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.

OPEN SYSTEM 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.

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.

HEAT EXCHANGER 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.

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BOILER 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 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

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DIRECT SYSTEM 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.

Radiantec R & DThe Best Overall SystemEngineered Tubing BenefitsInsulation and Heat MigrationStudy of Heat Transfer PlatesUS DOE ReportASES paper

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.

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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.

Installation ManualsDesign & Construction ManualOpen Direct SystemInstalling the Closed SystemInstalling the Indirect SystemInstalling tubing for a concrete slabInstalling tubing between floor joistsInstalling tubing in a subfloorInstalling tubing in the ceilingInstalling tubing in the wallsInstalling a heated towel rackInstalling Radiantec ControlsDoing your own tubing layoutRadiantec Basic Solar DomesticWater Heater Installation ManualRadiantec Basic Solar DomesticWater Heater Owners Manual

Installation ManualsDesign & Construction ManualOpen Direct SystemInstalling the Closed SystemInstalling the Indirect SystemInstalling tubing for a concrete slabInstalling tubing between floor joistsInstalling tubing in a subfloorInstalling tubing in the ceilingInstalling tubing in the wallsInstalling a heated towel rackInstalling Radiantec ControlsDoing your own tubing layoutRadiantec Basic Solar DomesticWater Heater Installation ManualRadiantec Basic Solar DomesticWater Heater Owners Manual

DOMESTIC HOT WATER HEATER 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.

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.

INDIRECT SYSTEM 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.

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.

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.

The Best Overall SystemRadiant Heating SystemsClosed SystemIndirect SystemOpen Direct SystemWater Heater heat sourceCost Saving BenefitsEnvironmental BenefitsAbout Building CodesProblems w/a code official?

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.

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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.

Radiantec R & DThe Best Overall SystemEngineered Tubing BenefitsInsulation and Heat MigrationStudy of Heat Transfer PlatesUS DOE ReportASES paper

Shop OnlineAbout our SelectionPricing InformationAffordabilityDo It YourselfInstallation PackagesIndividual Component PricesBallpark EstimatesSample Project CostQuick Quote FormFull Quote FormTax Credits are PossibleICC ES Evaluation Report

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

Installation ManualsDesign & Construction ManualOpen Direct SystemInstalling the Closed SystemInstalling the Indirect SystemInstalling tubing for a concrete slabInstalling tubing between floor joistsInstalling tubing in a subfloorInstalling tubing in the ceilingInstalling tubing in the wallsInstalling a heated towel rackInstalling Radiantec ControlsDoing your own tubing layoutRadiantec Basic Solar DomesticWater Heater Installation ManualRadiantec Basic Solar DomesticWater Heater Owners Manual

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

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.

Under Sink Guardian® Thermostatic Mixing Valve, Series/Model: Series LFUSG-B, Nominal Size: 3/8 IN, Connection Type: Male Compression, Ports/Ways: 4-Port, Pressure Rating: 30 - 150 PSI, Flow Rate: 0.25 GPM Minimum, Temperature Rating: 80 - 120 DEG F, 120 - 180 DEG F Hot Inlet, 39 - 80 DEG F Cold Inlet, 5 DEG F Minimum Inlet Temperature Differential, Brass Body Material, Trim Material: Buna-N Disc, Seal Material: Buna-N O-Ring, Industry Standards: ASSE Standard 1070, IAPMO Certified, cUPC Listed, 3-3/16 IN Width, 3-3/8 IN Height, Lead Free: Yes

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.

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.

Quote Cover LetterTake the Next StepRequest a BrochureQuick Quote FormFull Quote FormCustomer TestimonialsAbout our ProductsFreq Asked Questions

Quote Cover LetterTake the Next StepRequest a BrochureQuick Quote FormFull Quote FormCustomer TestimonialsAbout our ProductsFreq Asked Questions

For more information call 1 800-451-7593 | FAX 802-626-8045 | PO Box 1111, Lyndonville, VT 05851   | Terms & Conditions | Privacy Policy

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.

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.

The Best Overall SystemRadiant Heating SystemsClosed SystemIndirect SystemOpen Direct SystemWater Heater heat sourceCost Saving BenefitsEnvironmental BenefitsAbout Building CodesProblems w/a code official?

Our Systems are Code Compliant. Ask your tech for more information concerning your specific application, but in general, here is some relevant information:

This 3/8 IN under sink guardian® lead-free thermostatic mixing valve is used in commercial and residential applications to control the hot water temperature and minimize the potential for accidental scalding. It is suitable for kitchen and bath installations where the water delivered to the fixtures is intended for bathing or washing. The double throttling design controls both the hot and cold water supply to the mixed outlet. This valve consists of a lead-free brass body, 3/8 in male compression fittings, copper thermostat, check valves, integral strainer with 40 mesh stainless steel screens, and a tamper resistant locking cap. The maximum working pressure is 150 PSI (10.3 BAR). The water temperature can be field adjusted between 80 - 120 DEG F (27 - 49 DEG C). The recommended maximum temperature is 110 DEG F (43 DEG C).

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

Radiantec R & DThe Best Overall SystemEngineered Tubing BenefitsInsulation and Heat MigrationStudy of Heat Transfer PlatesUS DOE ReportASES paper

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.

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.

Shop OnlineAbout our SelectionPricing InformationAffordabilityDo It YourselfInstallation PackagesIndividual Component PricesBallpark EstimatesSample Project CostQuick Quote FormFull Quote FormTax Credits are PossibleICC ES Evaluation Report

The Best Overall SystemRadiant Heating SystemsClosed SystemIndirect SystemOpen Direct SystemWater Heater heat sourceCost Saving BenefitsEnvironmental BenefitsAbout Building CodesProblems w/a code official?