r value of concrete

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M - 28 Oct 2006 00:46 GMT

I had an argument with a friend. I told him that concrete has little or no
r value if it isn't backfilled. Does anyone have the rating of straight 8"
thick concrete?

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Mike - 28 Oct 2006 01:15 GMT

>I had an argument with a friend. I told him that concrete has little or no
>r value if it isn't backfilled. Does anyone have the rating of straight 8"
>thick concrete?

ITs 0.08/r/inch

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dean_maiorano@hotmail.com - 28 Oct 2006 21:24 GMT

> ITs 0.08/r/inch

Dang, is there any way to insulate that with a sealing coat or
insulating additive (to floor paint)?

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M - 30 Oct 2006 00:19 GMT

>> ITs 0.08/r/inch
>
> Dang, is there any way to insulate that with a sealing coat or
> insulating additive (to floor paint)?

before back filling some folks are putting foam up. You can also insulate
from the inside. Backfilling makes for great r value but it isn't a good
idea to back fill right up to the siding ....

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Matt Whiting - 30 Oct 2006 00:29 GMT

>>>ITs 0.08/r/inch
>>
[quoted text clipped - 4 lines]
> from the inside. Backfilling makes for great r value but it isn't a good
> idea to back fill right up to the siding ....

It is a technical point I admit, but backfilling has no change to the
R-value of the wall. It changes the delta-T that the wall sees, but it
doesn't affect the resistance to heat transfer. If you are in a cold
climate where the earth freezes for 3-4' in the winter, then the top
half of the concrete wall will still lose a lot of heat. Adding foam
does increase the R-value of the wall and will help a lot if in a
location where the ground gets pretty cold in the winter ... or warm in
the summer.

Matt

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Homeowner Forum / Construction / October 2006

r value of concrete