Top Questions
Radiant Heating

What is radiant floor heating?
Uponor Radiant floor heating is a comfortable and efficient form of heating where warm water circulates through flexible, specially designed PEX tubing installed under the floor. The heat radiates evenly up through the floor warming people and objects in the room and providing more comfort for less money.


What makes radiant floor heating so comfortable?
Unlike traditional heating systems that just warm the air, radiant heating warms the floor and the objects in contact with the floor. The entire floor distributes a consistent, even and quiet heating. There are no drafts and radiant floor heating takes the chill out of cold tile, marble and wood floors.


How long has Uponor Radiant Floor Heating been around?
Uponor Radiant Floor Heating has existed for nearly four decades. We've been making the PEX tubing used in our radiant floor heating systems since 1970, longer than any other PEX tubing manufacturer.


Can the floor get too hot?
No. A properly designed radiant floor heating system will deliver comfortable warmth that’s a pleasure to walk on — especially in bare feet! If additional heat is needed to satisfy the heat load, additional warmth can easily be added by installing radiant walls and/or ceilings. Uponor offers technical design support as well as design software to ensure your system offers the greatest comfort and efficiency possible.


If I install radiant floor heating, can I still install air conditioning?
Sure you can. In fact, separate heating and cooling systems really make the most sense. Radiant floor heating keeps the heat near the floor where it does the most good; and air conditioning ductwork is placed only where it is needed to cool your home. The result is optimal comfort and efficiency all year.


Should I use Wirsbo hePEX™ or Uponor AquaPEX® for a radiant system?
It depends on the application. Typically you will want to use Wirsbo hePEX which features an oxygen barrier to protect ferrous components in a closed-loop hydronic radiant system.


Do you need a supplemental ventilation system?
Yes, however the ducts can be smaller which saves structural height. Ventilation is necessary to address the latent load and bring in the required refresh air.

Codes and Standards

What are the Uponor PEX standards?
Uponor PEX and associated fittings are manufactured to the following standards:
• ASTM F876 “Standard Specification for Cross-linked Polyethylene (PEX) Tubing”
• ASTM F877 “Standard Specification for Cross-linked Polyethylene (PEX) Plastic Hot and Cold Water Distribution Systems”
• ASTM F1960 “Standard Specifications for Cold Expansion Fittings with PEX Reinforcing Rings for use with Cross-linked Polyethylene (PEX) Tubing”
• ASTM F2080 “Standard Specifications for Cold Expansion Fittings with Metal Compression Sleeves for Cross-linked Polyethylene (PEX) Tubing”
• CSA B137.5 Thermoplastic Pressure Piping Compendium
Additional standards for Uponor AquaPEX tubing and associated fittings include:
• ANSI/NSF Standard 14 “Plastics Piping System Components and Related Materials”
• ANSI/NSF Standard 61 “Drinking Water System Components — Health Effects”
• UL 1821 “Standard for Safety for Thermoplastic Sprinkler Pipe and Fittings for Fire Protection Service” (½" Uponor AquaPEX® only)


What temperature and pressure ratings does Uponor PEX carry?
Uponor PEX carries the following hydrostatic temperature and pressure ratings:
• 200°F at 80 psi (93.3°C at 5.51 bar)
• 180°F at 100 psi (82.2°C at 6.89 bar)
• 120°F at 130 psi (49°C at 9 bar) (½" Uponor AquaPEX® tubing only)
• 73.4°F at 160 psi (23°C at 11 bar)


What listings does Wirsbo hePEX tubing have?
Wirsbo hePEX™ tubing has the following listings:
• UL
• NSF-rfh


What code approvals does Wirsbo hePEX tubing have?
• NBC of Canada


What fire-rated assemblies does Wirsbo hePEX tubing have?
In the United States
• Tested in accordance with ASTM E119/UL 263
• G573 – Two-hour Hambro floor/ceiling assembly
• K913 – Two-hour concrete floor/ceiling assembly
• L557 – One-hour wood frame floor/ceiling assembly
• U372 – One-hour wood frame wall assembly
• V444 – One-hour steel stud wall assembly
In Canada
• Tested in accordance with CAN/ULC S101
• G573 – Two-hour Hambro floor/ceiling assembly
• UW/WA 60-01 – One-hour steel stud wall assembly
• UW/WA 60-02 – One-hour wood frame wall assembly
• WC/FCA 60-01 – One-hour wood frame floor/ceiling assembly
• WC/FCA 120-01 – Two-hour concrete floor/ceiling assembly
• WC/FCA 120-02 – Two-hour concrete floor/ceiling assembly


