Uponor Solutions:
Residential Radiant Floor Heating

Radiant Floor Heating FAQs for Architects

How does radiant floor heating work?
How long has Uponor Radiant Floor Heating been around?
What are the main components in a radiant floor heating system?
What is PEX tubing?
What is the difference between PEX-a, PEX-b and PEX-c tubing?
What are the temperature and pressure ratings for Uponor PEX?
What are the Uponor PEX manufacturing standards?
What are the Uponor PEX listings?
What are the Uponor PEX codes?
What installation methods work best for installing radiant floor heating systems?
Is a supplemental ventilation system necessary?

In a radiant floor heating system, warm water flows through flexible plastic tubing called PEX that is located underneath or within the floors. (PEX is an acronym for crosslinked polyethylene.) The PEX tubing carries the warm water into specific rooms or “zones” to effectively heat people and objects in every corner of the room.

Uponor (formerly Wirsbo) was the first to bring radiant floor heating to North America more than 40 years ago. And the concept of radiant floor heating has been around since ancient Roman times. Radiant floor heating has been, and continues to be, used in many countries around the globe to effectively bring comfort in even the most extremely cold climates of the world.

The main components in a radiant floor heating system include a heat source, pumps, manifolds, PEX tubing and controls.

PEX is an acronym for crosslinked polyethylene. It is a flexible, durable, corrosion-resistant product that possesses distinctive properties that make it ideal for radiant floor heating and plumbing systems. There are three different types of PEX tubing: PEX-a, PEX-b and PEX-c. Uponor manufactures PEX-a tubing, which is considered the superior type of PEX in the industry.

All three PEX manufacturing processes generate tubing that is crosslinked to varying degrees and are acceptable for potable-water and hydronic radiant floor heating applications.

  • PEX-a is manufactured using the  Engel or peroxide method
  • PEX-b is manufactured using the Silane method
  • PEX-c is manufactured using the E-beam (electron beam) or radiation method

Uponor manufactures PEX-a tubing. The PEX tubing industry considers PEX-a superior because the crosslinking is done during the manufacturing process when polyethylene is in it amorphic state (above the crystalline melting point). Because of this, the degree of crosslinking reaches around 85% (higher than PEX-b or PEX-c), resulting in a more uniform, more flexible product with no weak links in the molecular chain.

Uponor PEX carries the following hydrostatic temperature and pressure ratings.

  • 200°F (93.3°C) at 80 psi
  • 180°F (82.2°C) at 100 psi
  • 120°F (48.9°C) at 130 psi (½" tubing only)
  • 73.4°F (23°C) at 160 psi

In accordance with ASTM F876 Standard Specification for Cross-linked Polyethylene (PEX) Tubing, the excessive temperature and pressure capability for Uponor AquaPEX® is 210°F (99°C) at 150 psi.

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Uponor PEX conforms to the following listings. Be sure to visit the listing agency’s website for complete details.

  • cNSFus-rfh
  • cNSFus-pw
  • cNSFus-fs
  • cQAIus
  • UL
  • CSA
  • WH
  • ETL
  • PPI TR-4
  • ICC-ES
  • BMEC
  • CCMC

Uponor PEX meets the following codes:


  • ICC
  • IPC
  • IMC
  • IRC
  • UPC
  • UMC
  • NSPC
  • HUD
  • UFGS
  • NPC of Canada
  • NBC of Canada

It depends on the application. For a concrete floor, it’s best to install the tubing before the concrete is poured. You can tie the tubing to wire mesh or staple it down to foam board and then pour the concrete over the tubing to embed the tubing in the slab. For plywood subfloors, you can use Quik Trak® radiant panels or Fast Trak™ knobbed mats. For joist-heating applications, where the tubing is installed between the joists under the floors, you can use clips to “hang” the tubing or use Joist Trak™ heat-emission plates. To learn more about these products, visit www.uponorpro.com.

Yes, ventilation is necessary to address the latent load and bring in the required fresh air. However, the ducts can be smaller which saves structural height.