Confused which is the best solution for the 2nd floor radiant heating on wood truss. Zurn advises pex under the floor coiling through the truss, Roth panels, ecowarm, warmboard, sunboard and list goes on. Any advice will be appreciated. Building a Nudura ICF home, unfinished basement,1st fl insuldeck with 5" concrete (2200 sq ft), 2nd FL wood truss (1500sq ft). All fl ht is approx 10' except the iving rm 20'. 1st FL i am thinking of going with ZURN 1/2" pex embedded in concrete.

For the 2nd floor, putting PEX under the subfloor is the worst performing HR emitter by a large margin. A thin slab HR emitter has the best performance followed by WarmBoard and then other above-floor HR emitter approaches. For the 1st floor, putting PEX in a standard slab is the best performing HR emitter by a large margin. Also need to have adequate insulation below the PEX too. And the HR system should be properly designed which first involves a room-by-room MJ8 heat loss analysis and then a design that provides the room-by-room circuit PEX spacing, supply/return temps and flow rates to generate the required room-by-room heat gain. HR design isn't rocket science...like my husband once did...but it does take some intelligence and knowledge that the vast majority of HVAC companies unfortunately lack.

- Pex in slab is a GO then, but clarification on "Also need to have adequate insulation below the PEX too"? Do i need insulation under the concrete slab? The Slab is 9" EPS all areas of the house and 12" EPS in garage area (insuldeck) with 5" concrete on top. I wanted to keep the pex about 2 1/2 inch from the finished floor since there will be thinset and 12mm tiles. Zurn has calculated 1st and 2nd so will just ask him to remove the 2nd floor, since they only have subfloor option.

- Appreciate the advise of NOT installing pex under subfloor of wood floor truss. "A thin slab HR emitter has the best performance followed by WarmBoard and then other above-floor HR emitter approaches", please correct me in my understanding - Is it from the bottom 1st wood truss then something like advantec board then shluter, thinset and 6mm tile?
- Warmboard and Ecowarm are quite pricey any other recommendations?
- Is it ok to mix Zurn pex system on the 1st floor and some other company system on the 2nd floor and then tie all of them together?

We have never used Zurn for anything so I can't comment on their system. We also don't like to comment on some other company's design either.

Typically, one puts at least 2" of EPS insulation under a standard slab. How many inches is appropriate for required R-value really depends on the local climate...hence the need for proper MJ8 and design. We have 4" EPS under our southern OR slabs...likely considered over-kill by many...but we heat both our buildings (2400 & 1600 SF) for about $30/month using simple and relatively cheap 4 and 6kW electric NextGen boilers...and for about $15/month if we wood fire up our masonry heater (sort of a heat battery...) for 60 minutes every other day. Construction photos of our place that we largely did with only our retirement hands can be found here:

https://www.borstengineeringconstruction.com/About-Us.html

Yes, WarmBoard is crazy expensive but it does perform very well...much better than any above-floor tube and plate system. Below-floor systems are non-starter for us. John Siegenthaler's Modern Hydronic Radiant Heating is the best source of reliable HR design and installation info. However, it is a very expensive book too but it is often available in libraries (if not banned for having truthful info) and desired/needed excerpts can often be found online too.

2nd wood floor is my concern now since Warmboard or Ecowarm (very thin alum sheeting) are expensive, appreciate any suggestions on other alternatives that are not under the subfloor?

1.5" thin-slab using gypcrete or a similar product is what we typically recommend over a ply or osb subfloor if the floor structure passes muster. Otherwise, we recommend mini splits...we like their efficiency...I don't personally like their looks, sound and air drafts but everything is a tradeoff. When we were in the business of designing/building multi level houses, we would typically do ICF walls and standard slab floors on all levels. Then HR is dirt cheap, simple and maximum performance...and you can have polished or stamped concrete and save money by not having to finish floors with wood or other "insulation" that then kills HR performance. I always try to convince folks to consider all aspects of what they want and then do an integrated design that gets it done at minimum overall cost...but unfortunately most folks just arrogantly and blindly rush into the design/construction phases in a series of clueless steps and then encounter issues and additional unplanned expenses along the way...which us contractors don't mind to much...

@sailawayrb appreciate your honest opinion and guidance/time. What is HR in construction term that you mentioned above?
Mini splits is not going to work for me due to the reasons you mentioned. It is an ICF home all the way to the roof and i wanted to cut cost by having wood truss second floor instead of complete concrete 2nd floor, but still want tiled floor instead of any other material with radiant floor heating. Would you advice this - wood truss > Advantec OSB > Roth panels with pex > Schluter > thinset > tiles?

Hydronic Radiant

Yes, what you suggest will work reasonably well. Tiles will greatly help as well. Be sure the floor surface temp in any room doesn't need to exceed about 85F in order to generate the required room heat gain which may start to feel uncomfortable to bare feet and may cause thermal expansion and contraction issues with the tile.

PEX in 1-1/2 of concrete is the best and cheapest other then having to glue down flooring. Remember it heats up and down unless you insulate between floors on the interior...I have built two houses and turned off the upper floors on one and the lower floors on the second...

Very true. If you don't have adequate insulation below the PEX in interior floors, you will lose controllability of the living space temp below these floors. But at least this downward heat is still retained within the building and isn't lost unlike the downward heat from inadequately insulated slab-on-grade floors. And if that living space is a basement that doesn't require accurate temp control, this can be a good approach to save some HVAC and annual tax money by declaring it unheated and non-living space. One just needs to properly design it and configure it at the appropriate time to accomplish this objective.

Happy Holidays!