Kevin.....try this for me....
Take your unit...or any container really, and put it in the freezer.
The test could be like this, since it's difficult to control exact temperatures, this gives you a good idea. Take 2 containers exactly the same filled with exactly the same material. In your example, both distilled water, but one covered in insulation. Put it in the freezer, and check them ever _X_ amount of minutes. You can compare how the insulation works by how it looks compared to the normal water. For instance, it will definitely freeze later, but how much later? You will know in this way how much improved it will be. My guess is it will not fare that well. But I've not tried it.
Also, I am going to do this with a standard electrolyte solution of NaOH and water vs. water and see how much it lowers the freezing point (if at all).
Also, thrival, you may want to do that to test how much salt you may need in the solution.
I'll be trying this later on, when it's closer to the colder temps, as right now I am really busy working on my units and cars, etc