What is the Warnock Hersey Plenum Rating for Wirsbo hePEX?
• 25 flame spread/50 smoke developed (plenum rated) to ASTM E84:
o ½" and ¾" with spacing of 18" between each run of tubing
o 1" through 2" when insulated with ½" fiberglass insulation
• CAN/ULC S102.2:
o ½" through 1" with spacing of 18" between each run of tubing
o 1¼" through 2" when insulated with ½" fiberglass insulation


What code approvals does Uponor AquaPEX tubing have?
• NPC of Canada
• NBC of Canada


What listings does Uponor AquaPEX tubing have?
Uponor AquaPEX® tubing has the following listings:


What fire-rated assemblies does Uponor AquaPEX tubing have?
• G573 – Two-hour Hambro floor/ceiling assembly
• K913 – Two-hour concrete floor/ceiling assembly
• L557 – One-hour wood frame floor/ceiling assembly
• U372 – One-hour wood frame wall assembly
• V444 – One-hour steel stud wall assembly


What is the Warnock Hersey Plenum Rating for Uponor AquaPEX?
• 25 flame spread/50 smoke developed (plenum rated) to ASTM E84:
o ½" and ¾" with spacing of 18" between each run of tubing
o 1" through 2" when insulated with ½" fiberglass insulation
• CAN/ULC S102.2:
o ½" through 1" with spacing of 18" between each run of tubing
o 1¼" through 2" when insulated with ½" fiberglass insulation


What is PEX tubing?
PEX (crosslinked polyethylene) tubing is a specially designed plastic tubing with distinctive properties that make it ideal for radiant floor heating and plumbing systems. Uponor produces PEX-a tubing, which is considered the superior type of PEX.


What is Wirsbo hePEX™?
Wirsbo hePEX™ is crosslinked polyethylene (PEX-a) heat-transfer tubing that features a patent-pending oxygen-barrier coating technology for closed-loop hydronic heating and cooling applications.


What is Uponor AquaPEX®?
Uponor AquaPEX is crosslinked polyethylene (PEX-a) tubing for potable-water plumbing applications.


What's the difference between PEX-a, PEX-b and PEX-c tubing?
Currently, three methods for producing crosslinked polyethylene (PEX) tubing exist:

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

All three processes generate tubing that is crosslinked to varying degrees, and are acceptable for potable water distribution applications according to ASTM F876 and F877 standards. Uponor manufactures Engel-method PEX-a tubing. The PEX tubing industry considers this tubing 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 the other methods), resulting in a more uniform product with no weak links in the molecular chain. Learn more about why PEX-a tubing is better.


Do you offer a warranty on your tubing?
Yes. We are so confident of the quality of our PEX-a tubing, we offer a 25-year limited warranty or a 30-year warranty when installed by a member of our Home Comfort Team (HCT).


Why is an Uponor PEX plumbing system a better choice for plumbing than copper?
First of all, it's a clean and quiet water distribution system. Additionally, Uponor's plumbing system features Uponor AquaPEX® tubing, which is corrosion resistant. Aggressive water and soil, common across the United States, is not kind to copper plumbing and pinhole leaks can occur in copper as a result of these aggressive conditions. Additionally, An Uponor PEX plumbing system is quiet. No more singing pipes and water hammer typically heard with metal plumbing systems.


How long has Uponor PEX been used in plumbing systems?
Uponor PEX tubing has been used worldwide in plumbing and radiant heating systems for more than 30 years, longer than any other flexible system on the market.


Are ProPEX® fittings available for 3" Uponor AquaPEX?
Currently, we do not offer 3" ProPEX fittings. However, we are looking to expand our offering to include that in the future.


