In house planning stage, high altitude 8.800', cold Colorado climate, great solar available. Has anyone tried running pex in ICF walls before pour & using concrete for solar heat storage? Warming up the concrete would reduce heat loss.

Do a search and see if you can find a thread from somewhere in the past 4 or 5 years about pex in the walls. I think in that thread the heat supply may have been earth, but I don't recall.

It is a doable idea, but there are a lot of technical considerations you will have to work on. Heat load is the first. That may or may not be significantly different than the usual because of the thickness of insulation on the outside of the concrete compared to the total insulation thickness for interior heating only. Then comes solar collector sizing. Then that leads into costing.

If you have the wherewithal to do the calculations yourself, or an adventurous and cooperative heating consultant to work with, I'd say explore the idea. But most likely it won't pencil out cost wise.

Solar has not yet become a significant source for space heating, other than in passive solar designs. I think that is mostly because the area required to collect sufficient energy to make a big dent in space heating can be quite large and expensive. Also, if you need to incorporate cooling into your house, other than open windows, fans, or ventilators, the cooling system will often be the heating system also. To add solar to that is to greatly increase your capital investment.

Don't scratch the idea, but don't be disappointed if it turns out to be a dud.

Thanks dmaceld for input, I did search prior to my post. Didn't find anything. No AC needed.

My statement "Warming up the concrete would reduce heat loss." is incorrect. Actual heat loss to the outside would increase.

What I was trying to say: Warming the ICF concrete with solar would reduce my gas bill somewhat.

In my planned ICF walls & footers, there will be about 260,000 btus / 1*f heat storage available.

Tying solar into my planned radiant floor system would be difficult with the high temperature cast iron boiler I have already bought.

I realize that right now, solar is hard to justify costwise with gas rates being low.
I would like to find a way to use solar cheaply.
I don't like panels on roof, looks ,large hail, etc.
Don't want passive windows, I've had them in past home, insulated curtains were PITA with the closing / opening, this needs to be automatic, again $$

I will have a South facing wall with about 235ft2 am thinking of building verticle panels onto wall.

I have used the DOE online RESCHECK to calculate my design heat load (32kbtu at -20*f). Had to SWAG some inputs like infiltration. R23 ICF walls are about 20% of load.

Plans do inculde HRV, good windows, SPF ceilings, FPSF, well insulated radiant floors, etc.

http://www.radiantsolar.com/pdf/DOEREPORT.pdf I think this is what you are looking for. They are using the 2' of mass/earth below the floor as the heat exchanger. Not the ICF walls or the footing.