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Advantages of Radiant Heating Systems
Radiant Heat Systems offer many advantages over traditional heating systems.
Perhaps the most important advantage is the improved comfort level achieved with radiant heat
systems. Radiant Heat allows a room to be heated evenly by increasing the room's average
surface temperature. Another key benefit of radiant heat is energy efficiency.
Customers are able to save money on energy bills with Radiant Heat Systems due to comfort at
lower temperatures, room by room zoning, and lower water temperatures. Other advantages
include no visible components, noise reduction, and dependability.
Installation Methods
- Slab On or Below Grade
In this installation method the PEX Tubing may be either tied to a wire mesh or
rebar using wire or zip ties. If under-slab in being used, the PEX Tubing may be
stapled to the under-slab insulation. Edge Insulation should be used in this
application around the perimeter of the slab. Under-slab insulation should be used
when there is a high water table or the soil is moist, bedrock is present, floor
covering values exceed 2.0, or the linear feet of the perimeter is high in comparison
to the gross feet area.
To install the tubing without under-slab insulation, first place the wire mesh or
rebar on the compacted base material. Using wire or zip ties secure the tubing to the
rebar or wire mesh. Space the ties every three feet along straight runs. When making
180-degree turns, tie the tubing at the top of the arc and once on each side, 12
inches from the top of the arc. This prevents the tubing from floating up into the pour.
The tubing should be pressure tested to 60psi.
To install the tubing when there is under-slab insulation, you can use PEX Staples to
secure the tubing to the insulation. Staples should be placed every 3 feet along
straight runs, and when making 180-degree turns it should be treated similar to wire
mesh installation.
- Pour Over Existing Slab
This application is used in residential retrofit situations. An example of this is
finishing an existing basement. Under-slab insulation should be used in this
application, and the pour should be at least 1-1/2" thick. The pour should be ¾" over
the top of the tubing, so if 1" tubing is used, the pour should be greater than an
1-1/2" thick. In this application tubing is secured to a wire mesh or rebar in the same
manner as a slab installation. An alternative would be to staple the tubing to the
under-slab insulation. However, when making 180-degree turns, a tie or staple should be
placed at the top of the arc and 6" from the top of the arc (one on each side). Tubing
should be pressure tested to a minimum of 60psi.
Cap pours are possible in different applications and situations. Pours may be made over a
pre-cast plank, steel decking, a suspended wood floor, or a suspended wood floor with
sleepers. While these are not as popular as an over slab pour, they are still possible.
- Quik Trak Over a Wood Subfloor or Existing Slab
Quik Trak panels are plywood panels that have an aluminum underside. The panels
have a built-in groove for tubing to be placed in. This application is in residential
construction as an alternative to joist heating and over-pours. A minimum of R-19
insulation should be used between the floor joists beneath the floor. An air space
should be left between the insulation and the floor. When installing a radiant heat
system using Quik Trak, 5/16" hePEX Tubing must be used. The maximum loop length for
5/16" Tubing is 250'. Other sizes of PEX Tubing will not fit into the Quik Trak Panels.
To install Quik Trak panels, first lay the panels down on top of the wood sub-floor.
The panels should be placed perpendicular to the floor joists. The seams of the Quik
Trak should be staggered. After the panels are laid, the grooves of the panels should
be vacuumed to remove debris. Next, a thin bead of Quik Trak Sealant should be placed
throughout the length of each of the grooves. The sealant acts as an adhesive and promotes
good heat transfer from the tubing to the panel.
To install the tubing walk or step the tubing into the panel grooves. You may need to
use a rubber hammer to snap the tubing into the groove. To secure the panels to the
sub-floor use 1-1/4" screws or 1" staples. Start from the middle of the panel and work
to the ends, alternating from side to side. If the panels are being installed over an
existing slab a layer of 5/8" or ¾" plywood should be placed over the slab before
installing the Quik Trak. In this application 1" screws or staples should be used.
Different floor covering types are possible using Quik Trak. However, the most efficient
are hardwood, tile, and linoleum. Carpet floor covering installations will not be as
efficient, but are possible.
