We are planning on building an ICF house in the next few months slab on grade. Footers 24” deep minimum (code) poured on grade with approximately 12” fill inside to raise floor above ground level, floor poured against ICF wall, insulation under slab. Anyone use a thermal break between footer and ICF wall? Would this not help keep cold from transferring to wall. Water seepage through thermal break is not a problem site is well drained away from house. I have been visiting this site often lot of knowledge here, any advice appreciated

 

Thank you, Jerry Green (KY.)

From what I understand you are saying is the interior is being filled 12" above the footing, underslab insulation will be placed under the slab...right to the ICF wall. You have just encapsulated the whole thing, no problem.

Jerry,
Always interested to hear about another KY project.
Where are you located?

Wes I located in Brandenburg (Meade County) Ky. Will the cold from footer not creep up into walls. What if 2"of insulation was pressed down over the rebar stubbed up out of footer and wall was set on top of insulation, it would be compressed by weight of wall. Would this be a bad idea?
     Jerry Green

place 4'x8'x3" sheets of foam on top of footing on the outside pressed up against the ICF all the way around the exterior of wall. This will prevent frost from getting through you footer. Check out some of the ICF manufacturers web sites and look at their Typical Details for Shallow Footings . Section 5.3.3 and 5.3.4 in the Logix manual and C-12 in Nudura's manual.
hope this helps!
Paul Stevens

"wall was set on top of insulation, it would be compressed by weight of wall. Would this be a bad idea?

Yes, because you cannot control the amount of compression from the "weight of the WHOLE HOUSE", which rests on those footings!

Thanks for the information .

Jerry Green

Jerry,

I have seen High density foam footer forms, European source. But in the big picture, Delta T and cross sectional are key. First, if your footers are deep, you are looking at 40 degF footer depth, not so big a temp diff. Second, the area of exposure is wall thickness by wall length, small compared to flat wall area. Lastly, a temp gradient forms in the wall. This gradient length is quite long, wall height. Unlike a sheet of glass, large surface area short temp gradient.

Patrick T

Since this is a similar topic I have a question. Our ICF house in mid-Minnesota will be finished up in March. The footings are to code so they are 4' or more below grade. Our house has a basement and the slab sits on top of the footings with 2" of XPS and a reinforced poly vapor barrier. Since the ICF concrete core is primarily heated by the footings contract with the earth, I was wondering if I could have helped keep the ICF concrete core temp higher by putting 2' or so of the XPS horizontally out from the footing to the exterior of the foundation. Kind of like a Frost Protected Shallow Foundation. Would that have it even made a difference??? The house seems to be super efficient. Right now the heat is all electric plenum until the air source heat pump is hooked up. Last week our project manager turned the heat down from 66F to 55F and it took well over 24 hours before the electric heat kicked in again. I could see this via the our electric usage graph I can view at our utilities web site. The average temp during that period was 17 below zero F.

No mlevendo, that would not have helped. The whole reason that you need 4' minimum frost walls is that below that depth, our midwest winters cold doesn't penetrate that far. The ground doesn't freeze that far down, so your footers can't be compromised by freeze/thaw conditions.

For the original poster - I would encourage the use of a dampproofer such as spray on asphaltic based waterproofing material, between the footer and the ICF. This will prevent moisture wicking. That's what I will be doing on my ICF basement...

I know that at 4 feet down the frost does not reach the footing to cause heave but the ground temp at that 4 feet could still be 40F. If there was horizontal insulation I was thinking that the heat leaking from the slab and the normal earth temperature would raise the temp of the footing and thus raise the temp of the concrete core of the ICF. This would then reduce the delta t of the temp of the interior of the conditioned home and the concrete core making the house even more efficient. Take better advantage of the geothermal energy. Too late now though since it is already back filled. Maybe someone else can find out if it would make a diffrence and take advantage of this info when building their ICF home.