Will be building my own icf and was considering radiant in slab heat closed loop for the basement, two thermostats(in floor & 5ft above blab), w/ 1st floor forced air .Also considering stapled tubing under floor .
Reason being for the forced and radiant is since heat rises the temp in the basement should be pretty stable keeping the upper flooring comfortable. All alimented w/natural gaz  and located near ottawa.
Is this a good combo?? or am I out in the field.

The concept that you can basically heat the first floor by the stratified air from a basement slab has been around awhile, but it provides considerably less comfort for somewhat lower efficiency. Doing the first floor as a separately zoned staple up is far preferable and more comfortable (even at lower thermostat settings) than forced air Be sure to insulate between the staple-up and the basement or it'll overheat the basement.

With a radiant slab there just isn't a very large air stratification, and it's uncontrolled- the first floor won't feel very warm under foot.

Ok point taken,
What about the usual forced air duct you see under the windows to prevent
win. to condense. How is this issue taken care of w/ no air shot up?

Preventing condensation is secondary. The primary reason for having a register under a window is because windows cool the air in the room and you can get a down draft of cool air from the window. Having the register mixes warm air with the cool air from the window and creates a more comfortable condition. To a great extent this is historical because of leaky windows. With good quality windows (you're not going to go cheap on windows in an ICF house, are you?) room air doesn't get cooled very much by the windows and the windows leak very little.

There's a recent thread here somewhere about window condensation in an ICF house. Search for it. You'll find it interesting.

BTW, in your first post you say "heat rises". Heat doesn't rise, heated air (or any fluid) rises. Heat goes from warm to cold in any direction, up, down, sideways, whichever by conduction and radiation. It goes up only by convection.

B4 your decide to go radiant on the first floor - consider this:

Your heating load should be greatly reducted by the nearly airtight ICF construction. Also, considering the airtightness of the ICF, mechanical ventilation is not an "option" - you HAVE to have it - so, you need to run ductwork. If you also want A/C, you are looking at ductwork in some form.

All this points me towards a forced air 1st floor, combining systems, saving money and redundancy. Not to mention the loooooooong payback of a radiant 1st floor in a tightly constructed house. I don't buy the 'radiant is so much more comfy' argument. I can't tell the difference.....

I'm not here selling something - just a well researched guy getting ready to build (ICF or SIP - jury is still out :-)

Good observations in general, But "I can't tell the difference....."


You would be the first.

To know if you'd be able to tell the difference or not, you simply have to do a heat load calculation. No need to guess.

Or maybe the second, depending on just how low the heat loss is.

Folks in super-tight, super-insulated houses (R40 wall, triple-pane windows, etc, etc.) would have to run radiant "hot spots" to have areas of floor that actually felt warm.  IIRC the Riverdale Net Zero home project in Edmonton Alberta had a heat load sufficiently low that heat distribution was via "barely forced tepid air" circulation via the HRV ducting.  A full radiant floor there would only be a few degrees above ambient- very hard feel, providing very little (possibly negative) efficiency improvements.  A radiant "hot spot"  in each room might feel nicer though.

Assuming this is standard ICF construction with a clear-wall value of R20-R30 and a R60-R70 roof you can still get the cushy warm radiant floor effect by selecting only areas to be warmed.  But in an average lower-48 climate you may be also able to heat a structure like than more efficiently (& still comfortably) with a tepid-air hydronic coil in a low/variable speed HRV air handler, as in the Riverdale project house. Almost all standard hot air furnaces or hydronic boilers are likely to be overkill in the first place, if the building envelope is sufficiently well engineered & executed.  I'd agree that redundant systems just adds to the expense, not the comfort- either go with zoned hydronic/radiant or hot/tepid air, not both.

There's a bunch of info online about the Riverdale project, but a technical summary lives here:

http://www.riverdalenetzero.ca/RiverdaleNetZeroProject-TechnicalProposal.pdf

and the (9mb- watch out!) presentation slide version lives here:

http://www.riverdalenetzero.ca/PRESENTATIONS/Riverdale_NetZero_energy_home_--_presentation.pdf

Not necessarily true.

ICF construction allows for such things to occur, of course. But, people have this strange habit of putting in windows. Upshot is, most ICF houses I come across, while well insulated, are nowhere near "superinsulated" in terms of overall energy efficiency, and while the floors are not always warm per se, the comfort level is undoubtably greater than the results with forced air.

If you keep the glass under control, then it is possible to have the scenario you discuss. And good luck in most cases getting people to actually do that.

Wall construction method only helps the wall and infiltration heat loads, people.

Far too many questions without the requisite heat load being done first.

Rob speaks to my point. Few houses in the lower 48 are built to Super-insulated standards. I design "redundant" systems every week, I call them integrated.

Starting with a sealed combustion ModCon boiler, indirect-fired water heater, radiant floor in the othewise cold slab, fan-coil with attached HRV for second floor zoned heating and A.C. The boilers, fan-coils and HRVs are getting smaller all the time to fit these frugal design criteria.

This is a cost effective comfort system which - with outdoor reset built-in - can make for warm floors a good part of the season.

I run the fan-coil off the water heater for a simple two temp. system.

This is the type of info I was looking for .
BTW Investing in outer shell, windows and ceiling/roof, which is where it should be, natural gaz as elec. are available, leaning towards gaz for efficincy.
Thnx for the pros and cons.
Badger, which tankless combo do you recommend for domestic and radiant combined?
Cheers!

You are on the right track. There are some issues with the tankless combos (water side). Love the Excellence that Rob recommended to me awhile back.

Navien is coming out with a combi, condensing boiler and their brilliant design includes a small buffer tank for DHW.