Is 3" Uponor AquaPEX approved for high-rise residential construction?
You can use 3" Uponor AquaPEX in high-rise construction areas where fire-resistive construction is not required. Current assemblies are only applicable for up to 2" Uponor AquaPEX tubing. Uponor is currently evaluating which fire-resistive construction assemblies to test for 3" Uponor AquaPEX.


Can 3" Uponor AquaPEX be used in a return air plenum?
Uponor is currently in the process of testing 3" AquaPEX tubing to ASTM E84 and CAN/ULC S102.2.


Is it true that 3" Uponor AquaPEX tubing is dimensionally smaller than copper pipe?
Yes. Both copper pipe and PEX tubing’s outside diameters are controlled to the same dimensions, and because PEX has a thicker wall, the inside diameter of the PEX tubing is smaller. However, PEX tubing is capable of handling higher velocities because it is not subject to erosion like copper pipe, thus providing similar flow rates.


Can you use 3" Uponor AquaPEX tubing in riser applications?
Yes, 3" Uponor AquaPEX is appropriate for riser applications. However, the combination of internal water pressure and water-column height cannot exceed the maximum pressure ratings for a given temperature.


Are there specific requirements for supporting 3" Uponor AquaPEX tubing?
Yes, 3" Uponor AquaPEX tubing requires support every 32 inches on horizontal runs. However, you can increase spacing by using a support channel. The 3" tubing also requires support at each floor and mid-story guide on vertical risers.


Does 3" Uponor AquaPEX require expansion loops?
For aboveground installations, use an expansion loop every 50 feet of tubing in hot-water applications and every 100 feet of tubing in coldwater applications. For belowground installations, snake the tubing in the trench to accommodate for expansion and contraction.


How do graywater systems work?
In a graywater system, water is captured from sinks and showers into a holding tank where it goes through a filtering process. Then, specially designated purple tubing — the industry standard color for reclaimed water systems — distributes the filtered, reclaimed water from the holding tank out to laundry, toilets and irrigation systems.


What is the cost to add a graywater (reclaimed water) distribution system?
The cost can vary by region and building size, however, adding a dual potable/reclaimed water plumbing system can add minimal and sometimes even less cost compared to traditional plumbing systems.


Does a reclaimed water distribution system need a separate storage tank?
It depends on the application. While all reclaimed water systems require a filter tank to capture and sanitize the reclaimed water, the requirement for a separate storage tank depends on the specific plumbing application.


Has Uponor PEX tubing undergone extensive testing?
Yes, Uponor PEX has undergone 35 years of rigorous testing. In 1973, Uponor (then Wirsbo), submitted PEX tubing samples to an independent laboratory. For three decades, these samples underwent continuous hydrostatic tests at extreme temperatures and pressures — up to 203°F and 239 pounds per square inch. When the 30-year life cycle tests were concluded recently, not a single piece of Uponor PEX had experienced any breakdown or failure.


Can using AquaPEX Reclaimed Water tubing help meet LEED® or National Green Building Standard™ points?
Depending on your application, using AquaPEX Reclaimed Water tubing in a graywater system may help earn LEED® or National Green Building Standard™ points. (For further information, refer to or


What kind of cost savings does Pre-insulated AquaPEX offer?
On average, Uponor Pre-insulated AquaPEX saves approximately 37% over the two-step installation and insulation method.*
*Source: RS Means Construction Data


Can you use Pre-insulated AquaPEX in a plenum?
Pre-insulated tubing is not currently listed for installation in a plenum. Uponor is in the process of evaluating the product in this application.


Can you bury Pre-insulated AquaPEX?
Yes, provided the tubing is buried in an area away from contact with groundwater. Although the water will not compromise the integrity of the AquaPEX tubing or insulation, it will have a detrimental effect on the insulating value of the insulation.


Where can I use Pre-insulated AquaPEX?
Pre-insulated AquaPEX can be used in all areas of a potable water system.


Are there any accessories or guidelines for insulating connections (tees, ells, etc.) in conjunction with Pre-insulated AquaPEX?
The insulation can be pulled over the expanded ProPEX® Ring leaving only the fitting body un-insulated. Uponor does not offer insulation kits for the fittings; however, insulation kits are available in the industry if needed for your specific application.


