Replies

1. 
   DanH | Nov 10, 2015 08:50pm | #1

   Probably not needed, and might be ill-advised.

2. 
   mark122 | Nov 11, 2015 07:16am | #2

   No, vapor barrier is not needed/required.

   how come you cant run by this by a code official? on an addition that size i hope its getting inspected.

3. 
   Norman | Nov 11, 2015 10:36am | #3

   I thought it would go on the outside?

   My understanding is that for that sort of climate, you want a VB on the exterior side of the insulation for humidity control.

   OTOH, I am but an alledgedly humble DIYer, so caveat emptor.

   Good luck.

4. 
   user-621591 | Nov 12, 2015 06:17pm | #4

   Thanks to all for your responses.  I've decided to go with no vapor barrier.  Thanks!

5. 
   DanH | Nov 12, 2015 06:36pm | #5

   The one thing that an inside "wrap" would do for you is to provide additional air sealing.  With a batt insulation such as fiberglass or Roxul it's important that airflow through the material be minimized, as air movement greatly reduces insulation efficiency.  The housewrap on the outside solves part of the problem, but you also need to be sure that airflow is minimized on the inside. 

   Generally, simply covering with drywall accomplishes this, but one needs to develop a sort of sixth sense to recognize situations where airflow isn't adequately blocked and fix them.  This is around pipe penetrations and the like, of course, but also may be "odd" junctions in the framing where an air pocket is created which allows airflow through the insulation, beyond what's normally contstained within a single stud bay.

   Some thought is required.

1. 
   mark122 | Nov 12, 2015 08:37pm | #6

   vapor barrier on the interior of the building in an area like n. alabama would be a big mistake. in the summer time it would cause condesation because of the humidity and A/C.

6. 
   user-621591 | Nov 15, 2015 04:01pm | #7

   Thanks for the additional information.  I'm trying to be extra vigilant in making sure I find and close all possible sites for air leakage.  The only thing I can't figure out an easy way to do is where the interior wall is perpendicular to and meets the exterior wall.  That, along with the corners of the exterior walls which seem to be just hollow spaces.  Is it acceptable to cover these gaps with a vapor barrier?  What is the best way to cover or fill this? 

   
1. 
   DanH | Nov 15, 2015 04:24pm | #8

   It would be better to cover the gaps with Tyvek.

2. 
   finefinish | Nov 15, 2015 08:32pm | #9

   Hi there, I would seriously consider pulling out a stud at each corner and getting insulation in those corners.  That was a major oversight by the framer to either 1) build a corner detail that doesn't allow for insulation after he is done, or 2) insulate the pocket himself before attaching the adjoining wall.  This is new construction correct?  This is not acceptable unless you live somewhere the temperature is a constant 65 degrees.  Short of pulling studs out, I would tape/and/or caulk these joints as a last resort.  

3. 
   john7g | Nov 15, 2015 09:32pm | #11

   Foam

   At this point in your project, I'd drill holes every foot or so and fill the void in the foam.  There are easy ways to address this during the framing stage but now it's easiest to fill it with foam.  

7. 
   john7g | Nov 15, 2015 09:29pm | #10

   No, we dry to the inside down here and your barrier needs to be under the siding where it is.  Any additional layers will trap moisture.  

   I'm southwest of ATL.  

8. 
   user-621591 | Nov 15, 2015 11:44pm | #12

   Yes, the framer was negligent in overlooking this important piece and I have to say that's the only thing I've found fault with.  But now that it's done, I have to fix it.  If I go the way of drilling holes and filling with spray foam, (excuse my lack of knowledge here) should I fill it all at once or in layers while letting each layer expand before adding the next one?  Will it just expand upwards?  I don't want to overfill.  Thanks for the input.