENE FOAM insulation usually found at the big box depots.
Small panels could be heated and softened and pushed into the compound curves of an A/C hull. The compound curves are essentially minor in small sections. Gorilla polyurethane glue though is fairly expensive. But probably a good choice considering hull heat and cold cycling.
I think the pink foam is gluable with anumber of mastics - I wonder if tube 'threshold cement' could be used? Or perhaps tube glazing caulks/sealants (not silicone) that are formulated more toward heat extremes than construction goops.
[later EDIT: one structural polyether tube goop, I can recommend, is Chemlink M-1, considered green, non-toxic, bonds almost everything.
But haven't used it for the purpose here myself. There may be a problem getting it to set if no air moisture can get to the glue under closed cell stuff. It may not matter becauwse it begins setting immediately. So after tooling it on both surfaces with a toothed plaastic spreader, the open time may have been enough of a catalyst to promote it becoming rubber. More elastic formula Chemlink Novolac might be better for this app.]

I agree that polystyrene should be encapsulated.
As you say to protect the boat's interior from the foam's outgassing when the hull is heated by the sun or the ship's stove.
The encapsulation might also be augmented with paints. A good one imco would be a waterborne rubber urethane. As in deck paint without the antiskid.
Or an acrylic latex exterior house paint.
The encapsulation is suspect too, even plywood has formaldhyde in the glue.
SO encapsulate with glass or ceramic!!

Polyethylene foams don't have the same outgassing problems that the Bisphenol A toxin group has.
Note that when this foam burns it doesn't produce lethal smoke - which can't be said for other foams.
Who knows for sure? To be safe ALL foam insulation in the enclosed interior of a boat should be encapsulated.
Ensolite is used for a host of consumer products, everything from kneepads to yoga mats, and Airex is the same stuff in expensive closed cell mattress form. Bad chemicals. Goodlord maybe warmed up gelcoat and epoxy paint will compromise my tired immune system.

Tim,
I'm old enough to believe that that most of my body's complaints is due to decades of direct exposure to chemicals/solvents I've used. I think most of my toxic episodes are cumulative. Once thought the liver and kidneys where born-again and repairable.
NOW I go nuts trying to find less lethal materials to use on the boat,
especially inside.
Can't work with a canister mask on - besides having a beard which screws up a mask's breathing seal.
That non-toxic floor adhesive is not bad stuff - altho finding it was a problem.
Waterborne glue takes longer to set up than solvent glues - especially when you're gluing on closed cell material! Might ask if it ever sets up in some places? You have to be able to hold it in place by putting props or pressure on the panels.

California has led the way in safer products. You can legislate the great corporate planet polluters into making more friendly products.
But never turn your back on those jerks. Remember WCField's first law of consumerism:
"Never give a sucker an even break - or smarten up a chump."