Why is Uponor offering lead-free brass transition fittings and valves?
Uponor is responding to recent proposed and approved lead-level and lead-free legislation from states such as California and Vermont. For example, California’s lead-free legislation (AB1953) states that all metallic fittings, fixtures and any material that conveys potable tap (drinking) water must meet lead-level criteria at or below 0.25% by composition. In addition, these lead-free brass fittings also exceed the United States Safe Drinking Water Act.


When is lead-level legislation set to take effect?
California and Vermont have already approved their proposed lead-free legislation, which took effect Jan. 1, 2010. Once a state’s legislation is approved and takes effect, all suppliers of metallic potable water components must prove their products meet the lead-level criteria by complying with the minimum requirement from the National Sanitation Foundation (NSF) and displaying the NSF us-pw-G markings.


What lead-free products does Uponor offer?
Uponor offers a comprehensive line of sweat fittings, threaded fittings, stub-outs, valves and wall boxes that can plumb a building with up to 2" inlet. Combining these transition fittings with our PEX tubing, extensive EP offering and ProPEX Out-of-the-Wall support system offers the industry’s first complete lead-free plumbing system from inlet to faucet.


Does the lead-free requirement affect Uponor’s PEX tubing or EP fittings?
No, Uponor’s PEX tubing and EP fittings contain no lead-level concerns.


What kind of fittings does 3" Uponor AquaPEX® use?
Our 3" Uponor AquaPEX® tubing uses WIPEX™ fittings which transition PEX tubing to male NPT threaded adapters.


Are Uponor lead-free brass fittings approved for direct burial in soil?
Yes, these fittings are approved for direct burial in soil and also replace our DZR brass fitting offering.


Does Uponor offer 3" tees, elbows and couplings?
One end of the WIPEX fitting for 3" Uponor AquaPEX connects to the PEX tubing; the other end is a 2½" male NPT adapter. This adapter will connect to any 2½" brass female NPT tee, elbow or coupling that is readily available from your wholesale distributor. Be sure to
use a brass alloy suitable for the application.


What are WIPEX™ fittings?
Extensively used in North America and Europe, especially for underground pre-insulated pipe systems, WIPEX fittings are manufactured from dezincification-resistant (DZR) brass, and are specifically designed for connecting 1" to 4" Uponor PEX tubing. The WIPEX fitting features an eccentric outer sleeve — for easier grip and an even force when inserting the tubing — and an inner sleeve with a threaded profile and O-ring to ensure a secure, tight seal.


How are WIPEX fittings made?
To create the fitting, first chamfer the inside of the tubing, then use a pair of pliers to dismount the outer sleeve and place it on the tubing. Then, mount the tubing on the inner sleeve and tighten the fitting with a wrench. For complete instructions, refer to the WIPEX Fittings Instruction Sheet.


What is the maximum operating pressure and temperature for WIPEX fittings?
The maximum operating pressure and temperature for WIPEX fittings is 87 psi at 203°F.


What tools are required for WIPEX fittings?
WIPEX fittings only require a chamfering tool, a simple pair of pliers and a wrench.


Are WIPEX fittings approved for potable water use?
Yes, WIPEX fittings are listed for compliance to NSF 61 for potable water use.

Radiant Cooling

What does the term radiant cooling refer to?
Radiant cooling refers to any system where surrounding surface temperatures are lowered as means of removing sensible heat gain and thus contributing to thermal comfort.


What exactly does a radiant cooling system consist of?
A hydronic radiant cooling system is an installation of embedded tubes or surface mounted panels that are designed to absorb and remove energy from a space, 50% to 80% of which is radiant energy. Just as in heating, a radiant cooling system uses the structure and surfaces of an area to transfer energy. In radiant heating systems, the energy moves away from the heated surface towards the cooler area. In radiant cooling systems, the energy moves towards the cooled surface from the warmer area.


