It looks like I'm going to have to pull the old T1-11 off the south side of
the house due to delamination. While I'm torn down to the insulation is
there a material that would use the same space as the old fiberglass
insulation (1973 construction)? The southern exposure causes the room to
heat up badly in the summer. I'm thinking a closed cell foam or a spray on.
Or, isn't it worth it?
You have to do the numbers for your area to say whether it's worth it or not.
Closed cell foam does have slightly higher R values than open cell, but
eventally there will be a leak and open cell is purportedly better for passing
the water through when closed cell will hold it in the wall where it will cause
mold and rot.
Also - R value is not the primary consideration. You might also consider a
hybrid approach - better economics. Spray a small layer of foam for the sealing
properties and use unfaced fiberglass to fill the cavity.
sprayed closed cell foam is likely twice the R value as old
Foam R6 or R7...... plus it seals all the cracks etc.
you could fill the cavatiys with foam and add a layer of foam over the
entire wall too for even better efficency
thats pretty common when people reside here
Fiberglass is about R 3.75" spray on foams go from about R 5"-R-
7.2". Foamboarn from R5"-R7,2" and the 7.2" is foilfaced for the
additional benefit of a radiant barrier. It makes a big difference
using foam and spray on will seal all air infiltration, it is worth
it, but consider the R7.2 foilfaced and caulking the first and last
sheet to stop air infiltration.
OP could make that wall thicker by say foaming the cavaties then
adding foamboard for extra R7.
if wall is 2 by 4 he could take current old fiberglass 3 inch from
to a much cozier and better sealed R 28 plus the radiant barrier.
caution should be used!! he might like it so much he decides to
upgrade the entire house:)
there are heat loss calculators that can evaluate the energy savings
on the different insdulations
'Worth it' depends on where you live, cost of heating/cooling and how
much value you put on comfort.
Is there a chance you could add High-R sheathing before the T-111? I
would at least look into a highly reflective barrier. You mention
heat entrance as a major concern so the materials available to you are
likely different from those I'm familiar with. Here we battle to keep
heat in- not reflect it back out.
Have some local insulation contractors come out and make suggestions.
Thanks for the replies so far, everyone. Let me fill in some of the blanks
I left and some of the Q's that you have. This is a rancher with the
narrow, 28' wall, with a hip roof which face south. There are two 30"x42"
windows and a door (unused) on the wall. So, the hip roof is an issue with
heatign but I have 12" of insulation up there. The windows are 8 years old
and have a high 'E' coating (or is it low - I've forgotten) and argon gas
between the panels. I had also thought of foil faced foam board over what
ever I use for insulation but there is going to be an issue with covering
the corners since this side will protrude further than the original other
two adjacent walls. So, now I'm thinking, remove the old glass, spray in
foam, run a treated piece of lumber along the bottom to keep insects from
burrowing into the foam board, wrap with Tyvek, add the foil-faced foam
board and replace the T1-11.
Hey bob, you said, "OP could make that wall thicker by say foaming the
cavaties then, adding foamboard for extra R7. if wall is 2 by 4 he could
take current old fiberglass 3 inch from about R10 to a much cozier and
better sealed R 28 plus the radiant barrier." You're right about the 2 x 4
walls. How thick is the foam that you are considering that would take me
out to R 28? I had considered adding another 2 x 4 to the existing ones to
increase the cavity to 7" but that would kill any overhang and make the
place pretty ugly. I'm looking for the fine line between efficiency and
Steve, thanks for the wet cellulose reminder! We have a new guy in town
doing that. It would probably eliminate the Tyvek. Now, as for asking
contractors, I've been doing that for years and the pat answer is, "I'll do
what ya want".
Thanks - more ideas are welcome. I'm beginning to develope a plan thanks to
my point is that replacing the fiberglass, its likely just over R3 per
inch. with closed cell expanding foam R7 gains you about R4 per inch
so 3 inches is a R12 gain:)
or a total of R 21.
then add foam board with radiant barrier that adds about R7 per inch
so 2 inches is a R14 gain
so the combined effort would net about a R 35:) plus you gain the
locally most people residing are adding the foam board as part of job.
plus it covers the studs too for better insulation
so overall gain of
Wet sprayed in place cellulose is the best way to go. Will stop air
infiltration and it fits all irregular spaces around wiring, plumbing
etc. Even having it drilled and filled after the siding goes on will
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