I'm doing lots of remodelling in my house and I'm considering opening
up the exterior walls and replacing the fiberglass insulation. Has the
R-value of 4" insulation improved since 1953? If not, I'll just leave
the walls alone.
Well, if it is indeed insulated with fiberglass, the 3 1/2" thickness has gone
from the old R11 to R13. But it is probably not fiberglass. Any house of that
vintage that I have had the walls out where they have been insulated, used
cellulose batts. In every case, they have disintegrated into dust. Do a little
exploration on one wall to see what you have. And there is a pretty good chance
it isn't insulated at all unless you have reason to believe otherwise.
Fiberglass is apx 3.75R per inch, foamboard goes from R 5 to R 7.2" but
it costs alot. It depends if your old insulation was done right, it may
be fine but even if done right total R value is not optimal.
: Fiberglass is apx 3.75R per inch, foamboard goes from R 5 to R
: it costs alot. It depends if your old insulation was done
right, it may
: be fine but even if done right total R value is not optimal.
I'm slightly confused.
For the equivalent R, yes, it's more expensive for sure, but
not by several magnitudes. I got a great theoretical R with a 3"
thick board in the 2 x 4 spaces, For about 2.5 times the cost of
a roll of foil faced 3.5" insulation and I got an R of supposedly
20, plus a little if the air gap's right. Using two layers of
1.5", interestingly enough, would have cost me more, plus lost a
couple of points in the R scale.
So ... teach me here if you can: How is the total R not
'optimal'? It's really NBD since it's "just" a porch, but the
walls are actually almost warm to the touch, compared to our
front porch, which feels cooler and has 5.5" 'glas in the 2 x 6
spaces. So, I'd ass-u-me-d it was an improvement. Both are
heated BTW, and make "day rooms" for me (I'm disabled) when I'm
having my "bad" days. I'm coming at it from a $ to heat cost, of
course. Oh, one's an east, the other a west exposure.
Or am I not understanding your comment?
: > I'm doing lots of remodelling in my house and I'm considering
: > up the exterior walls and replacing the fiberglass
insulation. Has the
: > R-value of 4" insulation improved since 1953? If not, I'll
: > the walls alone.
: > Mike
: Are there better materials than 1953,,,, Yes. They cost a lot
: fiberglass and cellulose.
I've really been impressed with the "blueboard" insulation
lately - per inch it's slightly better than fiberglass numbers
and worked wonders on my porches; it also works as a vapor
barrier. Cuts easy, but a little more work than 'glas, a little
more expensive too. I like no 'glas mess with all out pets
Assuming what is in there is still in good shape, that is it is still
filling the cavities, I don't think you are going to gain much of anything
by replacing it with fiberglass. Now if you want to replace it with a
foamed in place modern foam, installed by professionals, you could make some
noticeable gains, but it is going to be expensive.
I have the blueprints to the house and they call for 4" fiberglass
batts in the exterior walls.
How about the pink or blue styrofoam sheets? I Googled and found the
blue extruded stuff to be almost R-5 per inch. Three inches of and I'm
at R-15. Are there any calculations I can do to see if the increased
insulation energy savings will offset the cost of materials?
And since expanding foam was brought up....How come you can buy a small
can of it, but you can't get a larger quantity so that you can do
It's a proven fact that any size window or door will use just a little bit
out of the last can of foam. Sometimes it needs just a little bit from the
can you left at the store. It's a conspiracy. Actually, for those that don't
know, yellow stuff is packaged just big enough to lift a cast iron bathtub
exactly 1.83 feet off the floor before it cures, unless the walls and floor
are reinforced, and not made out of drywall, then it lifts it 2.47 feet.
That's for those that find low tubs hard to get in and out of. In a
government study, they found that a large number of expanding foam marketing
people used to work at the hot dog bun factory! No joke. 87 million dollars
was allocated to the project to find out what the connection is. An
anonymous contributor to the study was quoted as saying, "If we all stick
together, we can sell a BUNCH of steel cans, plastic straws, and
You can, fastenal and mcmaster have it, but it is still expensive.
Believe it or not it is cheaper to pay to have it installed, as long as
they do it right, which is not guaranteed.
If you are not averse to creating new extension jambs for the windows,
and doors, think about an inch of blue foam under the sheetrock or under
the siding. That would be your best value, since it insulates the
studs[which are only less than R 5 total]
If you are working on the outside, removing the siding, then that stuff
is good under the siding, but don't try using it to replace the fiberglass,
as it will not seal well around the edges and the air leaks around it will
cause more heat loss than you might be gaining.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.