? on slant find heat loss calcs

Peter Groenewold

I'm not real familier with the Slant Fin Heat Loss software, but when choosing exposed wall factor, there is no choice for Insulated Concrete Form walls. Is there anything I can do here to make it work for me?

Thanks
Paul Shay
A Real Good Plumber, Inc.

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Unknown

Paul

you`ll likely have to Google-up the manufacturer of the ICF to come up with the appropriate U-factor, then manually put it in the S/F program.

Dave

Ron Gillen

U-factor

If you can get the r-value of the wall (mine was R-25), the U-factor is 1/25=.04 U-factor. If not, just use .04 it'll be close enough.

Paul_11

thanks to both of you

I am curious though, when you say your ICF was rated at R25 was that based on the thickness of the styrofoam insulation or the effective R factor of your ICF.
For example, i'm using Polysteel, which has 2.5" inside and outside. A laboratory would only rate that at R20, I believe, R10 for each 2.5". However, if you factor in the 55 degree geothermal heat that is coming up the walls, from what I hear it should be expected to funciton as if it was R50.
What do you think?
Respectfully,

Paul B. Shay
pshay@arealgoodplumber.com
LMP 1307
LMFS 654B
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Ron Gillen

ICF R-Value

Paul, I used LOGIX ICF blocks which are 2.75"/side rated @ R-4.13/inch. Whole wall construction, foam - 5.5"x4.13=R-22.715, 6" concrete @ R-.08 = R.48, Vinyl siding @ R-.61. 1/2" drywall @ R-.45, Interior air film @ R.68, exterior air film @ R-.17, Whole wall = R-25.105. If you are selling ICF blocks many advertise R-50 "equivalent". I have'nt seen them claim R-50. The equivalent comes from a comparison to fiberglass insulation which inherently loses effectiveness at lower temperatures, has convection currents further reducing effectiveness, has whole wall loses due to thermal breaks at studs, plates, etc. and allows far more infiltration than ICF. The result is that an R-20 fiberglass wall may have a whole wall loss of something closer to R-10. Therefore the ICF manufacturers say that to build this wall to perform as well as theirs, you would need to build an R-50 fiberglass insulated wall. I have'nt heard of geo heat rising in the concrete but would be surprised to hear that it has much effect in a wall 20 - 30 feet tall. Not my area of expertise. All this said, my best guess is that my home performs at least 30% better than my heat loss shows. Hope this helps.