The Best Systems
No one radiant heating system is ideal for all situations, but after
30 years of serving customers, a few systems and techniques stand
We like simple honest value, with no gimmicks or do-dads. Systems
should be reliable, long lasting, and easy to work on. They
should be energy efficient and environmentally responsible and they must
be affordable. The best radiant heating systems should offer the
The Best Systems Should Offer:
- Low initial cost
- Low operating cost
- Environmental sensitivity
- Energy efficiency
- Simple and easy to work on
- Compatibility with solar energy
- Appropriate for a do it yourself project
The Best Overall Heating System
Simplified Schematic of The Open Direct System
the Open Direct System
In light of the above, the best systems will use a high quality, high
efficiency hot water heater instead of a boiler. These systems
cost about half as much as one using a typical boiler system and yet
are much more efficient. They are a simple, ingenious way to make
radiant space heat, domestic hot water and even pick up some free
cooling, all within the same unit. If you use a boiler, you will incur
extra costs and miss out on some great opportunities.
Domestic hot water based heating systems are so affordable, they
make the exceptional comfort, high efficiency, and health benefits of
a radiant heating system available to everyone - not just the one
You can use the same water heater for your radiant heating
system that you use for domestic hot water!
There are two systems to choose from that use the domestic water
heater as the energy source for your radiant heating system, the indirect
system that uses a heat exchanger and the direct system
that does not.
Click here for more information about
radiant systems that use the domestic hot water heater as the heat
These radiant heating systems are arguably the best and most
efficient heating systems available.
Heating systems that are based upon the domestic water heater cost
about half as much as one using a typical boiler system and yet
are much more efficient. They are generally made of better
materials. They are a simple, ingenious way to make radiant
space heat, domestic hot water and even to pick up some free cooling,
all within the same unit. Properly designed domestic hot water based
systems meet all major codes and are exceptionally safe.
Because these systems operate at low temperature they are more
energy efficient and safer than systems using a boiler. The expense of
a boiler is also entirely eliminated, making these sytems more
affordable as well. Domestic hot water heater based heating systems
are even compatible with a solar energy assist.
These systems are sometimes labeled "controversial" by people in the
heating industry that want to sell you an old-school boiler system
that costs 2 to 3 times as much. We have the science
and happy customer feedback
to back up our systems. It is up to you to consider the source of any
Polaris Water Heater.
Note the giant stainless steel
flue for extra efficiency.
The Best Heating Unit
The Polaris heating unit is a water heater (not a boiler) that is
engineered to make space heat as well as domestic hot water. Because
it is engineered to make warm water instead of boiling hot water right
from the beginning, it is incredibly energy efficient - and
safer as well. The Polaris is all stainless steel. A huge submerged
stainless steel flue extracts just about every possible BTU of heat
from the flue gas. Standby losses are nearly eliminated.
Even with these benefits, the polaris costs far less than a similar
capacity boiler. It's a good value to buy, and a good value to
continue to operate over time.
Click here for more information about the
The Best Heat Exchanger Tubing
The least desirable place to cut cost is with tubing and fittings.
Heat exchanger tubing often goes into inaccessible places where it
would be difficult to replace. Is the material approved? Can you work
with it? Is it energy efficient? Do not use waterline that has been
retasked as radiant heating pipe. It is not worth it.
Here are some of the benefits to proper tubing selection:
to learn more about high efficiency radiant heating tubes.
- Higher heat output
- Less pumping cost
- Longer circuits possible
- Lower, safer operating temperatures
- More energy efficient
- Longer service life
- Lower electric bills
- Quieter operation
- Compatibility with solar heating and alternative energy.
The Best Detail for a Joisted Floor
View of a Joisted
Floor System "Staple-Up"
Many commonly offered systems on the market do not work very well,
or cost too much. The following details are very important for
performance and cost.
We recommend you heat the floor with tubing installed in the joist
spaces beneath the sub floor. Use 5/8" PEX with .070 wall thickness. Use
high efficiency tubing. Space the tubing 8" apart within a 16"
joist space. Use thinner gauge aluminum heat emission plates and use
them everywhere if possible.
The 5/8" tubing is larger than typical 1/2" material. It puts out
more heat and allows the system to operate with lower fluid
temperatures for longer life and better efficiency. The larger
size reduces pump work and allows longer circuits. Tubings which are
larger than 5/8" may be too difficult to work with.
The aluminum plate takes heat away from the tubing and distributes it
throughout the sub floor. Research shows that this detail is very
important. The plates support the tubing well and the improved
heat transfer is significant. Thinner aluminum plates have equivalent
performance as thicker plates with half the cost.
