On Nov 29, 1:15*am, "todd" wrote:
OK, I've put this job off all year while it was warm. *I need to insulate
the garage/shop attic. *I have about 500 SF of attic space to insulate and
the joists are 2x12 on 16" centers. *I'm trying to decide between cellulose
and fiberglass. *From what I can determine, cellulose will be cheaper to
install and may perform better. *In fiberglass' corner are built-in vapor
barrier and maybe easier to deal with overall. *Here are the questions I
have.

1. *The manufacturer's instructions for cellulose only state the blowing
machine as a method of installation, but a few places on the net that I've
read state that if the rafters are exposed, you can just cut open the bags
and essentially dump the stuff in. *Can anyone confirm one way or the other?
2. *If I use cellulose, do I need to put down a plastic vapor barrier first?

Anything I'm missing?

TIA,

todd

Todd,
It is common to break up cellulose insulation by hand and rake it into
place for very small areas around repairs. Perhaps a brick or two.
Like the other posts have mentioned it is not realistic for an entire
job and the end result will not have the loft and coverage like if you
use the machine. There will be large chunks and voids which is not
what you want. Additionally with the machine you can really minimize
your effort by being able to shoot it all the way out into corners
meaning you can hit large areas by standing in one spot.

With regards to the vapor barrier, it has been a highly debated
subject in the building industry but mainly with regards to spaces
that are conditioned in summer. I personally feel it is necessary
however depending on your situation it may be very difficult to
install. Typically if cellulose is to be used, prior to installing the
interior ceiling material you would tack up a poly vapor barrier. If
this wasnt done the only option would be to attempt to install it from
the attic which would likely be a nightmare and could pose some other
problems.

If your finished ceiling in the space is well sealed and painted, and
your attic is well ventilated you may opt to forgo the VB but you have
to remember that cellulose can hold a tremendous amount of moisture. A
few key things to remember are #1 Respirator, #2 a fan pulling from
the attic is handy to clear the air while your blowing, #3 Respirator,
#4 Dont block your air flow from the soffit vents into the attic (dont
pile insulation against the underside of the roof sheathing at the
outside wall), and #6 Respirator.

Here is a link you may find handy,
http://www.cellulose.org/userdocs/Te...Bulletin02.pdf
section 9.1.2 speaks to the VB

Mark