Insulation, Radiant and Vapor Barriers - Ahhh, vapor barrier

So I have put vapor barrier up on the cinder block side of my stud walls. I have staped it to the tops of the wall frames instead of trying to reach the sill plate (if that is the correct term for the pressure treated 2x6 that rests on top of the cinder block wall. I will be putting R-13 batts of insulation inside the wall sections and covering the roomside of the studs with another sheed of 4-mil plastic.

There two sections where the stud walls deviate from the cinder block walls - to go around obstructions (a water heater and a HVAC unit. For these, I will be putting the drywall on the studs and then going back in behind them to put in insulation - with the paper side of the insulation to the non-drywall side of the wall.

Good?

You want the paper on the "warm in the winter" side of the wall. That'll place it right up against the sheetrock. The other way, moist air will travel into the insulation and get trapped there by the paper barrier.

Paper to the room side for sure. If this is a gas furnace and water heater they do get make up air I hope? Dont forget the R-19 in all the joist space up there on that sill plate all around the home.


ED;)

If I understand you correctly, you've installed a plastic vapor barrier against the masonry basement wall and will install another on the room side of the insulation. Contrary to the other posts, you should NOT install insulation with a vapor barrier if you're going to install plastic as you've stated. Double vapor barriers MUST be avoided. You should use unfaced batts.

P.S. (It's concrete block or CMU's - concrete masonry units, not cinder block. Cinder block is a lightweight NON-STRUCTURAL material used for interior partitions.)

You may not want to do this - take a look at

http://www.buildingscience.com/resources/foundations/basement_insulation_systems.pdf

Have been back in homes 25 years and more that we have did. Poly on the basement wall 2 X4 stud R13 paper back to the room poly over it drywall and some paneling over it . No mole, some have even been earth contact homes. Have always put a poly over paper back insulation in the home for a good V/B . Its to a point that some of the homes are getting knocked down now for the land. No mold in any of the outside walls with the poly over the paper back insulation. We do put drain tile outside the footing also a drain tile on the inside of the footing under the slab around the whole basement.

ED ;)

It's pretty obvious that the above link doesn't in the least apply to this situation (www.buildingscience...yadda-yadda). The link applies to situations where moisture is allowed to come through the foundation wall unimpeded, collect in the wall cavity, and cause mold. This is not the case here. The writer of the original post indicated that a layer of plastic had been placed against the basement wall. When applied properly and well sealed, this should eliminate the source of moisture in the wall. I think the given here is that the basement wall must be dry.

The above-referenced web page seems to recommend exterior insulation as the cure-all for this problem. If you apply exterior insulation to an equally "leaky" basement wall you will have the same problem you have with interior insulation - that is, moisture getting into the living space. The writers of the article are correct in their contention that an externally insulated "non-leaky" wall is better than an internally insulated "leaky" wall... (well duh!!) In summary - "leaks bad, no leaks good."

I don't know how it works in Florida, but architects, code officials, builders, and INSULATION MANUFACTURERS are becoming aware of the serious problems caused by double vapor barriers. (It only takes a few lawsuits to get their attention!) If you send design or shop drawings to an insulation manufacturer showing a double vapor-barrier they will respond with a VERY nasty letter and REVOKE all warranties. It is a bad and expensive detail. (Why pay for an additional vapor barrier that might result in a component failure and lawsuit??)