- Joist Heating using PEX Clips
This method is commonly used in new and retrofit installations. The installation
is not recommended for open-web truss construction. A minimum of R-11 Insulation should
be used even if the space below is heated. When the tubing is installed in a crawl
space, a minimum of R-19 insulation is recommended. Standard insulation is adequate,
foil faced insulation is not necessary. Install the insulation vertically to block
the joist cavity beneath. A small air space (2"-3") should be left between the
insulation and the sub-floor above. PEX Clips work with both ½" and 3/8" PEX tubing.
To install PEX tubing using Wirsbo PEX Clips, drill holes 1-1/4" minimum side by side
at the end of each joist cavity. The tubing should then be threaded in between the
floor joists, moving from one joist to the other as needed. After installing tubing in
the last joist bay, run the PEX straight back through the joist holes behind the first
set of holes. Return this end to the manifold and connect it.
Next screw the PEX Clips into the bottom of the sub-floor. The clips should be placed
8" on center in 16" joist bays, 6" on center in 12" joist bays. Install the loop
farthest from the manifold first by pulling the loop the length of the bay. Slack from
the loop hanging from the next bay can be borrowed. The clips should be placed every
three feet along the joist bay. Attach the clips with screws. The screws should be no
longer than ¾". Snap the tubing into the PEX Clips. This will suspend the tubing an
inch below the subfloor. Continue the process until all of the loops are attached.
- Joist Heating Using Joist Trak
Joist Trak installations can be done for new work and retrofit applications.
Joist Trak applications produce more heat with the same water temperature as compared to
joist heating without the panels. Insulation should be installed snug against the panels.
Tubing should be pressure tested to 60 psi. Joist Trak works with ½" and 3/8" PEX Tubing.
To install a radiant heat system using Uponor Wirsbo Joist Trak, use ¾" drywall screws to
attach the panels to the subfloor. Panels should be separated equidistant from the joists
in 16" joist bay. Leave about a foot at the end of joists to allow for tubing turns.
Leave an inch between the panels. Drill two holes at the end of the joist bay. Thread the
PEX Tubing in between the joists, moving from one joist cavity to the other as necessary.
After tubing is in the last bay, run PEX back through the joist holes behind the first set
of holes. This end of the PEX will be connected to the manifold. Install the loop farthest
away first, slack can be borrowed from the loop hanging from the next joist bay. Then snap
the tubing into the panels. Continue this process until all the loops are installed.
Tell Me What Items I need for my Radiant Heat System
The Following are a few items that you need to keep in mind for Radiant Heat System.
- PEX Tubing
- Manifolds & Connections
- Controls & Zoning
- Expansion Tanks & Air Eliminators
- Heat Sources
There are several things you will need to decide in order to purchase the correct materials
for your radiant heat system. The first decision that needs to be made is how you will be
installing the radiant heat system. For more information on this please click on this link
Radiant Heat Installation Methods.
After determining which installation method to use, you must now decide what size PEX Tubing to
use and how much PEX Tubing to use. In general you can use the formulas located on this
page: How much PEX tubing do I need? For more specific information read the paragraphs
written below.
- Amount, Size, and Type of PEX Tubing to Use
Wirsbo Quik Trak installations 5/16" tubing must be used and the tubing will
automatically be spaced 7" apart. When using 5/16" tubing the maximum loop length will
be 250'. To determine the amount of tubing to use for a Quik Trak Installation
multiply the square footage to be heated by 1.7. This number will represent the total
amount of tubing to be used for the system. For the amount of straight Quik Trak boards
multiply the square footage by .386. For the return Quik Trak Panels which go along the
walls of the space to be heated, multiply the square footage by .043.
Joist Heating installations can use either 3/8" or ½' PEX tubing. While ½" is generally
the standard size, 3/8" is becoming more popular due to its ease of installation.
Tube spacing in a joist heating application is determined by the distance between the
joists. Standard joist spacing is 16". Therefore tubing should be spaced 8" apart in
these systems (two runs per joist). To determine the amount of tubing for 8" spacing,
multiply the square footage of space being heated by 1.5.
There are two ways that PEX can be installed in joist bays. These two methods are Wirsbo
Joist Trak plates and suspended pipe systems. Joist Trak plates will allow a system to
run more efficiently by lowering the required supply temperature to the radiant heat system.
