freezer burn is not caused by air in the package.
freezers have inherently very very low relative humidity.
as a result water - now frozen - is extracted from the frozen meat (for example) and sublimates thru the packaging into the freezer air.
the surface of the meat/vegetable/whatever dries out - and the affected areas have been labeled "burn."
many/most plastic are not especially good moisture vapor barriers.
some are better than others - co-extrusions typically.
in the zip bag arena - on the shelf you will see "storage bags" and "freezer bags" - storage bags are just low density polyethylene, the freezer bags a co-extrusion of low density and high density polyethylene - which is a better moisture barrier.
those silvery bags around electronics / etc? not only static 'proof' but they are metalized - molecular layer of metal deposited on plastic because . . . .
the two commonly available materials which are completely moisture proof (and oxygen proof...) are
metal
glass.
freezer burn is not caused by air in the package...
that's because given the space available, the moisture sublimes on the the surface of the meat/other instead of forming frost on the freezer wall.
in a frost free freezer/refrigerator - one never sees the frost on the wall....
if it is wrapped tight, there's no space "inside" the wrap for the frost to form /accumulate ....
Ross - what are the specs on the vacuum bags?
typically they are a co-extrustion - LD poly "inside" to do the heat seal, and a HD poly / polyester outer layer so the outside doesn't melt during the heat/seal cycle.
I did R&D working with MVTR materials, ultrasonic / RF sealing plastic tops on containers, etc. - so I do have some experience in the technology.
edit to add: I don't lose stuff to freezer burn in freezer zip locks - but primarily because I don't keep it for 1-2 years in the freezer....