Blow-in Insulation and Vapor Barrier Paper

[Humpy]

A well installed moisture barrier (home wrap) will help R value and block some of the draft. The spray foam insulation is a god send for old houses. Those drafty spots just need a bit of the foamy stuff.

Vapor barrier is a different animal. It's for fairly specific builds and can cause alot of problems if done badly. I've been told to avoid it in our location (northeast). Here is a bit of proof but certainly not exhaustive research http://nationalfiber.com/docs/CelluloseInsulationMoistureAndVaporBarriers0909.pdf

Essentially, a vapor barrier (plastic sheeting) isn't needed anywhere in the 48 states.