"Jeff Thies" wrote in message
...
On 12/10/2010 8:06 AM, jamesgangnc wrote:
On Dec 9, 6:20 pm, wrote:
On 12/9/2010 3:07 AM, wrote:





On Wed, 8 Dec 2010 14:02:12 -0500, "Ed
wrote:

wrote in message
...
I've been working on my garage project and I'm about to the point of
installing insulation on the garage ceiling. The joists between the
living space above and the garage are 22" inches tall and
manufactured
from 2x4's. Inside them is the plumbing, electrical and most of the
hvac flex ducts for the room above. I also plan on insulating the
garage walls. I have insulated garage doors on the front and back
but
the front one is big, 20x9. The subfloor above is tongued osb.

Does it really matter which way I put the facing on the insulation
between the garage ceiling and the floor above? I know the vapor
barrier is supposed to be against the floor but i's going to be a
whole lot easier to install it with the paper on the garage side as
that will let me staple the paper to the bottom of the joists.
Otherwise I have to figure a way to hold the insulation up while I
install wallboard on the ceiling.

Easier is not always better, or even acceptable. Vapor barrier to the
heated side or potential problems Thee are metal supports made for
holding
insulation in place between joists. .

Better applications is to have someone come in and do spray foam.

What Ed said.

Ken in Calgary

Or just use foam board attached to the bottom of the joists. Don't
forget, if you have living space above, you need 5/8 firestop rock or
similar fire-rated material as a fire break.

--
aem sends...- Hide quoted text -

- Show quoted text -

Holding the insulation up while attaching foam board presents the same
problem as holding it up while installing wallboard.

I'm thinking maybe I'll use string and staple the string across the
joists after I put a batt up. Not any different amount of work from
stapling the batt paper. If I cut a couple dozen pieces of string the
width of the space I can just let them hang as I install batts and
staple the string to the next joist.


Use fence wire. String is hard to staple and have it hold. See my other
post.

I have used fiberglass tape, self adhesive and about 1/2" wide. Use a
stapler to attach to the joist, don't rely on the tape except to hold it in
place until you can fire a staple into it. Strong, flexible and easy to use.

Putting insulation bats between truss joists made from 2x4s will leave lots
of spaces within the truss joists allowing cold air to penetrate and will
still provide no vapor barrier at the floor level to prevent water vapor
condensing on the cold side of the drywall. It is still better to pay the
cost and have spray foam installed on the underside of the floor, it will
insulate and provide the vapor barrier without interference with duct
anchors and other obstructions. The ducts can also be encapsulated to keep
heat and/or cool from being lost. One could add some bat insulation
afterwards to boost the insulation value if wanted.