Insulation, vapor barrier questions

Started by Jeff922, June 30, 2011, 07:11:40 AM

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Jeff922

Right now I'm working on my electric.  It's slow going but actually quite enjoyable.  While working on this I have some time to think about how I want to do my insulation/vapor barrier/drywall. Plenty of time for an obsessive guy like me to thoroughly over-think everything.  The "analysis paralysis" is starting to set in.  A few years ago when I was going to my local community college working on my CADD degree, I took a class on residential building construction.  I remember that my teacher said that he insulated all of his homes with unfaced insulation and then covered it with poly (4 mil?).  He said that he used to cover the ceilings with poly but found out that it made things "too tight" and the houses needed to "breath" more.  What are your thoughts on this?  My gut tells me to cover everything with poly.  A downside to the poly vapor barrier is that it will cover the stud edges so I won't be able to glue my drywall, but I'm thinking since my place has had a couple of years to dry out that there won't be much wood movement.  And I can use more screws too.  What do ya think?  I'm putting insulation in some of my interior partitions for sound control and I'm assuming no VB is needed.  I know not to use a VB behind my damp-rated drywall, but is there anything else I need to think of?  Sorry so long winded.  Thanks for the help!
"They don't grow trees so close together that you can't ski between them"

Alan Gage

Have you read up at buildingscience.com? Lots of good info. there on the subject.

Alan


Danfish

Codes tend to favor the vapor barrier as a requirement in colder climates where cold exterior and warm moist interior lead to condensation in wall cavity.  Is you attic space vented?  If so, then ceiling barrier would be a good choice as there are many examples of frost build up on underside of roof sheathing...resulting in mold production.  Tight house issue is why continous running whole-building fan systems are now a requirement in California.  Also, you mentioned your studs have been up for a while...suggest you get out the shims and power plane to true up everything before you insulate and install the barrier.