Is there any reason NOT to place 2 inch thick rigid foam insulation
horizontally 2 feet wide, buried 12 inches deep, all around the
perimeter of my 7 foot cement block foundation?
3 feet of the foundation is above grade and will be covered with rigid
foam insulation to a depth of 1 foot below grade. This will then be
covered with some sort of protection like, say, stucco.
Any thoughts on this would be appreciated.
On Mon, 20 Jul 2009 09:16:59 -0700 (PDT), "Robert.Thompson"
If you use a closed cell foam insulation, you're OK. If you are using
an open cell foam - all you are really going to do is soak up moisture
and hold it next to the concrete block. (P.S. Concrete block not
cement block - Portland cement is a relatively small part of the
material it's made of - just a pet peeve of mine...)
Depending on where you live the practise of insulating from the
exterior can be done best by either extending the insulation down to
below the frost level or by going down either 2' or 4' and then out 4'
so that any heat transferred from the interior doesn't transfer to the
The stucco wire will need to be fastened to something - use a wood
nailer at the top and bottom. You want to use parging rather than
stucco at grade level.
I really dont understand what you are saying, do you want the 2"
laying flat not touching the foundation, if so it makes no sense, you
are not insulating anything. Your walls are 7ft right, but you plan on
only insulating 4 ft of it. What zone are you, what is freeze depth,
im zone 5, freeze to about 36" I put foamboard under the floor and
covered the whole foundation wall. If you are even in zone 7maybe 9,
id insulate it all.
I plan to insulate only 4 feet because I do not wish to dig down to
the footings and this is why I am asking about laying 2" foam board,
flat and butted to the wall insulation. This foam would be 2 feet wide
and run around the entire house. I could bury it about 1 foot deep.
On the inside, the top 4 feet is insulated with 1.5" foamboard glued
to the concrete block. The bottom 3 feet is insulated with 2" foam
board. The concrete floor "floats" on 2" foam board and butts up to
the 2" foam on the lower portion of the wall - no contact with the
My concern is if there will be any negative consequences to installing
a 2 foot 'wing' on insulation around the perimeter.
I live in Montreal, Quebec, Canada. Footings here must be at least 4
feet deep so I assume that the frost line is slightly above that.
Termites and other problem insects like to tunnel in foam. I don't
know how big of a problem termites are in your neck of the woods, but
you should investigate that aspect.
Here's a link to an EPS EIFs termite page to get you started:
Its not going to do any insulating unless its against the house,
foamboard goes from R 3- R 7' If you are using R5 the top is only
insulated to R7.5, thats not much in your area, R15-20 would make a
difference, I used R21-28, insulate by R value not inches of foam
there are alot of sites that give optimal needs.
I believe that's not true. If you consider the path that heat takes
to get from a basement wall below grade to the cold air outside, in
elevation view it is roughly a semicircle from the basement wall to
grade. So if you interrupt that path any point with insulation,
you'll reduce the heat loss. This is also the reason that insulating
the upper part of the wall below grade is most important, as that is
the part of the wall with the least soil insulating it.
The mass of dirt, energy it holds, and low R value of dirt makes this
idea sound very wrong, id bet anything multiple temp sensors buried
would prove this, unless someone can show some proven writings to this
There's heat coming from the center of the Earth, right? Once you get
down below a certain level the temperature stabilizes and what's
happening up above doesn't affect the soil temperature. Think of it
as holding the existing soil temperature in, and not the temperature
above out. Might make it clearer for you.
Check out the Building Science web site for cold climate construction
Right, I went to the earths center, it was hot as hell, it melted my
timex. If I get this right even you think a wing, a piece of
horizontal insulation buried without 98% of the insulation touching
the sctructure will affect the colds transfer to the building and
reduce it? I say its a nuts idea. The low R and energy holding quality
of mass earth will simply bypass-go around the foam, I bet a temp
sensor above and below the wing will be equal. I say alot of work, no
effect. Now if the wing went out 25 feet it might help but never
payback, im in chicago area and below grade basements are still 65f,
they were 64f at -20f this winter.
Think of it this way: the part of the basement wall that is just below
grade is normally insulated by just a little bit of dirt between it
and the cold air. By installing this insulation wing, you are
improving the insulation of that segment of the wall. The heat
transfer from it to the cold air may still go primarily through the
soil, bypassing the piece of insulation, but that's a longer path.
I'm not saying that this method is as effective as putting the
insulation against the basement wall, but it still is effective.
If it worked at all it would be the cheapest way to improve R value on
new Construction and would be heavily touted and heavily pushed by
insulation manufacturing companies, you know, the ones that will make
a buck from it, and as well EnergyStar. I have yet to see any adds
from insulation companies, [the ones that profit] or any testing or
testimonials or anything regarding this idea. My logic, of seeing how
dirts mass transfers temps makes me think it wont do anything, ever.
Now against a structure works. If this idea worked why hasnt something
like Pearl lite, or another organic insulator been poured , buried
around houses for hundreds of years. Where is the testing to prove it
works, not theory. Where are the articles that recomend it.
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.