Most of my house is set for PEX in the slab on grade but over the basement (under about 20% of the 1st floor) there will be a section where we will have wood floor joists with the radiant stapled down and covered with chipcrete.  The plumber wants to use Oynx on this section.  Does anyone have any thoughts on the pluses or minuses of doing this?  Why not use PEX all around?

Personally, I don't like onyx. I have seen a bit too much "black sludge" in onyx systems.

What would the advantage be? Onix is usually used as stapleup subfloor. Even Watts radiant sell barrier PEX for staple "down" systems with Gypcrete cover. I'm with Rob.

Onix pipe is about 4 times the cost of a pipe like our RHT pex barrier, while very flexible (Like working garden hose) it is an overkill, epically if you are using it in a slab or topping pour. It is easy to use in a staple up, I have also seen it specified for heliports in Alaska, again extreme out door UV exposure. Other parts of the equation are how the plumber intends to heat the water? Fuel? length of pipe runs he has in mind.
Dan

I just got a letter about the entran2 law suit.
I think that they are on to entran3 now, which I have some installed. hopefully they learned from their mistakes

Onyx is not Entran.