I am remodeling a small home built in 1945.  They exterior walls are 2x4.  They now have the old tar fiber style insulation combined with blown in cellulose.  My question is.  Am I better off stuffing the old cellulose back in behind the vapor barrier rather than going with plastic wrapped batts?

I am relatively new to this and the constant upgrading and introduction of new products. What is my best way to go?

Too many particulars to ponder, but in general, blown goods are going to outperform fiberglass batts for a variety of reasons (fewer gaps, no compressions, much lower convection currents within the insulation, etc.) If the interior & exterior wall sheathings are structurally sound, DENSE PACKING the old cellulose in combination with new goods would be an excellent option. By pumping it up to 3lbs + per cubic foot density it'll increase the R value of the existing goods by 10% or more (comparable to new cellulose), and reduce infiltration & convection by ~90%.

Are you sure there's an actual vapor barrier there, rather than an air-barrier facing (that is at least somewhat water-vapor permeable?) Is it on the interior or exterior, and in what climate zone/location is this house?

Thanks for the input Dana. I removed the old sheetrock to rewire and add more cable/phone jacks. I put poly on the interior side behind the rock. The exterior sheathing seems to be in great shape. We just had it resided a couple years ago. I also caulked around all the cookies where they blew in the cellulose. I live in central Minnesota. So I should remove the batts and dense pack the cellulose behind the poly? It won't take much to pull the rock back off the exterior walls. I have not started to mud and tape yet (my winter project). Thanks again for the tips and advice. J

Pulling it apart to dense pack is more likely create problems at this point. Hopefully your siding is back ventilated (vinyl, or with a rainscreen gap?), or the average humidity of in the cavity may go up, since poly would block any chance of drying toward the interior.

Also, to dense pack it you'd have to either leave the sheet rock up, or do a blown-in-netting approach.

Thank you for the information. They are really reliable for people who wishes to remodel their houses. They now have a guide and have knowledge on what to do whenever, wherever.