- Longevity
- Comprehensive, non pro-rated 25 year warranty.
- Durability
- Can't be damaged by normal jobsite conditions.
- Simplicity
- No special tools required.
- Flexibility
- Tighter bend radius allows for entry into hard to reach areas.
- Kinkability
- Can't be kinked.
- Temperature Range
- Highest 180°F and lowest -30°F.
- Crush Resistance
- Drive wheel barrels or the concrete truck right over Onix and keep on going.
- UV Resistance
- Whether it's outside for a day or a year, Onix is resistant to UV degregation.
What is Onix?
Onix is a polymer-rich EPDM; comprising a five layer, synthetic, flexible tube.
The inner fluid channel is a peroxide cross-linked, high-grade EPDM wrapped with a flexible 00 grade aluminum oxygen barrier. Next is a peroxide cross-linked middle layer of EPDM, wrapped by spiral cords of aramid reinforcing. The cover is another EPDM layer.
What is EPDM and why was it chosen for this application?
EPDM (Ethylene Propylene Diene Monomer) is a flexible cross-linked molecule. The EPDM used in Onix is a high quality, polymer-rich formulation, utilizing relatively high ethylene grades with high molecular weights.
EPDM was chosen because it has a proven track record at high temperature applications. EPDM has been used in applications such as steam hose since World War II. Because of its molecular makeup, EPDM is an extremely stable polymer for high temperature applications.
What is aramid fiber reinforcing?
Aramid is used as a reinforcement to resist pressure. It gives Onix a 800 psi burst pressure at ambient and a 600 psi burst pressure at 180°F (compared to 325 psi burst at 180°F of PEX).
Aramid offers the best heat resistance over time of any reinforcing. Pound for pound aramid is stronger than steel. Aramid is used in bulletproof vests under the trade name Kevlar.
Is it true an Onix Staple-Up application costs less than PEX, even though the Onix tubing costs more?
Yes, Onix Staple-Up applications do cost less than PEX Underfloor applications. There are two main reasons. The first has to do with labor. Onix installs 2-3 times faster than PEX. This is due in part to the increased flexibility of Onix over PEX, not to mention the additional time needed to install the special fasteners required for PEX, such as clips and/or heat transfer plates.
These additional fasteners also increase the cost of a PEX system. Even though Onix tubing may cost more than PEX tubing, the cost of Onix with staples is about 40% less than PEX with metal plates.
Why can Onix be stapled directly to a subfloor and PEX can not?
Onix is comprised of a cross-linked EPDM compound that does not expand with temperature changes. Onix is the same diameter and length at 200°F as it is at 50°F.
No expansion means no wear on the tubing, no noise and no reduced heat transfer due to tubing moving away from the floor.
I've heard Staple-Up applications cause thermal striping. Is this true?
No. Onix Staple-Up does not cause thermal striping (objectable temperature differences). All radiant floor applications will experience some thermal variances in floor surface temperature on start up. This is due to the instantaneous load on the floor at that time. As the floor reaches steady-state conditions, this variance evens out, resulting in a very even floor temperature.
Once all properly installed radiant systems reach steady-state conditions (PEX or Onix), temperature differences are insignificant, resulting in a very even floor temperature.
I've been told heat transfer plates are required to spread the heat out across the floor. Why doesn't Onix need heat transfer plates?
Onix does not need heat transfer plates for two reasons. First, Onix is in direct contact with the subfloor, resulting in direct conductive, efficient heat transfer.
Second, Watts Radiant recommends all Onix Staple-Up installations use foil-faced insulation. The foil on the insulation "reflects" the downward energy back up into the subfloor. This reflected energy is spread out over the bottom of the subfloor, creating an even temperature.
Does Onix Staple-Up take longer to respond than other frame floor applications?
No. Response times are dictated by the thermal mass of the construction material, not the radiant tubing. All construction materials have a Specific Heat Value; this is the amount of energy required to raise the temperature of one pound of material one degree Fahrenheit.
The tables reflect the requirements for a 1,000 sf. room with a floor temperature change from 50°F to 80°F with a 50,000 Btu/hr output boiler. These numbers only reflect the time and load required to change the floor mass temperature, and do not take into account the additional load required to raise the room temperature, or to sustain the room's heat load.
| Time to reach Temperature | Heat Capacity | Start up BTU's | |
|---|---|---|---|
| 4" Concrete | 5.88 Hours | 9.80 BTU/ft3°F | 294 MBH |
| 1.5" Thin Slab | 1.93 Hours | 3.22 BTU/ft3°F | 96.6 MBH |
| 0.75" Subfloor | 0.66 Hours | 1.10 BTU/ft3°F | 33.0 MBH |
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