[Phantom]

Why I mentioned neoprene was for its flexibility, durability, resistance to crushing/crumbling, more resistant to fire, can easily be adapted for vent holes, helps with vibrations, and can wrap the whole battery.

I under stand the semi-permeability of neoprene and that can be easily fixed by adding something like fiberglass resin, super glue, contact cement, ect. I have never worn a suit on polystyrene but put a wetsuit on even on a 70 degree breezy day and you will be burning up in no time.

If you are adding a heater any way what will warm the battery more the heater sealed away from the engine heat in polystyrene? Or the heater and allowing the engine heat soak in? I guess it could be tested in an oven with the materials and two thermometers.