I am about to drywall and insulate my detached garage ceiling. Instead
of stapling the kraft faced pink fiberglass insulation to the ceiling
joists, I was thinking I could save a step by sheetrocking the ceiling
first and then dropping in the insulation (paper side down) and save
myself the stapling. Will I have a vapor barrier issue, or is this a
this is way more work..... not to mention trying to manuver in the
attic space and not putting a foot or leg through the celing.. Another
alternative to think of is blown in insulation the COCOON brand
(recycled paper treated) is way less exspensive than bats and you can
do it yourself with a rental unit.
I just did the very same job in my garage a few months ago with R-38 batts.
You want to insulate first and then put up the sheetrock.
MUCH easier and more precise than trying to maneuver in the in the attic and
do it afterward.
This is a bit off topic to your question, but since you mentioned vapor
barriers, I figured it an appropriate thread to inject a comment.
Is the garage going to be a "conditioned space" and have moisture
sources? Will you be using the attic for storage or will it be totally
isolated from the downstairs? Do you live in a hot moist environment or
a cooler one?
A vapor barrier in a garage doesn't make any sense to me. Typically, a
vapor barrier is to prevent moist air from getting into a cold space,
condensing on the cold surfaces, and leading to moisture issues.
In a garage, there's not much of an air envelope so the inside air
would appear to be no different than outside. Perhaps with the doors
all closed, the garage will experience less temperature and humidity
swings than the outside, but overall, it's very different from a house
that is filled with moisture sources that will drive humidity through
That said, I've not seen many garages that have air sealing between the
attic space and the main garage. Hence a vapor barrier on your ceiling
will do nothing since the humidity throughout the garage would be
If I were in your shoes (and I sort of am because I'm just about to
build a detached garage), and I wanted to use the attic space for
storage (which I do), I would put a perforated radiant barrier directly
under the roof deck then insulate the upper cavities so that the outer
shell of the garage is insulated.
It sounds like you're further ahead on the project however. In that
situation, I'd still use a radiant barrier under the roof, then blow
cellulose into the attic space and avoid the pink stuff altogether.
Don't be talked out of a vapor barrier. I finished my attached
somewhat oversized two car garage with sheetrock after I insulated
the ceiling and walls several years ago then I put in a gas
heater, vented of course, to keep things from freezing with it
staying around 40 in the winter. Just last month, I put in a
washer dryer combo so I don't have to walk down to the basement so
often. So as to not have to vent it where I didn't want to, I got
an electric dryer and it vents into the garage. It gets rather
humid now and I'm glad I did it right years ago.
You might get slow yourself going down to the basement and do the
same thing in years down the road. Cover your butt now. :)
He would not need a vapor retarder if the space is not heated. There's a
huge amount of infiltration around the overhead door, and any moisture
buildup would dissipate in that manor (path of least resistance.)
If it were me, I would insulate with unfaced batts (support with plastic
strapping until the drywall is installed.
We frequently insulate after hanging the board however we use continuous
poly vapor barrier and unfaced insulation almost 100% of the time. The
remainder is blown with continuous poly vapor. The end result is a job
10 times that of a paper faced job.
If you do go with insulating after you hang the ceiling just install a
continuous poly vapor barrier, hang the ceiling, then either drop in
unfaced attic batts from above or use blown. Dropping the faced batts in
from the top will leave large leaks in the vapor barrier. This could
become an issue in the event the space is ever heated which is I am sure
why you are insulating in the first place.
Considering the almost negligible cost of poly and labor, why would anyone
NOT bother to install a poly vapor barrier before installing the drywall?
The fact the it will help to hold the (probably cheaper, I have not seen
faced fiberglass for many years) unfaced fiberglass bats in place is just a
Most of us seem to have pink and poly in the garage for years before we get
around to putting up the drywall. It often seems to take several more years
to get the taping and mudding done.
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