Posted By ICFHybrid on 19 Jan 2012 01:28 PM
Have you considered where in the slab (depth) you're going to put that PEX?

Interesting points you make that I have read a bit about but in my building situation, I was informed that the radiant heating system would preform better in the long run if it's placed on the foam.  This was directly attributed to heat gain in the ground underneath the slab but I'm all ears when it comes to pros and cons about this.

My structural engineer wanted 5 inch slabs as they are a key component in locking the building diaphram in on the hillside that it is built upon.
Maybe I should explain a little more about my system....

The ICF house is 3 levels.  The 1st floor has 8 inch ICF walls 14 feet tall of which 1/2 of the wall surface area is burried in the dirt.  The 2n'd floor has 8 inch walls 12 feet of which 1/3r'd of the wall surface area is burried and the rest of the ICF walls system is 6 inch concrete walls on up to the 3rd floor top plate. The entire roof/attic has 14 inch thick R48 sprayed foam open cell insulation. So the entire structure is closed.

The first floor (bottom) is a 5 inch concrete slab with 2.5 inches of EPS under it.  To be used as a workshop but able to be turned into a mother in law down the road.
The 2’nd floor has 2 bedrooms that sit over top of the first floor (will need joist heating) and the rest of the entire floor is concrete. Same set up, 5 inches of concrete with 2.5 inches of eps under it.
The 3rd floor is all joists that will need to be heated. 

On the 2nd floor, I have a machine room that houses all the equipment.
The 2nd floor will have a pellet stove that can be used for quick heat pickup that points towards the stairwell so heat can rise into the 3rd floor.  

We have geo exchange piping burried behind the 1st floor walls 14 feet deep on up to about 6 feet beneath the FF of the 2n'd floor. This piping is directly under the 2n'd floor concrete slab. Lain in a slinky pattern, the total of 2 loops each 500 feet are seperated by an ICF wall on each side inside the building under the 2'nd floor slab of the building. Totaling 2000 feet of geo exchange pipe. Another 500 foot loop is installed on the side of the 1st floor walls on the exterior of the building. Hope that makes sense....but let me know if you need more clarification.  The geo totals 5 loops.

So here's where the fun begins.  I was told that we only need 1500 feet of geo piping which is required to run the geoexchange heat pump for this house.  This allows me 1000 feet of piping that I can use to store heat in either of the compartments per say.  Retaining this heat through the summer, I am told I can pick it up and use it for heating the radiant floors in the winter.  After 4 years, I have been told I will need very little heat or none at all.  (I find this hard to believe).
Additionally, I was told that our 58 degrees ground temperature may be used to chill the concrete slabs if needed in the summer but highly unlikely.

Cooling 1.7 tons is only needed on the 3rd floor so I wanted to install an air to water slim line fan coil since the floor plan is very open.  If any cooling is needed on the 2n'd floor, I'd do the same.

So lets talk about what I’m looking to obtain. I would like to keep my domestic hot water separate from the radiant heating system. I would like to have the ability to use a tankless water heater as a back up to the geo thermo heat pump. I would like the ability to add solar hot water collectors and possibly in the future, an exterior boiler.  This should handle the heating for this home.
 

Our electricity is expensive here so propane is the most efficient heat source and may use the tankless heat source most often. Depends on how well the geo exchange heat pump works though. Other info for conditioned space would be to have an ERVor HRV for fresh air (not sure which one) but each bathroom has an exhaust fan.
I would like to find a decent user friendly control system for the entire BMS as well but I'm confused here.

All our windows are vinyl Milgard Tuscany with 3 D max coatings with low e.  The laod calculations have been completed and I can share them if needed.

For the record, I'm not a contractor but a home owner/builder looking for the best direction so I can do the right thing for this house.
Any input you have is truely appreciated.  I'll try and attach a few pictures.

I'm located in Placerville California at 925 feet elevation in a river canyon.

I'm all ears when it comes to pros and cons about this.

Posted By ICFHybrid on 20 Jan 2012 09:38 PM

I'm all ears when it comes to pros and cons about this.

Normally, putting the tubing right down on the insulation only increases the heat gradient there, causing higher heat loss. Same for the theory of soaking the underlying ground with heat. If that was true, we might as well just stick tubing below the insulation to speed the process.

However, it appears as if that is what you are doing.

Let me get this straight. You will be using the geo heat pump to cool the house in Summer, dumping the excess heat in the ground in close proximity to the house and then using the heat pump to suck it out of the warmed ground to heat the house over the winter?

I also buried pipe around the house in the backfill for potential geothermal use but I have not done anything with it.

The large slabs

Posted By ICFHybrid on 23 Jan 2012 09:39 AM

I also buried pipe around the house in the backfill for potential geothermal use but I have not done anything with it.

If you take heat out of the ground to put it in the house in the winter, won't you just be chilling the ground and eventually, the rate of heat loss from the foundation? What was the rationale for putting the ground loop so close to the house?

The large slabs

are you referring to the concrete in the ICF?