The aluminum material has a very important and often overlooked
property. Aluminum radiates much less heat into the air than other
materials. This property sharply reduces heat loss in the downward
direction (back loss) and has the effect of insulation. It is very
important to control heat loss in the wrong direction as these
losses can nullify most of the benefits of radiant heat.
Click here to
read our research report about aluminum heat emissions and heating
The radiant thermograph on the right shows a significant difference
in floor temperature when aluminum plates are used. The far
(orange/yellow) side of the floor has aluminum plates, the rest of
the floor has radiant tubing but no heat plates. You can see from the
legend in the right of the photo that this represents a significant
difference in temperature.
Comparison of radiant tubing effect with and without aluminum heat
The radiant thermograph (right) shows that the aluminum plates
(blue) emit much less heat than the surrounding areas (red, orange)
even though they are at a much higher temperature. This
property means that the plates are taking the heat away from the
tubing, distributing it throughout the floor, and then, making the
heat go in the right direction.
Thermograph of operating aluminum plates
Feel free to contact customer service technicians if you would like
more information about these details. Customers may also request
a research report.
The Best Details for Slab on Grade Construction
Our experience and research indicates that under slab insulation is
most important at the perimeter and less important in the center of
the building. Insulation should be extruded polystyrene.
We know of no other acceptable material. In cold climates, it should
be 2 inches thick at the perimeter and may taper off to 1 inch as it
goes inward towards the center of the building. Insulation should
extend 12 feet from the perimeter towards the center in cold climates
but can be reduced to 6 feet in warmer climates. Our experience
indicates that failure to insulate properly is one of the most
serious mistake that you can make.
"Rod" type reinforcement is preferred over the "mesh" type because of
overall strength and workability. Put down half of the
reinforcing first and set it on "chairs" or bricks. Then lay out
the tubing. Lay out the other half of the reinforcing on top of
the tubing and tie everything together. It will be easier to lay
out the tubing (because only half of the tubing is placed), and the
tubing will be well protected by the reinforcing. The reinforcing will
carry heat away from the tubing, and the reinforcing is generally well
placed with half above the centerline of the slab and the other half
placed a little beneath. Fiberglass reinforcing fibers are
not a substitute for steel reinforcing.
Tubing Size and Spacing
If the slab is to be of any significant size, (500 square ft or
larger), a larger diameter tubing is preferred (up to 7/8" diameter).
A larger tube (within reason) will put out more heat, reduce pump work
and enable longer circuit lengths. Tube spacing may be spaced 24" on
center in very efficient and stable environments (such as basements).
A 16" spacing is more typical for reasonably efficient
residential construction and 12" spacing will provide a little more
heat and a more rapid response time.
Detailed research (DOE) has shown that 7/8" PEX tubing with 0.70"
wall thickness and a circuit length of 200 feet is about ideal.
The electrical energy consumption of the pumps will be as low as
possible and the flow will be just slightly turbulent. The
temperature drop will be about 10 degrees F from inlet to outlet. This
is ideal, but different designs can still produce satisfactory
The Best Solar Heating System
If you start out with a domestic hot water based heating system it
is easy to add a solar supplement; either now or in the future. Solar
domestic water heaters are well proven and accepted.
The "Solar Option Two" heating system is an extension of successful
solar domestic hot water applications. In the right place, the
solar domestic water heaters have been successful as long as the work
is done right and the domestic hot water production is valued (schools
and churches are often not appropriate, residential construction is
The radiant heating system is designed to use the domestic water
heater as the energy source and additional solar panels are
provided so that some contribution to space heating or other energy
needs can be made. The overall system may be limited by the ability of
the house and system to store heat.
Schematic diagram of Solar Option Two
This system, either as a solar "assist" or in a building that
already has its own "thermal mass" is cost effective in all areas of
the Continental United States when it is planned thoughtfully.
here to visit our solar heating website
The Best Pumping Design
Every month of the heating season, you must pay the electric
company for the energy that your pumps use. It is most efficient to
use a single individual pump for each heating zone. The alternative
would be to use one large pump and individual zone control valves.
This is a common practice, but it is not good design. The pump
must be sized so it is large enough to provide adequate flow when all
of the zones are calling for heat but most of the time, only one or
two heating zones are calling. The pump is too large for the task
resulting in a waste of electricity and unnecessary wear and
strain on the system.
A zone valve costs nearly as much as a small pump so there is really
no money to be saved by using them. Small pumps are mass produced and
cost much less than larger pumps.
Radiantec provides adjustable three speed pumps that can be set to
meet your needs with the lowest amount of electrical use possible.