Since its arrival in the U.S., crosslinked polyethylene (PEX) tubing has taken the hydronics industry by storm. That is primarily due to its reputation as being a durable, flexible, and, some might even say, more affordable option for radiant heating and snowmelt applications.

Manufacturers also tout the ease with which their PEX-tubing systems can be installed in radiant heating applications, noting that their latest offerings can shave even more time off an installation while improving accuracy.


Viega LLC, for example, offers a roll-deployable radiant mat system, called Climate Mat™, for use in facilities that are 10,000 square feet or larger. It is custom manufactured specifically for the job and comes pre-pressurized for immediate installation. A substantial labor savings of 30 to 50 percent can be realized using this system, said Josh Quint, product manager, heating and cooling, Viega LLC.

“A typical mat system will cut the installation labor by one-third to one-half of a normal hand-placed, circuit-by-circuit installation,” said Quint. “Not only is labor saved with the use of Climate Mats, consistency and uniformity of tubing space provides a uniform floor surface temperature, creating a greater comfort experience for the client. In addition, all attachments to the supply and return manifolds are above the floor for balancing access, and the mats are pre-balanced, ensuring a worry-free installation.”

For large commercial applications, Uponor offers the Radiant Rollout™ Mat, which is a custom-designed, prefabricated, and pre-pressurized network of Wirsbo hePEX™ oxygen-barrier tubing for radiant heating and cooling applications. The mats arrive on the job site in large rolls, and installers simply stake down the header of the mats and unroll them in one simple motion.

“This technology saves 60 percent or more on installation time and covers almost six times more square feet in the same amount of time it takes using traditional staple-down or tie-down methods,” said Stan Sveen, senior manager, light commercial segment, Uponor. “Also, because there is one supply header and one return header for each mat, it reduces the number of required manifolds by at least 60 percent or more, depending on the size of the mat.”

On the residential side, Uponor offers Fast Trak knobbed mats. With this system, installers simply place the preformed mats on the subfloor and then snap the tubing into place with the desired on-center spacing (available in 2-inch increments), said Kate Olinger, senior manager, single-family segment, Uponor. “This system greatly improves speed and accuracy when installing tubing in radiant floor heating applications, increasing installation efficiencies from days to hours.”

For controlling a radiant floor heating system in a home, Uponor offers the new Climate Control Zoning System II, a wireless technology that speeds installation and increases system efficiencies and control for the end user. “The system uses a technology called autobalancing, which allows the system to react 25 percent faster and provide 20 percent greater energy savings,” said Olinger.

Earlier this year, Rehau introduced the EVERLOC+™ compression-sleeve fitting system, which was designed to make PEX installations faster and more secure. With this system, the EVERLOC+ power tool cold expands the company’s RAUPEX PEXa pipe, then the same tool is used to compress the sleeve over the fitting to make a connection that is ready for a pressure test immediately.

“Our system combines the speed of a big-box store fitting with the premium performance of a PEX system that we have been innovating since 1967,” said Max Rohr, academy manager, Rehau. “The EVERLOC+ system allows contractors to use the same steps — two expansions, one compression — on the warmest and coldest days of the year, with no need to modify the process for weather. The consistent and active compression technique of EVERLOC+ makes it up to three times faster to install than other PEX systems.”

Watts Radiant offers a range of PEX tubing, including the PEX+ line, which is a four-layer product consisting of PEX, adhesive, oxygen barrier, and a protective coat that provides effective sound reduction. The company also offers PEX-al-PEX with an aluminum layer; PERT, polyethylene tubing similar to PEX but not cross linked and rated for high temperatures; as well as Onix, a synthetic rubber ethylene propylene diene monomer (EPDM) pipe developed specifically for radiant heat and snowmelt uses.

This expanded product offering allows Watts Radiant to support contractors in just about any situation, said Michael Breault, senior product manager, hydronics, Watts Radiant.

“One of the challenges installers face — especially if they’re relatively new to radiant heat or snowmelt work — is buying a set of connection tools, which can be quite costly,” he said. “Our tubing, depending on the pipe, can be joined by essentially all fittings, and we have the components or fittings to support that need — allowing installers to use their inventory of tools.”


Of course, the best products in the world will only perform as designed if they are installed correctly, and mistakes can be made when it comes to the installation of PEX tubing. A common mistake contractors make when they are switching from a metallic alternative to PEX is that they don’t maximize the benefits of a lighter, more flexible product, said Rohr. “Some installers use more fittings than necessary, instead of navigating around obstacles with the flexibility of the PEXa material. Also, by using bend guides instead of elbows, two connection points can be eliminated. If you install PEX like rigid copper, you won’t save as much time as you could.”

Using duct tape to identify tubing loops near the end of loop runs is also a no-no that commonly occurs in the field, said Kolyn Marshall, system engineering manager, Watts Radiant. “Installers will often attach the tape and number the loop, like ‘Loop 3 Supply’ or ‘Loop 3 Return.’ But this can cause problems unless the taped portion is cut off when the loop is attached to a manifold. The petroleum-based adhesive in the tape is harmful to PEX, and it’s accelerated by heat, either by sunlight, or circulated fluids.”

Speaking of sunlight, that’s another issue that contractors need to be aware of, because most PEX is vulnerable to UV degradation, and damage typically begins after 30 days of exposure. If there are job delays, the tubing is at risk, said Marshall. “Another challenge can happen when cable ties are used to attach tubing to re-wire, or rebar prior to a concrete pour. If an installer fails to cut off the plastic tails, they might protrude from the slab and compromise the surface.”

The single biggest mistake made in residential radiant installations — and in any other type of HVAC installation, for that matter — is the failure of the installing contractor to run a complete load calculation, said Quint. “An installation blueprint of manifolds and circuits would then be based upon such [incorrect calculation] for physical installation. Rules of thumb and guessing are never a good solution. Bigger is not better. Right sizing is a best-practice approach.”

When humans are involved in an HVAC installation, there is always the chance that mistakes will be made. Someday soon, though, a contractor might sketch a piping diagram on a tablet, and a robot will start putting the pieces of pipe together in the mechanical room, said Rohr. “Until then, we will keep making our products and tools smarter, faster, and easier to use.”

Non-PEX Option

Besides PEX, there are many different types of piping that can be used in radiant heating systems, including Aquatherm’s polypropylene-random (PP-R) Blue Pipe®, which utilizes a heat-fusion technique to make installation easier. “Rather than using glue, solder, or a mechanical connection, heat fusion bonds the piping at a molecular level, physically turning two pieces of PP-R into one and eliminating systematic weaknesses and fail-points,” said Barry Campbell, vice president of marketing, Aquatherm North America.

Aquatherm Blue Pipe is sized from ½- to 24-inch diameter and offers an optional multi-layer, faser-composite technology that allows the PP-R pipe to remain rigid at high temperatures and limits expansion/contraction, allowing it to handle operating temperatures up to 180°F at 100 psi. In addition to being ideal for supply and return headers, Aquatherm can also be used in smaller diameter loops for in-floor, field heating, and snowmelt. The company also has introduced, on a beta basis, the Aquatherm Black System®, which provides not only radiant heating but also cooling designed for installation in walls and ceilings.

Aquatherm also offers extensive heat fusion design and fabrication services from its Utah headquarters. This provides contractors with additional planning resources and the ability to receive simple-to-intricate manifolds, headers, and spools that can be quickly and easily plugged in at the job site.

Publication date: 10/30/2017

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