lol dry ice is 20cents a pound. about as expensive as mylar.
i used to work for cardinal glass, as a lami cutter, and glass handler, he's right the low-e coating you can simply screw up with a finger smudge. on the other hand, look into the low-e2 smart glass, i think u might have something there.
what about pumping it via ducting to the hood and have a flow through ventilation, doing it that way you give enough time/space to let the cooler air warm up a bit, i know my grow room is about 10degree's higher than outside in the summer, depending. now only tempered glass would break from that kind of heat/cold, regular glass expands and contracts. i have not done this, but its a theory, besides, even with flow through venting, alot of the heat is sucked right up and out the door.
just a suspicion, albeit i wouldnt chance the fire hazard, although i do brew wine in my grow room(turbo yeast).
edit: the gas ur talkin about is argon. and the low-e coating will do exactly that, it will absorb alot of energy, thats what its designed for. i.e leaving the argon(the heavier substance) is supposed to curb whats left, i.e content of argon. aye, and for u to get ahold of a piece of low-e glass, raw is going to be expensive.