Insulation, Radiant and Vapor Barriers - Who is right?!

Ok, here's the scenario. I hired a contractor to build a 15' dormer and replace my roof. He did all the framing and what not, the roof, and the electrical. However, to save money, I did all the insulation. He told me what to get and specifically how to do it.

I put R-19 with a vapor barrier in the ceiling/roof. He said to get it with NO vapor barrier, but HD only had it with. He told me that was ok. He then told me to put 6mil sheet plastic over ALL the exterior insulation and that would be the proper vapor barrier.

So, the inspector just came by. He DID pass the work, but he said that the ceiling/roof should have R-30, not R-19. My contractor has since countered with, "It's actually a cost issue. If a customer only wants R-19, then R-19 is ok." The inspector also said that the double vapor barrier (the paper on the insulation itself and the sheet plastic) was actually bad and he told me to rip the sheet plastic off.

IF the inspector is right, fine. But I WILL yell at the contractor for having me do a lot of unnecessary work (the sheet plastic). Also, who's right about the R-19 vs. R-30 issue? If it IS supposed to be R-30, I will kill my contractor for giving me wrong info. If I lose money on energy because he is wrong, he's a dead man.

So, bottom line: Who's right?

Thanks,

Chris

DOE testing site recommends R-30 if you are renovating and R-49 for new construction. There should be one vapor barrier, on the side towards the living space. Two will tend to trap moisture.

It is a cost issue. Poor insulation will waste a lot of money over the years. The incremental cost of more insulation at the time of installation is a trivial matter overall.

I will be upgrading the insulation in my attic this week. It has R-19, not nearly enough. I can add R-19 bringing it to R-38 for $497 or add R-30 bringing it to R-49 for $810. Seems like an easy choice.

Here is the site:

http://www.ornl.gov/sci/roofs+walls/insulation/ins_05.html

Hope this helps.

So my contractor is wrong then. Time for him to die.

Thanks,

Chris

Your contractor should die

Id shoot them both I think. We put a 4 mil poly on ceiling rafters then the drywall with a blow in top there for R-40+. On all walls R-13 paper back to the room. Tacked inside the studs so no bumps in the drywall or panel. Then a 4 mil poly over the whole wall as one sheet this seal's it as no leaks anywhere air or vapor. Have been back in homes and have seen nothing wrong at all. Over many years.

my .02 cents

ED ;)

Agreed Ed, I put 4 or 6 mil over everything...period....no air leakage.

Wow,

Diggin' up an older thread, I see. Well, just to let ya'll know, the contractor bought the chewing out of a lifetime.

After having an amazingly fun time ripping him a new orifice (this wasn't the only annoyance), I ended up getting a pretty decent amount of cash back.

It's all good. :D

Chris