To determine the number of Wirsbo Joist Trak Panels required, multiply the total amount of
tubing needed by .85. Then divide this number by 4. This number represents the total
number of plates required. The alternative installation method is suspending the pipe
below the subfloor. Suspended pipe systems require PEX Clips to support the tubing below
the subfloor. To determine the number of PEX Clips needed divide the total amount of
PEX Tubing that is running in the joists by 4. This number represents the total number of
PEX Clips needed.
Slab, overpour, or other embedded radiant heat systems can use 3/8", ½", 5/8", ¾' or 1"
PEX Tubing. The size of the PEX Tubing will not change the heat output of the system.
However size does determine maximum loop length. Therefore for standard residential
applications ½" PEX tubing is most commonly used, but for commercial applications 5/8"
tubing or ¾" PEX may be used. Tube spacing is what determines heat output in these systems.
The closer the tubing is spaced the greater amount of heat that will be produced.
Depending upon the heat loss of the system, a proper spacing should be determined.
As a rule of thumb in colder climates where the space will be used as living space,
an average of 9" spacing should be used. For warmer climates or rooms that will not be
living spaces an average of 12" spacing should be used. Use the tubing chart below to
determine the amount of tubing needed after spacing has been determined.
Determining the amount of PEX Tubing required based on Spacing :
To determine the amount of tubing you need to heat a space follow these simple steps.
First determine the total square footage of floor space to be heated. Then for…
- 12" on center multiply square footage by 1.0
- 10" on center multiply square footage by 1.2
- 9" on center multiply square footage by 1.33
- 8" on center multiply square footage by 1.5
- 7" on center multiply square footage by 1.7
- 6" on center multiply square footage by 2.0
The tubing total you have includes only active loop length (the amount of tubing that is
actually in the room to be heated). You must add the leader length (the amount of tubing
that is required to get from the heated space to the manifold) to this total.
Whether an average of 9" spacing or 12" spacing is used, one simple rule should be followed.
Tubing should be spaced most closely in areas where heat loss is the greatest.
In general this occurs along exterior/exposed walls. So for spaces with an average of 9"
spacing, tubing should be spaced 6" apart along exposed walls for the first 3', and the
spacing should become wider as you come closer to the middle of the room.
Once the total amount of tubing has been found the number of loops should be determined.
The tubing can be divided by the maximum loop length to determine the number of loops.
See the table below for maximum loop lengths.
Maximum Loop Length for Each Size of PEX Tubing:
The table below shows each size of PEX Tubing with its maximum loop length.
| Size |
I.D. (inches) |
O.D. (inches) |
Volume per 100 ft. (Gallons) |
Max Loop Length |
| 5/16" |
.292 |
.43 |
.35 |
250' |
| 3/8" |
.35 |
.5 |
.5 |
250' |
| 1/2" |
.475 |
.625 |
.92 |
300' |
| 5/8" |
.574 |
.75 |
1.34 |
400' |
| 3/4" |
.671 |
.875 |
1.84 |
500' |
| 1" |
.862 |
1.125 |
3.03 |
750' |
Oxygen Barrier PEX Tubing:
Oxygen Barrier PEX tubing should be used in most radiant heat applications. This tubing
will prevent oxygen from exiting the tubing. If oxygen barrier tubing is not used for
systems with ferrous (cast iron/iron pumps, valves, boiler…) components, the system's
components will rust. Wirsbo Hepex Tubing, HydroPEX Oxygen Barrier Tubing, and ThermaPEX Tubing both have an oxygen
barrier. Non-Oxygen Barrier tubing such as Wirsbo Aquapex may be used in systems that
don't contain and will never contain ferrous components. If a system does contain these
components a heat exchanger may be used to separate the ferrous components. In general
in any new radiant heat system it is a good idea to use oxygen barrier PEX tubing.
Repairing Kinked Tubing:
For all PEX Tubing except PEX-AL-PEX Tubing, the following method may be used to repair kinks.
First straighten the kinked portion of the tubing. Then heat the kinked area using an electric heat gun. The tubing should be heated evenly to the surface in a gentle manner. An open flame should never be used. Apply the heat until the entire circumference of the tubing becomes transparent. Let the tubing cool to room temperature without disturbing it.
Loop Cad Display:
The following loop cad displays several key points regarding radiant heat tubing
installation.