Can the same system be used for a radiant floor heating and a radiant floor cooling system?
Yes, a floor cooling system should primarily be used where the system also will be used for heating in winter. Design a radiant heating and cooling system to maximize the cooling capacity.


Are there different types of radiant cooling?
Yes. Specifically there are low mass and high mass radiant cooling systems. Low mass radiant systems circulate cool water in specialized panels or beams and typically operate during the occupied time; high mass systems cool the building structure (slab, walls, ceilings) during unoccupied time and provide the additional advantage of off-peak cooling and further reduction in energy costs.


How does radiant cooling work with new highly efficient technologies on the market today?
Because radiant surfaces are often cooled only 2 to 4 degrees below the desired indoor air temperature, there are many opportunities for innovative cooling sources such as night fluid cooling, ground-coupled hydronic loops, and indirect evaporative cooling.


What type of buildings offer the best opportunity for radiant cooling applications?
• Museums
• Institutional and educational facilities
• Office buildings
• Atrium areas
• Manufacturing facilities
• Retail spaces
• Hospitals and Healthcare facilities
• Dormitories, barracks and prisons
• Churches
• Airports


Does the cooling system work for both commercial and residential applications?
Radiant cooling works best where wet bulb gain in the building can be controlled by the air handling system. Most often this is found in commercial building, however, in some climates where relative humidity is lower and in larger residences, where relative humidity can be controlled; radiant cooling is an additional strategy to lower cooling costs.


Should I use Wirsbo hePEX™ or Uponor AquaPEX® for a radiant system?
It depends on the application. Typically you will want to use Wirsbo hePEX which features an oxygen barrier to protect ferrous components in a closed-loop hydronic radiant system.


Are there sustainable design advantages to a radiant cooling system?
Yes, there are very considerable LEED® advantages with radiant cooling systems. Including, but not limited to, peak loads that are reduced as a result of thermal energy storage in the panel structure, exposed walls and partitions. Additionally, radiant cooling systems can use ground and bay water because they operate at a higher supply chilled water temperature.


What are some of the considerations must be taken into account when designing a radiant floor cooling system?
A floor cooling system must be controlled to avoid condensation. This may be done by a supply water temperature controlled by the dew point temperature. It is possible to cool with a floor system, but the system should be used in conjunction with a supplemental system.


What is the maximum cooling capacity for most spaces?
The maximum cooling capacity for most spaces is less than 17 Btu/ft²/h (50W/m²). In spaces with direct sunshine on the floor (atriums, entrance halls, show rooms) the cooling capacity will be significantly higher, around 14 Btu/ft²/h.


Are the calculations that are used for radiant floor heating the same as the calculations for radiant cooling?
The heat transfer between the floor surface and the tubes is influenced by floor construction in the exact same physical way by floor cooling as by floor heating. Therefore the calculation of the cooling capacity can be based on the same method How about, how does a radiant cooling system work? Just in general without going too in depth.


What are the factors that can affect the cooling capacity of a radiant floor cooling system?
The cooling capacity of a floor system depends on the heat exchange between the floor surface and the space (convective and radiant heat exchange coefficient), the heat conduction between the floor surface and the tubes (floor surface material, type of concrete, slab thickness, spacing between tubes) and the heat transport by water (water flow rate, temperature difference between supply and return). Dew point, floor coverings, AUST (average uncontrolled surface temperature) and average water temperature are also factors that can affect the cooling capacity.


Do you need a supplemental ventilation system?
Yes, however the ducts can be smaller which saves structural height. Ventilation is necessary to address the latent load and bring in the required refresh air.


What is the significance of radiant cooling systems to the commercial environment?
Radiant cooling has gained recent popularity in Europe and North America because it offers the potential to reduce cooling energy consumption and to reduce peak cooling loads when coupled with building thermal mass.


Can radiant cooling help with the latent, or wet bulb load, in my building?
No. A phase change is required to address this load. This is accomplished by the ventilation system of the building. The ventilation system will also control the balance of the sensible load throughout the occupied time of the day


Do I need separate embedded tubes to heat and cool the building?
No, one system can both heat and cool, and in some climates in North America, the system may do both throughout the day as well as be designed to transport heat from one side of the building or the other.


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