What part of SC are you in? My understanding is that you should use kraft-faced insulation in the exterior walls. Have you talked with more than one contractor?

I wouldn't worry about kraft facing. It is best to use unfaced batts and then add a polyethylene vapor retarder if required in your climate. You are in a middle zone so it might be a tough call. It will probably be determined by the exterior wall cladding, thickness of insulation, humidity, and HVAC system. This is a whole wall design issue rather than an insulation installation technique issue.

Tom, I always thought so too, but we have a good friend who is a dry wall installer and he says most of the homes he does have unfaced batts in them with no vapor barrier. So I am confused.

Mightyanvil, the exterior walls are 2x6 with OSB sheathing, house wrap and vinyl siding. The ceilings are vaulted in most of the house. the HVAC is a little undersized, but we will suppliment with wood heat. Hopefully the AC will be enough...it was a gas pac we already had so we are using it. The northern exposure of the house has an attached sunroom that runs almost the entire length of the house, so we will be a lot of protection from the north winds. Humidity here...well, it is pretty high in the summer but not like the gulf coast or anywhere like that. so....give that info, what do you think? I do trust this insulator...he has been doing this for a long, long time in this area.

You don't want an interior vapor barrier in SC. It's not quite the gulf, but we still dry to the inside. If you sandwich your insulation between two vapor barriers you are asking for trouble down the road.

Just based on the little I know about the wall and the climate I would say no vapor retarder on the inside if the AC will dehumidify the house during the summer. The wall would dry to the interior in the summer and hopefully it will not be cold enough for moisture to condense on the back side of the sheathing in the winter. If in doubt, an inch of extruded polystyrene insulation on the exterior face of the sheathing would be a good idea.

Here is a link that might be useful: Designs that Work from Building Science corp.

Two questions come to mind that I might ask the insulation contractor.

Is he concerned about settling?
Has any of his customers had their homes Energy Star rated?

When our home was being inspected, the technician pointed his thermal imaging tool at the top of the wall and commented on how you can see a temperature difference in a lot of homes due to settling. When our insulation contractor was on site doing the work, he had mentioned how he makes his guys staple the top. A 2x6 wall without faced insulation stapled at the top seems like a mistake to me, but I'm not a professional.

Here in the desert on many remodels, even kraft faced batts stapled well settled largely due to the kraft paper itself getting brittle and letting go at the staples. This could be strickly a desert thing as the dry air is hard on a number of materials that might not be the case in other areas, but i've seen gaps as much as 4" or so from the top plates to the upper end of the batts due to settling. For unfaced insulation, using wire similar to what is used for underfloor batts to keep them in place might be a good idea, only wire up at the top end of the insulation to keep it from dropping down.

Thanks for the input. I'll ask the insulator how he intends to keep the batts from settling. I had not thought of that potential problem.

Properly fitted friction fit insulation shouldnt settle.

I have seen beautiful kraft paper installations, but the insulation behind the paper was still crappy install.

I despise kraft faced insulation.

If you use a friction fit batt, make sure that the entire batt is pushed all the way to the exterior sheathing to begin with, then it is fluffed/pulled back out from the front face till it fills the cavity completely, or is slightly proud of the stud face.
When instaled this way, you get the maximun efficiency out of the batt, and you get slight compression of the batt, when the drywall is applied.

Its not rocket science, but its not as simple as just stuffing the product into the stud cavity either.

Forgive my ignorance....What is "friction fit insulation"?

What insulation should be used in the humid gulf south?

What insulation is the least likely to fuel a fire?

Originally insulation bats used the extensions of the backing to allow it to be stapled in place. That's pretty much gone around here. Most vertical cavities are filled by using insulation that is slightly wider than the cavity which allows it to be wedged in place. When insulating crawls or other horizontal unsupported you have to put something in to hold it.

None of the popular insulations will "fuel" a fire. Most will be destroyed by fire. Some very limitted ones may provide some amount of fire protection/blocking.

Thanks Ronnatalie