in my garage conversion, i'm laying insulation on the unused attic
floor; ie, right on the flat plywood flooring, not in b/ joists. i
can't get insulation blanket around here in r30, so i'm limited to 15"
and 24" width batts x 48" long. the cost of 15" suits my total-sq-foot
needs better, so i'd like to get it; but will more seam connections
with 15" result in less insulating power?

also: around here, neither lowes nor HD stock r13 in the 24" width.
they don't stock it and say they can't get it. i thought 24" was as
standard a width as 15". Is that not so?

thanks

ps: cross posted this to one other logical ng.

I was looking into insulating the ceiling in my pole barn shop. The
purchase price for the insulation from the local Ace Hardware store was
about $600. I called an insulating company, and got a price of $650 for
insulation installed with a white reflective sheeting over the
insulation.
robo hippy

Around here (central Alberta, Canada), the 24" insulation is about as common
as the 16". Don't know about other places, though. Even though the 16"
wide insulation is less per square foot, I went with the 24" wide for the
ceiling, as I was putting up vapor barrier at the same time, and I didn't
figure the two pieces would stay up there long enough for me to tack up the
plastic. In your case, with a finished floor, I don't think it would really
matter, but I'd look at renting an insulation blower, and buying the loose
fill stuff.

--
Clint
"flipper" wrote in message
oups.com...
in my garage conversion, i'm laying insulation on the unused attic
floor; ie, right on the flat plywood flooring, not in b/ joists. i
can't get insulation blanket around here in r30, so i'm limited to 15"
and 24" width batts x 48" long. the cost of 15" suits my total-sq-foot
needs better, so i'd like to get it; but will more seam connections
with 15" result in less insulating power?

also: around here, neither lowes nor HD stock r13 in the 24" width.
they don't stock it and say they can't get it. i thought 24" was as
standard a width as 15". Is that not so?

thanks

ps: cross posted this to one other logical ng.

Check the building codes for your area. The 24" is generally not
available if the local code does not allow 24" framing.

The joints are not a problem if you can keep the bats firmly pressed
against each other.

I would consider throwing a piece of something like tyvek over it to
keep dust out of the insulation and to provide another air barrier.

wrote:

Check the building codes for your area. The 24" is generally not
available if the local code does not allow 24" framing.

The joints are not a problem if you can keep the bats firmly pressed
against each other.

I would consider throwing a piece of something like tyvek over it to
keep dust out of the insulation and to provide another air barrier.



++++++++++++

Interesting I guess I never thought of laying tyvek over the top
of the pink stuff. Seems like it could trap moisture? Does dust
hurt the insulation? Why doesn’t any of the insulation
manufactures suggest doing this? I have a half a roll of Lowes
house barrier leftover, maybe I’ll unroll it in my attic…

TP

According to flipper :
in my garage conversion, i'm laying insulation on the unused attic
floor; ie, right on the flat plywood flooring, not in b/ joists. i
can't get insulation blanket around here in r30, so i'm limited to 15"
and 24" width batts x 48" long. the cost of 15" suits my total-sq-foot
needs better, so i'd like to get it; but will more seam connections
with 15" result in less insulating power?

If you're doing unfaced batts, the seams are irrelevant if you've
installed it properly.

also: around here, neither lowes nor HD stock r13 in the 24" width.
they don't stock it and say they can't get it. i thought 24" was as
standard a width as 15". Is that not so?

R13 is for 2x4 stud walls, and R20 is for 2x6 walls. Building codes
generally do not permit the use of 2x4s on 24" centers, hence, 24"
R13 is a pretty rare size.

You need to base your insulation selection on desired R-value, not
batt width. With unfaced batts, the determining factor in cost
per square foot is R value (thickness) not batt width.

There's probably a reason that insulation manufacturers don't suggest
using building wrap on top of ceiling insulation - it's a bad idea.
Dust in the insulation will not make much of a difference, and you
want to minimize as much as possible any blockage of moisture transfer
_out_ of the insulation.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.