Moisture vapor

Putting individual strips of vapor barrier in the stud bays doesn't accomplish much unless you seal the edges, which is labor intensive.

Get some tanks of spray-in urethane foam, and fill the stud bays with that. That will get you insulation, wind/vapor barrier, and wall-stiffening all at once. Do it in multiple passes, so you have less overfill to carve off.

use spray closed cell foam, pricey but excellent insulation, makes for draft free quiet home.....

this foam is sprayed in all the cavities. and trimmed for easy wall board install, self vapor barrier its about R6 per inch!

May have misread your question. But strongly suggest you read up building codes for wall/ceiling insulation and vapour barriers for your area etc. Also check attic ventilation which is also very important. In the cool-cold climate here, for example, the vapour barrier goes on the warm side of the insulation, carefully sealed, to prevent warm/ damp house ait r from getting out into the insulation; condensing there inside the wall and causing rot, mould and deteroiaration of the insualtion! Vapour barrier is impervious to moisture and prevent moisture through it. On the 'outside' of the wall (i.e. under whatever siding you have/ using you should use a permeable barrier building paper or house warp such as Tyvek. That is water resistant but allows the inevitable moisture within the wall to evaporate out and not cause problems.

Vapour barrier always goes on the warm side of the wall. In Louisiana I assume that your summers are much warmer than your winters, so you would want the vapour barrier on the outside side of the wall.

Without removing your siding your only real option is spray in foam. I've never used it but I'm told that it's pretty much the best stuff you can use anyhow. The only downside that I can see is that if you ever need to remove the siding later, it will have the foam stuck to it. Once you've sprayed the walls and it's dried you can install fiberglass to finish the job.

Also, Tyvek is NOT vapor barrier. It is designed to let vapour through, but stop drafts.

That's a pretty safe assumption... :)

Not wrt the polar regions of Louisiana.