Example of PEX Tubing layout
In this loop cad the manifold is placed on the left hand wall, equidistant from both ends of the building. The PEX tubing is
laid out in order to produce the most heat in areas of highest heat loss. Therefore, because the building has four exposed walls the
tubing is spaced 6" apart for the first two feet around the entire perimeter
of the building. As the PEX tubing is laid closer to the middle of the
room it is spaced farther apart, reaching a maximum of 12" spacing in
the middle of the room. In this example 1/2" ThermaPEX Oxygen Barrier
PEX Tubing will be used. This is a slab application, where a 4" pour
will be made over the tubing.
- Manifolds & Connections
There are many different radiant heat manifolds available on the market today.
These manifolds act as a hub of the PEX tubing loops used in your radiant heat system.
Manifolds can range anywhere from two to twelve ports. These manifolds can also be used to
create a zone within a radiant heat system. Manifolds generally come with two parts,
a supply manifold and a return manifold.
The supply manifold receives supply water from the heat source and disperses it into the
radiant heat system. In a closed loop system the return manifold collects the water from the
loops of the radiant heat system and runs them back through the return line to the heat source.
Connections - Supply & Return
There are two types of connections that need to be made to hook up a manifold to a radiant
heat system. First, the supply and return lines need to be connected to the supply and
return manifold. Supply and return lines are usually copper, threaded iron, or PEX and are
generally ¾' or 1". The appropriate adapters for each type of line must be used. The listings
below will help you choose the right adapters for a Wirsbo Manifold:
Type of Supply/Return Line - Adapter Needed
- ¾" Copper - A4143210
- 1" Copper - A4133210
- ¾" PEX Straight Connection (Compression) - A4143225 & A4020750
- ¾" PEX Elbow Connection (Compression) - A4153225 & A4020750
- ¾" PEX Straight Connection (ProPEX) - Q4143275
- ¾" PEX Elbow Connection (ProPEX) - Q4153275
- 1" PEX Straight Connection (ProPEX) - Q4143210
- 1" PEX Elbow Connection (ProPEX) - Q4153210
- ¾" Female Thread - A2133275
- 1" Female Thread- A2123210
**Remember you will need one adapter for the supply manifold and one adapter for the
return manifold.
Connections - Loops
Each manifold must be properly connected to the loops in a radiant heat system.
The ports of the supply and return manifolds must each be connected to the radiant system.
Therefore if there are 4 loops in your system, you will need 8 adapters.
Because PEX loops vary in their size you need to make sure you are purchasing the correct
adapters. The table below will help you choose the right adapters for Wirsbo Manifolds.
Type & Size of PEX in Loops - Adapter Needed
**Each of these adapters has R20 thread that will screw directly into Wirsbo Manifolds.
Controls & Zoning:
Controls act as the brains behind a radiant heat system.
Below is a list of the components that may be used in these systems.
Thermostats:
Thermostats allow you to communicate with your radiant heat system. Thermostats can be
extremely basic or very complex. They come completely manual, and non-programmable, or digital
programmable. As technology moves forward the functionality of thermostats becomes greater.
There are also thermostats that work in conjunction with sensors (floor or outdoor) to decide
when to turn on a radiant heat system, and how much heat to produce.
Pumps:
Pumps can be used in combination with a switching relay to control the flow of heat to several
different zones. Switching relays control the on/off functionality of pumps. Relays such as the
Taco SR series come in 1 pump, 2 pump, 3 pump, 4 pump, and 6 pump models. Therefore you can use
the SR506 switching relays and 6 007-F5 pumps to control six separate radiant heat zones.
Zone Valves:
Another way to control different radiant heat zones is with zone valves. Zone valves act as an
on/off control for each zone in a radiant heat system. This is a popular way to zone a radiant
heat system. Each manifold can be tied into a zone valve which is used to control a certain
zone. Zone valves come in many different varieties, sizes, and have many different
manufacturers. We carry several different models of zone valves from Taco and Honeywell.
A zone valve controller can be used in conjunction with zone valves to ease installation and
allow for a greater level of control in a heating system. Remember that if you are going to
use zone valves, you will still need a single pump to create a flow of water. This pump must be
large enough to account for the head-loss from all of the loops in the system.
Actuators:
Actuators are able to control the flow of water for an individual loop in a radiant heat system.
