Let's think about moisture movement. How will it get into walls? When talking about "vapor barriers" the typical culprit was thought to be vapor drive. We now know in reality it is airflow.
The problem arises when warm moist air comes in contact with sub-dew point surface temperatures. The more airflow, the greater the problem (if the surfaces remain cold).
One point of dense pack is to slow air flow through these cavities. Slow the supply of moisture and the building components may be able to naturally deal with it. I think you'll see this idea of "vapor barrier" going away because they too often are causing moisture problems, not preventing them.
In your climate where would you put the vapor barrier? Inside wall? What about cooling season! Outside wall? What about heating season! Both walls? Now you've really done it. Once moisture gets in it'll NEVER get out!
Here's a good article you might find helpful from one of the fathers of modern building science: http://www.buildingscience.com/documents/information-sheets/vapor-o...
Vapor retarder like Tyvek would be good, but a vapor barrier like plastic would be bad (slight hint)
I have taken apart a few jobs like that where there were actually no issues- i.e. no issues with bulk water intrusion & the paint acted like the barrier / retarder preventing the dreaded moisture transfer from the outside - in
Would I do a job like that here - nope, as I can't guarntee that the issue isn't there, nor will be in the future
Might you be ok, possibly, but I would lookat it on a case by case basis - as you would have to judge it based not only on the overall climate, but the climate & conditions around the house - trees, shrubs, sprinklers, water flowing towards the house, mossy areas, water splashing back at the house, etc... next to the wall would all be bad signs
A couple of things: you mention no "vapor barrier" between the studs and the siding. I'm just wondering if you actually are talking about the rain barrier, typically tar paper under the siding, which is the part of the assembly that is shedding the rain off the building. If indeed there is no tar paper under the siding, that is cause for concern, and is something I would normally have to have a serious talk with the owner/contractor about. Usually, I will recommend against retrofit dense pack in a house like this. Lots of problems are possible with no tarpaper rain barrier, although the mild climate here in the San Francisco Bay Area can cover up a multitude of sins. Vapor barriers are not required for the most part by building codes in this climate zone. Tahoe or Minnesota: that's a different story. As regards possible problems with dense packing walls, I think that one possible culprit, and this is all too common, is that the room(s) are inadequately heated, therefore not drying the wall assembly to the inside. Or walls that never get any heat gain year around. What was mentioned previously about air transport being the main transport vehicle for moisture has been pretty well established.
Overall, I've seen no problems with dense packing walls over my 20+ year insulation career in Marin County.
I've also done some dense pack in ceiling cavities with no adverse effects (knock on wood).
San Rafael, Ca
I bought my house in 1981 and filled the walls and ceiling with cellulose, and was concerned for years about the vapor barrior issue which flip-flopped a couple of times. Long story short, I'm glad that I refrained from using anything other than paint and polyurathane, as a moisture retardant on the interior finished surfaces. The exterior siding is over asphault paper, the rain sheild. I believe that any moisture migration in the cellulose gets an opportunity to dry out and, with my 30 years of adventures with my saws-all, have never seen any evidense of mold or anything else to be concerned about. Cellulose is exceptionally forgivable.
That's my coastal Maine experience, and it's been very good to me.