1 (800) 451-7593


Our Radiant Heating Systems

A Description of Several Types of Radiant Systems
Including Our Preferred System.

Think Outside the Box
There are many ways to take advantage of the benefits of radiant heating and cooling. Some radiant floor heat system concepts are at least 100 years old. Our radiant heating systems are newer and more innovative. We urge you to at least take a look at these modern systems. The newer and more innovative floor heating systems can offer significant advantages.

Please note that Radiantec often recommends the use of domestic water heaters instead of expensive boilers. Click here for more information about that use. This is an opportunity to save thousands of dollars and still have a better and more energy efficient radiant floor heating system.


(both heat and domestic hot water are provided directly from the same heating unit)

The “Open Direct Radiant System” is a significant breakthrough in radiant heating design. The Open Direct Radiant System offers unprecedented efficiency with a highly affordable first cost and is our preferred system of all radiant heating systems. It is one single system that operates in two different and distinct ways. When floor heat is called for, the pump comes on and water flows out of the tank, through the radiant floor heating zone and back to the tank. When domestic hot water is wanted, water flows out of the tank and goes to the fixture. All water in the system remains potable.

It is arguably the most energy efficient and environmentally friendly heating system in the world.

It is one of the very few exceptions to the rule that better things cost more. You literally get a much better system for a lot less money.


Open Direct Legend

Open Direct System Energy Efficiency Benefits.

  • The “Open Direct System” uses radiant heating which is fundamentally more energy efficient.
  • Dual use designs have less than ½ standby losses of two independent methods. One set eliminated and the other reduced because of efficient utilization.
  • Lower first cost presents the opportunity to buy a better, more efficient unit.
  • The “Open Direct System” is compatible with solar.
  • Domestic water heaters are potentially more efficient than a boiler. They can operate at low temperatures and they enable condensation of the flue gasses. Be aware that these benefits are only available with quality water heaters and may not be realized with cheap models.
  • Cold water pre heat provides limited free cooling by the detail where cold replacement water passes through the tubes in the floor before it goes to the tank.
  • The tank enables a huge heat exchanger for the flue.

Open Direct System Environmental Benefits.

  • Lower fuel consumption
  • IF YOU CONDENSE THE STEAM IN THE EXHAUST DOWN TO WATER, YOU CAN PICK UP ANOTHER 10% IN EFFICIENCY. Significant amounts of the pollutants will dissolve in the water and they go harmlessly down the drain instead of polluting the air.

Other benefits of the “Open Direct” System

Our Open Direct System is Exceptionally Affordable

  • Our design is simple & elegant
  • The design uses a water heater for dual purposes
  • No boiler saves thousands of dollars</;i>
  • Our design uses fewer parts
  • Easy installation saves labor cost
  • Energy Efficiency saves fuel costs.

Easy to Install

Our Open Direct System has a simple design and low number of parts compared to other systems.

Easy to Work On

The simplicity of our design and the ease with which you can find our parts in any hardware store make this system no problem for a handyman or the Do-It-Yourselfer.

Simple to Maintain

Our design is easy to understand. Our radiant system operates at a much lower temperature than those of a furnace so it’s safer to work on, and our materials last a long time so they don’t need constant upkeep.

Easy to Get Parts For

Our design is straightforward and our parts are common. That might not sound like a good thing, but it is! You can find the parts we use at any good hardware store, no special ordering required.

Fewer Parts

Because our design is simple and we use a water heater for heat and domestic hot water, our system is less complicated & uses fewer parts.

More Reliable

Our system has fewer moving parts, runs at lower temperatures than boiler systems, and offers stainless steel quality.

Longer Lasting

Lower operational temperatures, stainless steel construction, and high quality tubing equals a system that lasts and lasts.

Energy Efficient

Radiant heating is naturally energy efficient. Our system operates at lower temperatures so less fuel is needed to heat the water and our hot water heaters condense flue gasses to get maximum heating from your fuel.

Environmentally Friendly

Because we use condensing water heaters, our systems have lower emissions than others. Our systems also uses less fuel than a boiler system, and are compatible with solar.

Compatible with Solar

Our Open Direct System is compatible with solar. You can plan to install solar panels initially or at any time in the future. Check out our Solar Energy Library for more information about how to integrate solar panels into your radiant heating system.

Do It Yourself Friendly

Our Open Direct System is a simple, elegant design that uses easy to find common parts. Many of our customers choose to use our free design assistance and install the system themselves at great savings.
Read more about DIY installation here.


Our system runs at lower temperatures than systems with a boiler, making it inherently safer to install, to use, and to maintain.


We must note here that innovation is not always welcomed by those with special interests in the status quo. You must consider the source when you evaluate comments from those who profit from the sale of boilers. Low cost and simplicity is not always welcome. You cannot make a $5,000 profit from a $5,000 system. The use of water heaters in radiant heating applications is accepted by all major codes. There has never been even a single case of Legionnaires disease attributed to an open direct system.

Do not let lies from disgruntled competitors deprive you of what you are entitled to.


Click Here for more information about Radiantec’s Open Direct Radiant System.


(heating is provided indirectly by means of a heat exchanger)

When radiant floor heating is called for, domestic hot water is pumped to the heat-exchanger where the heat is transferred to the heating fluid on the other side. At the same time, the floor heating zone pump(s) comes on and circulates the heating fluid where it is needed.

A heat exchanger separates the radiant heating fluid from the potable water supply.  This allows a non-potable heating fluid (such as Anti-freeze) to be used. These radiant heating systems

Click here to read more about Radiantec’s Indirect System.


Indirect System


(This “traditional” system uses a boiler or water heater to heat water)

Closed radiant heating systems dedicate a boiler or water heater exclusively for space heating. Then water (or glycol) circulates through the radiant floor tubing. When a boiler is used, this familiar and conventional approach is well accepted by building code officials.

Closed System

Click here for more information about Radiantec’s Closed System

Solar Radiant Heating Systems

Radiantec supports the use of solar energy whenever it is feasible and notes that solar efficiency has improved greatly in the past few years. The following graphic represents a solar domestic hot water based solar system that is particularly appropriate for radiant heating systems.


For more information on our solar heating technology, visit


If you see words and expressions that you are not familiar with, consult this section.

Understanding the meaning of the following phrases will make it easier to understand your heating system options.

A boiler is a heating device that is engineered to make very hot water (up to 250 degrees F, under pressure) for radiators and baseboards. Many boilers do not work well at lower temperatures and may need expensive controls to make the adjustment.

A domestic water heater makes moderate temperature water and a storage tank is typically provided. There is a potential for higher efficiency with a hot water heater because of lower operating temperature and lower exhaust gas temperature, but many low end water heaters do not take advantage of this potential.

A heat exchanger is a device that exchanges the heat from one fluid to another without a mixing of the fluids. A typical use would be to keep the potable domestic hot water separate from the boiler fluid.

A closed heating system is closed off from the environment and its heating fluid is only changed for maintenance.

An open system is one that is open to the atmosphere or one in which the heating fluid is replaced often.  A domestic water heater is an open system because the heated fluid is constantly changed. Open systems require different mechanicals and materials.

Potable means fit to drink.

A direct system uses the same water for both heating and domestic hot water for doing dishes, laundry, taking showers, etc. There is no separation between the two.

An indirect system is one in which the heat from the heating unit passes through a heat exchanger before it goes to the in floor heating tubes.