An actuator is screwed onto a radiant heat manifold and subsequently controls the valve on the
manifold. In this way the actuator can open or close the valve and thus turn a zone's heat on
or off. Remember that if you are going to use actuators, you will still need a single pump to
create a flow of water. This pump must be large enough to account for the head-loss from all of
the loops in the system. The main advantage to using actuators is that they allow installers
the ability to create multiple zones on a single manifold. For example, on an 8 loop manifold
with the use of actuators you can have one zone with 3 loops and one zone with 5 loops, or any
combination that is desired. Think of actuators as zone valves for the individual loops in a
radiant heat system. Actuators come in two different models: motorized and thermal. Motorized
actuators are fast opening and actually have a motor that opens and closes the valve on a
manifold. Thermal actuators are slow opening and don't contain a motor. Both types of
actuators accomplish the same task sufficiently.
Mixing Valves:
Mixing or tempering valves act to adjust the water temperature received from the boiler to
the desired temperature needed to operate a radiant heat system. For example if a boiler is
producing water at 200 degrees and the radiant heat system requires water that is 130 degrees,
the mixing valve will mix the boiler water and cold water to create the desired temperature.
Nearly every heating system requires a mixing valve. Mixing water can actually become quite
complicated with the use of motorized mixing valves and injection-mixing, installers are given
several different options. However, a simple mixing valve may be used as well.
Transformers:
Transformers act as the source of electricity for components in a radiant heat system. When
the wiring of a heating system is being done, one of the central components is a transformer.
As the name implies, a transformer can change electricity at one voltage to electricity of
another voltage. The Wirsbo 50 VA transformer works well with radiant heat systems.
Radiant Heat Schematics:
These Radiant Heat Schematics are designed to show samples of how radiant systems may be set
up. These are only some of the options, however many other systems are possible. To view
these schematics click on Radiant Heat Schematics.
PexSupply.com is RPA Certified
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PexSupply.com is an RPA (Radiant Panel Association) Certified
Company. Our radiant heat designer has passed the RPA radiant heat
designer exam. He is therefore an RPA certified radiant heat designer.
To help improve and ensure high performance standards throughout
the radiant industry, the RPA Certification Program recognizes those
technicians who demonstrate the experience and skills required to
design, install and maintain quality radiant heating systems. |
Custom Radiant Heat - Snow Melt System Design, Materials Quote, and Loop Cad Drawing
PexSupply.com offers custom radiant heat - snow melt design services. The design will be
done by a Radiant Panel Association certified designer. This certification involves classroom
training and an extensive certification exam. There is a $25 fee for this service. The
service works as follows…
- Fill out the form - See required info below
- Installation method.
- Room sizes.
- Wall sizes & r-values.
- Window sizes & r-values.
- Floor covering types & r-values.
- Zoning Preferences (how many zones & which rooms in each zone).
- Supply & return pipe size and type.
- Preferred heat source.
- What's Included
- Radiant Materials Quote.
- Includes pricing on PEX tubing, Manifolds, Fittings and other products needed for your
installation.
- Radiant Heat Design Details Report.
- Includes Heat loss information, Loop sizes and lengths, zoning information, and supply water
temperature.
- We will respond to you within 5 business days with either a phone call regarding questions on the design, or an e-mail with your design information.
**Please note if you need the design faster than 5 business days you must call (888) 757-4774 and let us know.
History of Radiant Heat
The History of Radiant Heat began with the Romans more than 2000 years ago. The Romans used
Radiant heat as an effective way to heat the floors of their villas and baths. Although not as
sophisticated as the systems of today, these systems allowed the wealthy Romans to heat spaces
in a comfortable manner.
In the twentieth century Radiant Heat began its resurgence. The English used hydronic radiant
heat systems early in the 20th century. These systems made use of the circulation of hot water
through iron pipes to heat buildings. The pipes were run under the floors of the buildings
similar to the way PEX Tubing is used in today’s systems.
While Radiant Heat was not sought after in the United States, major strides were being made
in Europe. In the 1960’s cross-linked polyethylene was developed. This product, also known as
“PEX” is used in the majority of installations of Radiant Heat Systems today. PEX was
stronger, more durable, had better memory, and was more flexible than the products that had
been used for radiant heat in the past. Therefore the development of PEX was a major turning
point in the history of radiant heat.
Radiant Heat continued to gain popularity throughout the latter half of the twentieth century
in Europe and the United States. Today Radiant Heat installations are growing at over 20% per
year in the US. These installations are used for residential and commercial applications.
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