Onyx revisited

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that have a lot of nail points to work around. Very flexible.

I'm not convinced it has the conduction contact as indicated. I painted some with a thick yellow paint and stapled every 6 " to see.

Squishing the staple tighter only seemed to flatten the tube on the staple contact, not tighter against the floor, as seen here.

I think a lot of the underperformers were due to a staple pattern way too wide. Then it becomes a suspended tube installation :)The weakest of all transfer.

The earlier Entrans were much more supple, and they did contact the floor surface much better.

A good reflective layer may be the key to some of the performance, after all, if the conduction transfer is weakened.

hot rod

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Ron Huber

Onix revisited

I know we have gone over this over the years. But, I work for a wholesaler now and the Onyx question has come up, according to the Watts design software it comes up with some relatively low water temps for the design conditions compared to pex with plates. Can somebody convince me that it really works? Sounds too good to be true, but if it really works I am not too old to change!

ALH_4

Onix

The output charts I have seen seem very optimistic. As I remember the fluid temperatures were approximately the same fea indicates for a Thermofin floor. That can't be right. Obviously it can, and does, work. I doubt it performs as well as extruded plates.

Not having first hand experience with an onix staple up system, I guess I cannot say much more.

-Andrew

Leo G_99

if installed

as directed, stapled every few inches and "squished" flat agin the underfloor, it seems to work as indicated. Of course in my area, it rarely gets below 20* F. Wonderful to install, just find that I use the 3/8's more then the 1/2 as I seem to be getting weaker in my old age!

Leo G

Unknown

They seem to be giving a "bonus" in their ratings and their software for using a layer of reflective insulation under the tubing.

Personally, I would never design a system around a reflective barrier's long term performance... but that is a very, very debatable stance. They may well be right to do it, and I just too "conservative".

Ron Huber_2

reflective layer

The contractor that is my customer is doing this in his own house, he plans on ripping sheets of foil faced urethane and attaching them to the underside of the top cord of the TGI joist which will give him about an inch+/- of air space, sound like that will work?

Ruthe Jubinville

Insulation

I have done many jobs that the contractor used foil faced urathane in 1" or sometimes 2" under the onix' My kitchen has 1" against the top cord of the tji joists with pb tubing above

Ruthe Jubinville

Insulation

I have done many jobs that the contractor used foil faced urethane in 1" or sometimes 2" under the onix' My kitchen has 1" against the top cord of the tji joists with pb tubing above

Tim Doran

The Math

The math says that this is physically impossible. Here's why. First off the thermal conductivity of epdm rubber is lower than that of pex. Second, the wall of the Onix is thicker than that of any ASTM listed pex. Third, as Hot Rod stated, the tube contact only seems to be at the staples. Based on the numbers which are straight out of the ASHRAE handbooks suspended pex will outperform staple up EPDM so there is no contest when it comes to EPDM vs. plates.

Tim D.

ALH_4

Agreed

Tim, you are absolutely right. When ever I have mentioned this in the past, I have met with people who have said, "it works just fine", and it does in some cases. Personally, I think this argument stems primarily from the fact that Onix is easier to install than pex and plates. This keeps the labor costs, and neck pain down, but keeps the fluid temp up. Conduction is the key to achieving the lowest fluid temperatures possible, keeping floor temperatures as even as possible, and maximizing the overall output of the radiant floor in cases where heat loads are high. Extruded plates are also an excellent way to build a radiant wall. When it's -24F outside and 96F fluid temperatures will maintain 68F inside, it's hard to argue with extruded aluminum plates. That being said, each system has its positive points and negative points.

-Andrew

Boilerpro_5

Another real life feedback

I have a system with a combination of suspended pex and EPDM under floors with similiar per square foot loads. The EPDM easily outperforms the suspended Pex. Plated Pex is likely another whole separate issue. However, for most typical heat loads of newer homes that are not walls of glass(15BTU/sq foot or less) EPDM can be very attractive with much lower operating temps than suspended pex and much lower installation costs than Plates. It seeems to fit well between these two extremes...Inexpensive to install but high water temp suspended and very expensive to install but lower water temp plates. I mix and match myself to meet a consistant water temp in a system.....Using suspended where loads are low and plated where loads are high and then run the system on full reset. Keeps the cost to benefit ratio very high....Only use expensive Plates where they will provide benefit.

Boilerpro

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If you compare the price

1/2" Onix, including the connector and clamp, the price per foot is really close to 1/2" pex and plates. But I agree the real savings is in the labor. EPDM staple up is a one shot install.

Keep in mind the insulation cost difference also. If you go with an aluminized layer then batts to R-19. As well you should with the higher temperature suspended and staple up tube only installs.

Transfer plate installs use plain fiberglass batts or even spray foam for really tight insulation detail.

Rare to find a transfer plate install that needs over 130F supply. This plays nicely to mod cons. Figure 150 and up fo many suspended and direct plateless staple ups.

hot rod

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joel_19

15 BTU

I guess that depends where you are located but up here they make the new homes as loose as a goose and every couple years we have several windy bellow 0 days. if you count on 15BTU in Lawsuitachussettes your lawyers number better be first on your rolodex. Because if it's not holding 70 for even acouple hrs you will be getting the call.

We refuse to install any type of non plated system and even at that plated is mostly floor warming backed up by hydro air. We prefer on top if we are on the hook for the output.

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joel_19

15 BTU

I guess that depends where you are located but up here they make the new homes as loose as a goose and every couple years we have several windy bellow 0 days. if you count on 15BTU in Lawsuitachussettes your lawyers number better be first on your rolodex. Because if it's not holding 70 for even acouple hrs you will be getting the call.

We refuse to install any type of non plated system and even at that plated is mostly floor warming backed up by hydro air. We prefer on top if we are on the hook for the output.

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