Bottles as insulation-do they really work?

Filling shed walls is in my near future.
I have one green house and potentially two sheds that will need to have their walls filled in.
If bottles are actually insulative, I can save a lot of labor, plus they are quite inert in this usage.
Tamped earth is my default infill, so anything that is more insulative and less work will be better.

From what I've seen, bottles by themselves have very little insulating value. They will provide a thermal break IF they are surrounded by a decent amount of actual insulation. That implies a fairly thick wall -- not sure if that works for you.

Thanks for your reply!
My walls won't be very thick at all, so the bottles may not work well for me.
Ah well, I have plenty of other things to try.