We are considering various options for the foundation & structural floor for an energy-efficient house in Colorado. The basement floor is below grade in some area, and at grade in others. We're debating the merits of an ICF foundation plus an ICF structural floor (eg QuadLock, LiteDeck) versus an ICF foundation plus a SIPs structural floor. We like the idea of the all-ICF foundation & floor from a solidity, simplicity perspective, but are concerned about the thermal bridge from the concrete floor -> concrete wall -> foundation footing and then the earth (which a SIPs floor eliminates). The concern is magnified by the fact that we intend to have a finished concrete floor with radiant heat - I don't want to be heating the whole planet...;) Has anyone built a house this way, got a solution for creating a thermal break between the ICF wall and the ground, or seen some information on the amount of heat that is lost to the ground in this sort of design? Thanks!

If I am understanding the situation correctly, I would think that if you're going to be using an ICF system, the ICF is already insulated and a thermal break. If I'm not understanding it correctly, you should talk to the quadlock representative or who ever you may be planning on going with. QuadLock offers an extra panel of insulation on the exterior of their ICF too if the standard one isn't enough.

Hope that helps and let us know what solution you find.

Sorry if I wasn't sufficiently clear: with the ICF floor there is a physical (structural & unfortunately thermal) connection between the concrete in the ICF floor panel and the concrete in the ICF wall panel. My concern is that since concrete is a good conductor of heat, this will allow the radiant heat in the floor to flow into concrete walls and downwards into the ground at the base of the foundation.

harveydan,

Have you considered using Geofoam under and around the foundation?  Geofoam will provide a thermal break.

Look at the foundations that are being used in PassiveHaus's in Europe. Basically a raft of insulation with walls built on top of it. This website has more info, http://www.isoquick.de/ You can do any walll from ICF to SIP on top of this foundation.

Use a product like Crete-Heat.

@jmagill: is there no need to have footings below the frost line with the isoquick foundation? What about issues from soil expansion and contraction?
@smartwall: are you suggesting putting CreteHeat or alternative insulation on top of the ICF floor and then doing another pour (seems expensive)? Because otherwise I don't see how it avoids the thermal bridge if you have a concrete structural floor that joins up with the concrete of the ICF foundation walls.

As in a wood foundation or Superior Wall you can use pea stone or crushed stone under your bearing wall with drain tile. This omits your expansion of the bearing conditions under
your wall system. Depth and compaction are important.

No footings at all. You do need to build a gravel base to spec. and I believe there is waterproofing etc. Basically a slab on grade with insulation under it. They did one of these buildings in Whistler for the Olympics. http://austria-passive-house-whistler-2010.blogspot.com/

Here is another one done in the UK.

http://www.scandinavianfoundations.co.uk/ Another one http://www.viking-house.ie/passive-house-foundations

We did a complete ICF project in Vermont using the AMDECK as the floor system. Here are some The radiant is poured on top of the AMdeck and is held inside the walls at least a foot. I would not be worried about the energy loss into the walls. The real question is weather you need to spend the money to put radiant in your upstairs slab. How large is the house? If you pour an ICF foundation with radiant in the basement slab that area will warm the entire house and with so little heat loss the whole house will have to be warmer. We have sold many jobs that people claim they never even turn there baseboard on in an ICF home that has a radiant basement slab. If you are building a super efficient building you can save money and still be comfortable possibly without the radiant. If you can span between the walls with conventional methods you may want to take a second look at costs. But if you are set on the elevated slab check out AMDECK

I agree with vermonticf, you won't need hardly any heating and cooling on an icf home, the basement slab will be enough. Plus you have to remember along with the lower heat loss you will have lower loop temperatures in the floor. This will mean that your in floor may not be sock worthy even though its keeping up with the heating demand.

http://www.viking-house.ie/passive-house-foundations

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